com.unity.netcode.gameobjects@1.2.0

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

Additional documentation and release notes are available at [Multiplayer Documentation](https://docs-multiplayer.unity3d.com).

## [1.2.0] - 2022-11-21

### Added

- Added protected method `NetworkBehaviour.OnSynchronize` which is invoked during the initial `NetworkObject` synchronization process. This provides users the ability to include custom serialization information that will be applied to the `NetworkBehaviour` prior to the `NetworkObject` being spawned. (#2298)
- Added support for different versions of the SDK to talk to each other in circumstances where changes permit it. Starting with this version and into future versions, patch versions should be compatible as long as the minor version is the same. (#2290)
- Added `NetworkObject` auto-add helper and Multiplayer Tools install reminder settings to Project Settings. (#2285)
- Added `public string DisconnectReason` getter to `NetworkManager` and `string Reason` to `ConnectionApprovalResponse`. Allows connection approval to communicate back a reason. Also added `public void DisconnectClient(ulong clientId, string reason)` allowing setting a disconnection reason, when explicitly disconnecting a client. (#2280)

### Changed

- Changed 3rd-party `XXHash` (32 & 64) implementation with an in-house reimplementation (#2310)
- When `NetworkConfig.EnsureNetworkVariableLengthSafety` is disabled `NetworkVariable` fields do not write the additional `ushort` size value (_which helps to reduce the total synchronization message size_), but when enabled it still writes the additional `ushort` value. (#2298)
- Optimized bandwidth usage by encoding most integer fields using variable-length encoding. (#2276)

### Fixed

- Fixed issue where `NetworkTransform` components nested under a parent with a `NetworkObject` component  (i.e. network prefab) would not have their associated `GameObject`'s transform synchronized. (#2298)
- Fixed issue where `NetworkObject`s that failed to instantiate could cause the entire synchronization pipeline to be disrupted/halted for a connecting client. (#2298)
- Fixed issue where in-scene placed `NetworkObject`s nested under a `GameObject` would be added to the orphaned children list causing continual console warning log messages. (#2298)
- Custom messages are now properly received by the local client when they're sent while running in host mode. (#2296)
- Fixed issue where the host would receive more than one event completed notification when loading or unloading a scene only when no clients were connected. (#2292)
- Fixed an issue in `UnityTransport` where an error would be logged if the 'Use Encryption' flag was enabled with a Relay configuration that used a secure protocol. (#2289)
- Fixed issue where in-scene placed `NetworkObjects` were not honoring the `AutoObjectParentSync` property. (#2281)
- Fixed the issue where `NetworkManager.OnClientConnectedCallback` was being invoked before in-scene placed `NetworkObject`s had been spawned when starting `NetworkManager` as a host. (#2277)
- Creating a `FastBufferReader` with `Allocator.None` will not result in extra memory being allocated for the buffer (since it's owned externally in that scenario). (#2265)

### Removed

- Removed the `NetworkObject` auto-add and Multiplayer Tools install reminder settings from the Menu interface. (#2285)

CHANGELOG.md

@@ -6,6 +6,130 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 Additional documentation and release notes are available at [Multiplayer Documentation](https://docs-multiplayer.unity3d.com).
 
+## [1.2.0] - 2022-11-21
+
+### Added
+
+- Added protected method `NetworkBehaviour.OnSynchronize` which is invoked during the initial `NetworkObject` synchronization process. This provides users the ability to include custom serialization information that will be applied to the `NetworkBehaviour` prior to the `NetworkObject` being spawned. (#2298)
+- Added support for different versions of the SDK to talk to each other in circumstances where changes permit it. Starting with this version and into future versions, patch versions should be compatible as long as the minor version is the same. (#2290)
+- Added `NetworkObject` auto-add helper and Multiplayer Tools install reminder settings to Project Settings. (#2285)
+- Added `public string DisconnectReason` getter to `NetworkManager` and `string Reason` to `ConnectionApprovalResponse`. Allows connection approval to communicate back a reason. Also added `public void DisconnectClient(ulong clientId, string reason)` allowing setting a disconnection reason, when explicitly disconnecting a client. (#2280)
+
+### Changed
+
+- Changed 3rd-party `XXHash` (32 & 64) implementation with an in-house reimplementation (#2310)
+- When `NetworkConfig.EnsureNetworkVariableLengthSafety` is disabled `NetworkVariable` fields do not write the additional `ushort` size value (_which helps to reduce the total synchronization message size_), but when enabled it still writes the additional `ushort` value. (#2298)
+- Optimized bandwidth usage by encoding most integer fields using variable-length encoding. (#2276)
+
+### Fixed
+
+- Fixed issue where `NetworkTransform` components nested under a parent with a `NetworkObject` component  (i.e. network prefab) would not have their associated `GameObject`'s transform synchronized. (#2298)
+- Fixed issue where `NetworkObject`s that failed to instantiate could cause the entire synchronization pipeline to be disrupted/halted for a connecting client. (#2298)
+- Fixed issue where in-scene placed `NetworkObject`s nested under a `GameObject` would be added to the orphaned children list causing continual console warning log messages. (#2298)
+- Custom messages are now properly received by the local client when they're sent while running in host mode. (#2296)
+- Fixed issue where the host would receive more than one event completed notification when loading or unloading a scene only when no clients were connected. (#2292)
+- Fixed an issue in `UnityTransport` where an error would be logged if the 'Use Encryption' flag was enabled with a Relay configuration that used a secure protocol. (#2289)
+- Fixed issue where in-scene placed `NetworkObjects` were not honoring the `AutoObjectParentSync` property. (#2281)
+- Fixed the issue where `NetworkManager.OnClientConnectedCallback` was being invoked before in-scene placed `NetworkObject`s had been spawned when starting `NetworkManager` as a host. (#2277)
+- Creating a `FastBufferReader` with `Allocator.None` will not result in extra memory being allocated for the buffer (since it's owned externally in that scenario). (#2265)
+
+### Removed
+
+- Removed the `NetworkObject` auto-add and Multiplayer Tools install reminder settings from the Menu interface. (#2285)
+
+## [1.1.0] - 2022-10-21
+
+### Added
+
+- Added `NetworkManager.IsApproved` flag that is set to `true` a client has been approved.(#2261)
+- `UnityTransport` now provides a way to set the Relay server data directly from the `RelayServerData` structure (provided by the Unity Transport package) throuh its `SetRelayServerData` method. This allows making use of the new APIs in UTP 1.3 that simplify integration of the Relay SDK. (#2235)
+- IPv6 is now supported for direct connections when using `UnityTransport`. (#2232)
+- Added WebSocket support when using UTP 2.0 with `UseWebSockets` property in the `UnityTransport` component of the `NetworkManager` allowing to pick WebSockets for communication. When building for WebGL, this selection happens automatically. (#2201)
+- Added position, rotation, and scale to the `ParentSyncMessage` which provides users the ability to specify the final values on the server-side when `OnNetworkObjectParentChanged` is invoked just before the message is created (when the `Transform` values are applied to the message). (#2146)
+- Added `NetworkObject.TryRemoveParent` method for convenience purposes opposed to having to cast null to either `GameObject` or `NetworkObject`. (#2146)
+
+### Changed
+
+- Updated `UnityTransport` dependency on `com.unity.transport` to 1.3.0. (#2231)
+- The send queues of `UnityTransport` are now dynamically-sized. This means that there shouldn't be any need anymore to tweak the 'Max Send Queue Size' value. In fact, this field is now removed from the inspector and will not be serialized anymore. It is still possible to set it manually using the `MaxSendQueueSize` property, but it is not recommended to do so aside from some specific needs (e.g. limiting the amount of memory used by the send queues in very constrained environments). (#2212)
+- As a consequence of the above change, the `UnityTransport.InitialMaxSendQueueSize` field is now deprecated. There is no default value anymore since send queues are dynamically-sized. (#2212)
+- The debug simulator in `UnityTransport` is now non-deterministic. Its random number generator used to be seeded with a constant value, leading to the same pattern of packet drops, delays, and jitter in every run. (#2196)
+- `NetworkVariable<>` now supports managed `INetworkSerializable` types, as well as other managed types with serialization/deserialization delegates registered to `UserNetworkVariableSerialization<T>.WriteValue` and `UserNetworkVariableSerialization<T>.ReadValue` (#2219)
+- `NetworkVariable<>` and `BufferSerializer<BufferSerializerReader>` now deserialize `INetworkSerializable` types in-place, rather than constructing new ones. (#2219)
+
+### Fixed
+
+- Fixed `NetworkManager.ApprovalTimeout` will not timeout due to slower client synchronization times as it now uses the added `NetworkManager.IsApproved` flag to determined if the client has been approved or not.(#2261)
+- Fixed issue caused when changing ownership of objects hidden to some clients (#2242)
+- Fixed issue where an in-scene placed NetworkObject would not invoke NetworkBehaviour.OnNetworkSpawn if the GameObject was disabled when it was despawned. (#2239)
+- Fixed issue where clients were not rebuilding the `NetworkConfig` hash value for each unique connection request. (#2226)
+- Fixed the issue where player objects were not taking the `DontDestroyWithOwner` property into consideration when a client disconnected. (#2225)
+- Fixed issue where `SceneEventProgress` would not complete if a client late joins while it is still in progress. (#2222)
+- Fixed issue where `SceneEventProgress` would not complete if a client disconnects. (#2222)
+- Fixed issues with detecting if a `SceneEventProgress` has timed out. (#2222)
+- Fixed issue #1924 where `UnityTransport` would fail to restart after a first failure (even if what caused the initial failure was addressed). (#2220)
+- Fixed issue where `NetworkTransform.SetStateServerRpc` and `NetworkTransform.SetStateClientRpc` were not honoring local vs world space settings when applying the position and rotation. (#2203)
+- Fixed ILPP `TypeLoadException` on WebGL on MacOS Editor and potentially other platforms. (#2199)
+- Implicit conversion of NetworkObjectReference to GameObject will now return null instead of throwing an exception if the referenced object could not be found (i.e., was already despawned) (#2158)
+- Fixed warning resulting from a stray NetworkAnimator.meta file (#2153)
+- Fixed Connection Approval Timeout not working client side. (#2164)
+- Fixed issue where the `WorldPositionStays` parenting parameter was not being synchronized with clients. (#2146)
+- Fixed issue where parented in-scene placed `NetworkObject`s would fail for late joining clients. (#2146)
+- Fixed issue where scale was not being synchronized which caused issues with nested parenting and scale when `WorldPositionStays` was true. (#2146)
+- Fixed issue with `NetworkTransform.ApplyTransformToNetworkStateWithInfo` where it was not honoring axis sync settings when `NetworkTransformState.IsTeleportingNextFrame` was true. (#2146)
+- Fixed issue with `NetworkTransform.TryCommitTransformToServer` where it was not honoring the `InLocalSpace` setting. (#2146)
+- Fixed ClientRpcs always reporting in the profiler view as going to all clients, even when limited to a subset of clients by `ClientRpcParams`. (#2144)
+- Fixed RPC codegen failing to choose the correct extension methods for `FastBufferReader` and `FastBufferWriter` when the parameters were a generic type (i.e., List<int>) and extensions for multiple instantiations of that type have been defined (i.e., List<int> and List<string>) (#2142)
+- Fixed the issue where running a server (i.e. not host) the second player would not receive updates (unless a third player joined). (#2127)
+- Fixed issue where late-joining client transition synchronization could fail when more than one transition was occurring.(#2127)
+- Fixed throwing an exception in `OnNetworkUpdate` causing other `OnNetworkUpdate` calls to not be executed. (#1739)
+- Fixed synchronization when Time.timeScale is set to 0. This changes timing update to use unscaled deltatime. Now network updates rate are independent from the local time scale. (#2171)
+- Fixed not sending all NetworkVariables to all clients when a client connects to a server. (#1987)
+- Fixed IsOwner/IsOwnedByServer being wrong on the server after calling RemoveOwnership (#2211)
+
+## [1.0.2] - 2022-09-12
+
+### Fixed
+
+- Fixed issue where `NetworkTransform` was not honoring the InLocalSpace property on the authority side during OnNetworkSpawn. (#2170)
+- Fixed issue where `NetworkTransform` was not ending extrapolation for the previous state causing non-authoritative instances to become out of synch. (#2170)
+- Fixed issue where `NetworkTransform` was not continuing to interpolate for the remainder of the associated tick period. (#2170)
+- Fixed issue during `NetworkTransform.OnNetworkSpawn` for non-authoritative instances where it was initializing interpolators with the replicated network state which now only contains the transform deltas that occurred during a network tick and not the entire transform state. (#2170)
+
+## [1.0.1] - 2022-08-23
+
+### Changed
+
+- Changed version to 1.0.1. (#2131)
+- Updated dependency on `com.unity.transport` to 1.2.0. (#2129)
+- When using `UnityTransport`, _reliable_ payloads are now allowed to exceed the configured 'Max Payload Size'. Unreliable payloads remain bounded by this setting. (#2081)
+- Performance improvements for cases with large number of NetworkObjects, by not iterating over all unchanged NetworkObjects
+
+### Fixed
+
+- Fixed an issue where reading/writing more than 8 bits at a time with BitReader/BitWriter would write/read from the wrong place, returning and incorrect result. (#2130)
+- Fixed issue with the internal `NetworkTransformState.m_Bitset` flag not getting cleared upon the next tick advancement. (#2110)
+- Fixed interpolation issue with `NetworkTransform.Teleport`. (#2110)
+- Fixed issue where the authoritative side was interpolating its transform. (#2110)
+- Fixed Owner-written NetworkVariable infinitely write themselves (#2109)
+- Fixed NetworkList issue that showed when inserting at the very end of a NetworkList (#2099)
+- Fixed issue where a client owner of a `NetworkVariable` with both owner read and write permissions would not update the server side when changed. (#2097)
+- Fixed issue when attempting to spawn a parent `GameObject`, with `NetworkObject` component attached, that has one or more child `GameObject`s, that are inactive in the hierarchy, with `NetworkBehaviour` components it will no longer attempt to spawn the associated `NetworkBehaviour`(s) or invoke ownership changed notifications but will log a warning message. (#2096)
+- Fixed an issue where destroying a NetworkBehaviour would not deregister it from the parent NetworkObject, leading to exceptions when the parent was later destroyed. (#2091)
+- Fixed issue where `NetworkObject.NetworkHide` was despawning and destroying, as opposed to only despawning, in-scene placed `NetworkObject`s. (#2086)
+- Fixed `NetworkAnimator` synchronizing transitions twice due to it detecting the change in animation state once a transition is started by a trigger. (#2084)
+- Fixed issue where `NetworkAnimator` would not synchronize a looping animation for late joining clients if it was at the very end of its loop. (#2076)
+- Fixed issue where `NetworkAnimator` was not removing its subscription from `OnClientConnectedCallback` when despawned during the shutdown sequence. (#2074)
+- Fixed IsServer and IsClient being set to false before object despawn during the shutdown sequence. (#2074)
+- Fixed NetworkList Value event on the server. PreviousValue is now set correctly when a new value is set through property setter. (#2067)
+- Fixed NetworkLists not populating on client. NetworkList now uses the most recent list as opposed to the list at the end of previous frame, when sending full updates to dynamically spawned NetworkObject. The difference in behaviour is required as scene management spawns those objects at a different time in the frame, relative to updates. (#2062)
+
+## [1.0.0] - 2022-06-27
+
+### Changed
+
+- Changed version to 1.0.0. (#2046)
+
 ## [1.0.0-pre.10] - 2022-06-21
 
 ### Added
@@ -18,7 +142,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 ### Changed
 
 - Updated `UnityTransport` dependency on `com.unity.transport` to 1.1.0. (#2025)
-- (API Breaking) `ConnectionApprovalCallback` is no longer an `event` and will not allow more than 1 handler registered at a time. Also, `ConnectionApprovalCallback` is now a `Func<>` taking `ConnectionApprovalRequest` in and returning `ConnectionApprovalResponse` back out (#1972)
+- (API Breaking) `ConnectionApprovalCallback` is no longer an `event` and will not allow more than 1 handler registered at a time. Also, `ConnectionApprovalCallback` is now an `Action<>` taking a `ConnectionApprovalRequest` and a `ConnectionApprovalResponse` that the client code must fill (#1972) (#2002)
 
 ### Removed
 
@@ -63,6 +187,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Removed `ClientNetworkTransform` from the package samples and moved to Boss Room's Utilities package which can be found [here](https://github.com/Unity-Technologies/com.unity.multiplayer.samples.coop/blob/main/Packages/com.unity.multiplayer.samples.coop/Utilities/Net/ClientAuthority/ClientNetworkTransform.cs) (#1912)
 
 ### Fixed
+
 - Fixed issue where `NetworkSceneManager` did not synchronize despawned in-scene placed NetworkObjects. (#1898)
 - Fixed `NetworkTransform` generating false positive rotation delta checks when rolling over between 0 and 360 degrees. (#1890)
 - Fixed client throwing an exception if it has messages in the outbound queue when processing the `NetworkEvent.Disconnect` event and is using UTP. (#1884)
@@ -116,10 +241,12 @@ Additional documentation and release notes are available at [Multiplayer Documen
 ## [1.0.0-pre.6] - 2022-03-02
 
 ### Added
+
 - NetworkAnimator now properly synchrhonizes all animation layers as well as runtime-adjusted weighting between them (#1765)
 - Added first set of tests for NetworkAnimator - parameter syncing, trigger set / reset, override network animator (#1735)
 
 ### Fixed
+
 - Fixed an issue where sometimes the first client to connect to the server could see messages from the server as coming from itself. (#1683)
 - Fixed an issue where clients seemed to be able to send messages to ClientId 1, but these messages would actually still go to the server (id 0) instead of that client. (#1683)
 - Improved clarity of error messaging when a client attempts to send a message to a destination other than the server, which isn't allowed. (#1683)
@@ -171,6 +298,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Removed `FixedQueue`, `StreamExtensions`, `TypeExtensions` (#1398)
 
 ### Fixed
+
 - Fixed in-scene NetworkObjects that are moved into the DDOL scene not getting restored to their original active state (enabled/disabled) after a full scene transition (#1354)
 - Fixed invalid IL code being generated when using `this` instead of `this ref` for the FastBufferReader/FastBufferWriter parameter of an extension method. (#1393)
 - Fixed an issue where if you are running as a server (not host) the LoadEventCompleted and UnloadEventCompleted events would fire early by the NetworkSceneManager (#1379)
@@ -185,6 +313,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Fixed network tick value sometimes being duplicated or skipped. (#1614)
 
 ### Changed
+
 - The SDK no longer limits message size to 64k. (The transport may still impose its own limits, but the SDK no longer does.) (#1384)
 - Updated com.unity.collections to 1.1.0 (#1451)
 - NetworkManager's GameObject is no longer allowed to be nested under one or more GameObject(s).(#1484)

Components/Interpolator/BufferedLinearInterpolator.cs

@@ -8,6 +8,7 @@ namespace Unity.Netcode
     /// Solves for incoming values that are jittered
     /// Partially solves for message loss. Unclamped lerping helps hide this, but not completely
     /// </summary>
+    /// <typeparam name="T">The type of interpolated value</typeparam>
     public abstract class BufferedLinearInterpolator<T> where T : struct
     {
         internal float MaxInterpolationBound = 3.0f;
@@ -24,7 +25,7 @@ namespace Unity.Netcode
         }
 
         /// <summary>
-        /// There’s two factors affecting interpolation: buffering (set in NetworkManager’s NetworkTimeSystem) and interpolation time, which is the amount of time it’ll take to reach the target. This is to affect the second one.
+        /// There's two factors affecting interpolation: buffering (set in NetworkManager's NetworkTimeSystem) and interpolation time, which is the amount of time it'll take to reach the target. This is to affect the second one.
         /// </summary>
         public float MaximumInterpolationTime = 0.1f;
 
@@ -73,7 +74,7 @@ namespace Unity.Netcode
         private bool InvalidState => m_Buffer.Count == 0 && m_LifetimeConsumedCount == 0;
 
         /// <summary>
-        /// Resets Interpolator to initial state
+        /// Resets interpolator to initial state
         /// </summary>
         public void Clear()
         {
@@ -85,6 +86,8 @@ namespace Unity.Netcode
         /// <summary>
         /// Teleports current interpolation value to targetValue.
         /// </summary>
+        /// <param name="targetValue">The target value to teleport instantly</param>
+        /// <param name="serverTime">The current server time</param>
         public void ResetTo(T targetValue, double serverTime)
         {
             m_LifetimeConsumedCount = 1;
@@ -159,6 +162,7 @@ namespace Unity.Netcode
         /// </summary>
         /// <param name="deltaTime">time since call</param>
         /// <param name="serverTime">current server time</param>
+        /// <returns>The newly interpolated value of type 'T'</returns>
         public T Update(float deltaTime, NetworkTime serverTime)
         {
             return Update(deltaTime, serverTime.TimeTicksAgo(1).Time, serverTime.Time);
@@ -170,6 +174,7 @@ namespace Unity.Netcode
         /// <param name="deltaTime">time since last call</param>
         /// <param name="renderTime">our current time</param>
         /// <param name="serverTime">current server time</param>
+        /// <returns>The newly interpolated value of type 'T'</returns>
         public T Update(float deltaTime, double renderTime, double serverTime)
         {
             TryConsumeFromBuffer(renderTime, serverTime);
@@ -222,6 +227,8 @@ namespace Unity.Netcode
         /// <summary>
         /// Add measurements to be used during interpolation. These will be buffered before being made available to be displayed as "latest value".
         /// </summary>
+        /// <param name="newMeasurement">The new measurement value to use</param>
+        /// <param name="sentTime">The time to record for measurement</param>
         public void AddMeasurement(T newMeasurement, double sentTime)
         {
             m_NbItemsReceivedThisFrame++;
@@ -241,6 +248,8 @@ namespace Unity.Netcode
                 return;
             }
 
+            // Part the of reason for disabling extrapolation is how we add and use measurements over time.
+            // TODO: Add detailed description of this area in Jira ticket
             if (sentTime > m_EndTimeConsumed || m_LifetimeConsumedCount == 0) // treat only if value is newer than the one being interpolated to right now
             {
                 m_LastBufferedItemReceived = new BufferedItem(newMeasurement, sentTime);
@@ -251,6 +260,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Gets latest value from the interpolator. This is updated every update as time goes by.
         /// </summary>
+        /// <returns>The current interpolated value of type 'T'</returns>
         public T GetInterpolatedValue()
         {
             return m_CurrentInterpValue;
@@ -259,36 +269,63 @@ namespace Unity.Netcode
         /// <summary>
         /// Method to override and adapted to the generic type. This assumes interpolation for that value will be clamped.
         /// </summary>
+        /// <param name="start">The start value (min)</param>
+        /// <param name="end">The end value (max)</param>
+        /// <param name="time">The time value used to interpolate between start and end values (pos)</param>
+        /// <returns>The interpolated value</returns>
         protected abstract T Interpolate(T start, T end, float time);
+
         /// <summary>
         /// Method to override and adapted to the generic type. This assumes interpolation for that value will not be clamped.
         /// </summary>
+        /// <param name="start">The start value (min)</param>
+        /// <param name="end">The end value (max)</param>
+        /// <param name="time">The time value used to interpolate between start and end values (pos)</param>
+        /// <returns>The interpolated value</returns>
         protected abstract T InterpolateUnclamped(T start, T end, float time);
     }
 
+    /// <inheritdoc />
+    /// <remarks>
+    /// This is a buffered linear interpolator for a <see cref="float"/> type value
+    /// </remarks>
     public class BufferedLinearInterpolatorFloat : BufferedLinearInterpolator<float>
     {
+        /// <inheritdoc />
         protected override float InterpolateUnclamped(float start, float end, float time)
         {
-            return Mathf.LerpUnclamped(start, end, time);
+            // Disabling Extrapolation:
+            // TODO: Add Jira Ticket
+            return Mathf.Lerp(start, end, time);
         }
 
+        /// <inheritdoc />
         protected override float Interpolate(float start, float end, float time)
         {
             return Mathf.Lerp(start, end, time);
         }
     }
 
+    /// <inheritdoc />
+    /// <remarks>
+    /// This is a buffered linear interpolator for a <see cref="Quaternion"/> type value
+    /// </remarks>
     public class BufferedLinearInterpolatorQuaternion : BufferedLinearInterpolator<Quaternion>
     {
+        /// <inheritdoc />
         protected override Quaternion InterpolateUnclamped(Quaternion start, Quaternion end, float time)
         {
-            return Quaternion.SlerpUnclamped(start, end, time);
+            // Disabling Extrapolation:
+            // TODO: Add Jira Ticket
+            return Quaternion.Slerp(start, end, time);
         }
 
+        /// <inheritdoc />
         protected override Quaternion Interpolate(Quaternion start, Quaternion end, float time)
         {
-            return Quaternion.SlerpUnclamped(start, end, time);
+            // Disabling Extrapolation:
+            // TODO: Add Jira Ticket
+            return Quaternion.Slerp(start, end, time);
         }
     }
 }

Components/NetworkAnimator.cs

@@ -1,14 +1,19 @@
 #if COM_UNITY_MODULES_ANIMATION
+using System;
 using System.Collections.Generic;
 using Unity.Collections;
 using Unity.Collections.LowLevel.Unsafe;
 using UnityEngine;
+#if UNITY_EDITOR
+using UnityEditor.Animations;
+#endif
 
 namespace Unity.Netcode.Components
 {
     internal class NetworkAnimatorStateChangeHandler : INetworkUpdateSystem
     {
         private NetworkAnimator m_NetworkAnimator;
+        private bool m_IsServer;
 
         /// <summary>
         /// This removes sending RPCs from within RPCs when the
@@ -31,20 +36,28 @@ namespace Unity.Netcode.Components
             m_SendParameterUpdates.Clear();
 
             foreach (var sendEntry in m_SendTriggerUpdates)
+            {
+                if (!sendEntry.SendToServer)
                 {
                     m_NetworkAnimator.SendAnimTriggerClientRpc(sendEntry.AnimationTriggerMessage, sendEntry.ClientRpcParams);
                 }
+                else
+                {
+                    m_NetworkAnimator.SendAnimTriggerServerRpc(sendEntry.AnimationTriggerMessage);
+                }
+            }
             m_SendTriggerUpdates.Clear();
         }
 
+        /// <inheritdoc />
         public void NetworkUpdate(NetworkUpdateStage updateStage)
         {
             switch (updateStage)
             {
                 case NetworkUpdateStage.PreUpdate:
                     {
-                        // Only the server forwards messages and synchronizes players
+                        // Only the owner or the server send messages
-                        if (m_NetworkAnimator.NetworkManager.IsServer)
+                        if (m_NetworkAnimator.IsOwner || m_IsServer)
                         {
                             // Flush any pending messages
                             FlushMessages();
@@ -124,6 +137,7 @@ namespace Unity.Netcode.Components
 
         private struct TriggerUpdate
         {
+            public bool SendToServer;
             public ClientRpcParams ClientRpcParams;
             public NetworkAnimator.AnimationTriggerMessage AnimationTriggerMessage;
         }
@@ -133,11 +147,23 @@ namespace Unity.Netcode.Components
         /// <summary>
         /// Invoked when a server needs to forward an update to a Trigger state
         /// </summary>
-        internal void SendTriggerUpdate(NetworkAnimator.AnimationTriggerMessage animationTriggerMessage, ClientRpcParams clientRpcParams = default)
+        internal void QueueTriggerUpdateToClient(NetworkAnimator.AnimationTriggerMessage animationTriggerMessage, ClientRpcParams clientRpcParams = default)
         {
             m_SendTriggerUpdates.Add(new TriggerUpdate() { ClientRpcParams = clientRpcParams, AnimationTriggerMessage = animationTriggerMessage });
         }
 
+        internal void QueueTriggerUpdateToServer(NetworkAnimator.AnimationTriggerMessage animationTriggerMessage)
+        {
+            m_SendTriggerUpdates.Add(new TriggerUpdate() { AnimationTriggerMessage = animationTriggerMessage, SendToServer = true });
+        }
+
+        private Queue<NetworkAnimator.AnimationMessage> m_AnimationMessageQueue = new Queue<NetworkAnimator.AnimationMessage>();
+
+        internal void AddAnimationMessageToProcessQueue(NetworkAnimator.AnimationMessage message)
+        {
+            m_AnimationMessageQueue.Enqueue(message);
+        }
+
         internal void DeregisterUpdate()
         {
             NetworkUpdateLoop.UnregisterNetworkUpdate(this, NetworkUpdateStage.PreUpdate);
@@ -146,33 +172,266 @@ namespace Unity.Netcode.Components
         internal NetworkAnimatorStateChangeHandler(NetworkAnimator networkAnimator)
         {
             m_NetworkAnimator = networkAnimator;
+            m_IsServer = networkAnimator.NetworkManager.IsServer;
             NetworkUpdateLoop.RegisterNetworkUpdate(this, NetworkUpdateStage.PreUpdate);
         }
     }
 
-
-
     /// <summary>
     /// NetworkAnimator enables remote synchronization of <see cref="UnityEngine.Animator"/> state for on network objects.
     /// </summary>
-    [AddComponentMenu("Netcode/" + nameof(NetworkAnimator))]
+    [AddComponentMenu("Netcode/Network Animator")]
     [RequireComponent(typeof(Animator))]
-    public class NetworkAnimator : NetworkBehaviour
+    public class NetworkAnimator : NetworkBehaviour, ISerializationCallbackReceiver
+
     {
-        internal struct AnimationMessage : INetworkSerializable
+        [Serializable]
+        internal class TransitionStateinfo
         {
-            // state hash per layer.  if non-zero, then Play() this animation, skipping transitions
+            public int Layer;
+            public int OriginatingState;
+            public int DestinationState;
+            public float TransitionDuration;
+            public int TriggerNameHash;
+            public int TransitionIndex;
+        }
+
+        /// <summary>
+        /// Used to build the destination state to transition info table
+        /// </summary>
+        [HideInInspector]
+        [SerializeField]
+        internal List<TransitionStateinfo> TransitionStateInfoList;
+
+        // Used to get the associated transition information required to synchronize late joining clients with transitions
+        // [Layer][DestinationState][TransitionStateInfo]
+        private Dictionary<int, Dictionary<int, TransitionStateinfo>> m_DestinationStateToTransitioninfo = new Dictionary<int, Dictionary<int, TransitionStateinfo>>();
+
+        /// <summary>
+        /// Builds the m_DestinationStateToTransitioninfo lookup table
+        /// </summary>
+        private void BuildDestinationToTransitionInfoTable()
+        {
+            foreach (var entry in TransitionStateInfoList)
+            {
+                if (!m_DestinationStateToTransitioninfo.ContainsKey(entry.Layer))
+                {
+                    m_DestinationStateToTransitioninfo.Add(entry.Layer, new Dictionary<int, TransitionStateinfo>());
+                }
+                var destinationStateTransitionInfo = m_DestinationStateToTransitioninfo[entry.Layer];
+                if (!destinationStateTransitionInfo.ContainsKey(entry.DestinationState))
+                {
+                    destinationStateTransitionInfo.Add(entry.DestinationState, entry);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Creates the TransitionStateInfoList table
+        /// </summary>
+        private void BuildTransitionStateInfoList()
+        {
+#if UNITY_EDITOR
+            if (UnityEditor.EditorApplication.isUpdating)
+            {
+                return;
+            }
+            TransitionStateInfoList = new List<TransitionStateinfo>();
+            var animatorController = m_Animator.runtimeAnimatorController as AnimatorController;
+            if (animatorController == null)
+            {
+                return;
+            }
+
+            for (int x = 0; x < animatorController.layers.Length; x++)
+            {
+                var layer = animatorController.layers[x];
+
+                for (int y = 0; y < layer.stateMachine.states.Length; y++)
+                {
+                    var animatorState = layer.stateMachine.states[y].state;
+                    var transitions = layer.stateMachine.GetStateMachineTransitions(layer.stateMachine);
+                    for (int z = 0; z < animatorState.transitions.Length; z++)
+                    {
+                        var transition = animatorState.transitions[z];
+                        if (transition.conditions.Length == 0 && transition.isExit)
+                        {
+                            // We don't need to worry about exit transitions with no conditions
+                            continue;
+                        }
+
+                        foreach (var condition in transition.conditions)
+                        {
+                            var parameterName = condition.parameter;
+                            var parameters = animatorController.parameters;
+                            foreach (var parameter in parameters)
+                            {
+                                switch (parameter.type)
+                                {
+                                    case AnimatorControllerParameterType.Trigger:
+                                        {
+                                            // Match the condition with an existing trigger
+                                            if (parameterName == parameter.name)
+                                            {
+                                                var transitionInfo = new TransitionStateinfo()
+                                                {
+                                                    Layer = x,
+                                                    OriginatingState = animatorState.nameHash,
+                                                    DestinationState = transition.destinationState.nameHash,
+                                                    TransitionDuration = transition.duration,
+                                                    TriggerNameHash = parameter.nameHash,
+                                                    TransitionIndex = z
+                                                };
+                                                TransitionStateInfoList.Add(transitionInfo);
+                                            }
+                                            break;
+                                        }
+                                    default:
+                                        break;
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+#endif
+        }
+
+        public void OnAfterDeserialize()
+        {
+            BuildDestinationToTransitionInfoTable();
+        }
+
+        public void OnBeforeSerialize()
+        {
+            BuildTransitionStateInfoList();
+        }
+
+        internal struct AnimationState : INetworkSerializable
+        {
+            // Not to be serialized, used for processing the animation state
+            internal bool HasBeenProcessed;
             internal int StateHash;
             internal float NormalizedTime;
             internal int Layer;
             internal float Weight;
 
+            // For synchronizing transitions
+            internal bool Transition;
+            // The StateHash is where the transition starts
+            // and the DestinationStateHash is the destination state
+            internal int DestinationStateHash;
+
             public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter
             {
-                serializer.SerializeValue(ref StateHash);
+                if (serializer.IsWriter)
-                serializer.SerializeValue(ref NormalizedTime);
+                {
-                serializer.SerializeValue(ref Layer);
+                    var writer = serializer.GetFastBufferWriter();
-                serializer.SerializeValue(ref Weight);
+                    var writeSize = FastBufferWriter.GetWriteSize(Transition);
+                    writeSize += FastBufferWriter.GetWriteSize(StateHash);
+                    writeSize += FastBufferWriter.GetWriteSize(NormalizedTime);
+                    writeSize += FastBufferWriter.GetWriteSize(Layer);
+                    writeSize += FastBufferWriter.GetWriteSize(Weight);
+                    if (Transition)
+                    {
+                        writeSize += FastBufferWriter.GetWriteSize(DestinationStateHash);
+                    }
+
+                    if (!writer.TryBeginWrite(writeSize))
+                    {
+                        throw new OverflowException($"[{GetType().Name}] Could not serialize: Out of buffer space.");
+                    }
+
+                    writer.WriteValue(Transition);
+                    writer.WriteValue(StateHash);
+                    writer.WriteValue(NormalizedTime);
+                    writer.WriteValue(Layer);
+                    writer.WriteValue(Weight);
+                    if (Transition)
+                    {
+                        writer.WriteValue(DestinationStateHash);
+                    }
+                }
+                else
+                {
+                    var reader = serializer.GetFastBufferReader();
+                    // Begin reading the Transition flag
+                    if (!reader.TryBeginRead(FastBufferWriter.GetWriteSize(Transition)))
+                    {
+                        throw new OverflowException($"[{GetType().Name}] Could not deserialize: Out of buffer space.");
+                    }
+                    reader.ReadValue(out Transition);
+
+                    // Now determine what remains to be read
+                    var readSize = FastBufferWriter.GetWriteSize(StateHash);
+                    readSize += FastBufferWriter.GetWriteSize(NormalizedTime);
+                    readSize += FastBufferWriter.GetWriteSize(Layer);
+                    readSize += FastBufferWriter.GetWriteSize(Weight);
+                    if (Transition)
+                    {
+                        readSize += FastBufferWriter.GetWriteSize(DestinationStateHash);
+                    }
+
+                    // Now read the remaining information about this AnimationState
+                    if (!reader.TryBeginRead(readSize))
+                    {
+                        throw new OverflowException($"[{GetType().Name}] Could not deserialize: Out of buffer space.");
+                    }
+
+                    reader.ReadValue(out StateHash);
+                    reader.ReadValue(out NormalizedTime);
+                    reader.ReadValue(out Layer);
+                    reader.ReadValue(out Weight);
+                    if (Transition)
+                    {
+                        reader.ReadValue(out DestinationStateHash);
+                    }
+                }
+            }
+        }
+
+        internal struct AnimationMessage : INetworkSerializable
+        {
+            // Not to be serialized, used for processing the animation message
+            internal bool HasBeenProcessed;
+
+            // This is preallocated/populated in OnNetworkSpawn for all instances in the event ownership or
+            // authority changes.  When serializing, IsDirtyCount determines how many AnimationState entries
+            // should be serialized from the list.  When deserializing the list is created and populated with
+            // only the number of AnimationStates received which is dictated by the deserialized IsDirtyCount.
+            internal List<AnimationState> AnimationStates;
+
+            // Used to determine how many AnimationState entries we are sending or receiving
+            internal int IsDirtyCount;
+
+            public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter
+            {
+                var animationState = new AnimationState();
+                if (serializer.IsReader)
+                {
+                    AnimationStates = new List<AnimationState>();
+
+                    serializer.SerializeValue(ref IsDirtyCount);
+                    // Since we create a new AnimationMessage when deserializing
+                    // we need to create new animation states for each incoming
+                    // AnimationState being updated
+                    for (int i = 0; i < IsDirtyCount; i++)
+                    {
+                        animationState = new AnimationState();
+                        serializer.SerializeValue(ref animationState);
+                        AnimationStates.Add(animationState);
+                    }
+                }
+                else
+                {
+                    // When writing, only send the counted dirty animation states
+                    serializer.SerializeValue(ref IsDirtyCount);
+                    for (int i = 0; i < IsDirtyCount; i++)
+                    {
+                        animationState = AnimationStates[i];
+                        serializer.SerializeNetworkSerializable(ref animationState);
+                    }
+                }
             }
         }
 
@@ -221,7 +480,8 @@ namespace Unity.Netcode.Components
             return true;
         }
 
-        // Animators only support up to 32 params
+        // Animators only support up to 32 parameters
+        // TODO: Look into making this a range limited property
         private const int k_MaxAnimationParams = 32;
 
         private int[] m_TransitionHash;
@@ -267,9 +527,9 @@ namespace Unity.Netcode.Components
                 m_NetworkAnimatorStateChangeHandler = null;
             }
 
-            if (IsServer)
+            if (m_CachedNetworkManager != null)
             {
-                NetworkManager.OnClientConnectedCallback -= OnClientConnectedCallback;
+                m_CachedNetworkManager.OnClientConnectedCallback -= OnClientConnectedCallback;
             }
 
             if (m_CachedAnimatorParameters != null && m_CachedAnimatorParameters.IsCreated)
@@ -291,40 +551,64 @@ namespace Unity.Netcode.Components
         private List<int> m_ParametersToUpdate;
         private List<ulong> m_ClientSendList;
         private ClientRpcParams m_ClientRpcParams;
+        private AnimationMessage m_AnimationMessage;
 
+        /// <summary>
+        /// Used for integration test to validate that the
+        /// AnimationMessage.AnimationStates remains the same
+        /// size as the layer count.
+        /// </summary>
+        internal AnimationMessage GetAnimationMessage()
+        {
+            return m_AnimationMessage;
+        }
+
+        // Only used in Cleanup
+        private NetworkManager m_CachedNetworkManager;
+
+        /// <inheritdoc/>
         public override void OnNetworkSpawn()
-        {
-            if (IsOwner || IsServer)
         {
             int layers = m_Animator.layerCount;
+
+            // Initializing the below arrays for everyone handles an issue
+            // when running in owner authoritative mode and the owner changes.
             m_TransitionHash = new int[layers];
             m_AnimationHash = new int[layers];
             m_LayerWeights = new float[layers];
 
-                if (IsServer)
-                {
-                    NetworkManager.OnClientConnectedCallback += OnClientConnectedCallback;
-                }
-
-                // Store off our current layer weights
-                for (int layer = 0; layer < m_Animator.layerCount; layer++)
-                {
-                    float layerWeightNow = m_Animator.GetLayerWeight(layer);
-                    if (layerWeightNow != m_LayerWeights[layer])
-                    {
-                        m_LayerWeights[layer] = layerWeightNow;
-                    }
-                }
-
             if (IsServer)
             {
                 m_ClientSendList = new List<ulong>(128);
                 m_ClientRpcParams = new ClientRpcParams();
                 m_ClientRpcParams.Send = new ClientRpcSendParams();
                 m_ClientRpcParams.Send.TargetClientIds = m_ClientSendList;
+
+                // Cache the NetworkManager instance to remove the OnClientConnectedCallback subscription
+                m_CachedNetworkManager = NetworkManager;
+                NetworkManager.OnClientConnectedCallback += OnClientConnectedCallback;
+            }
+            // We initialize the m_AnimationMessage for all instances in the event that
+            // ownership or authority changes during runtime.
+            m_AnimationMessage = new AnimationMessage();
+            m_AnimationMessage.AnimationStates = new List<AnimationState>();
+
+            // Store off our current layer weights and create our animation
+            // state entries per layer.
+            for (int layer = 0; layer < m_Animator.layerCount; layer++)
+            {
+                // We create an AnimationState per layer to preallocate the maximum
+                // number of possible AnimationState changes we could send in one
+                // AnimationMessage.
+                m_AnimationMessage.AnimationStates.Add(new AnimationState());
+                float layerWeightNow = m_Animator.GetLayerWeight(layer);
+                if (layerWeightNow != m_LayerWeights[layer])
+                {
+                    m_LayerWeights[layer] = layerWeightNow;
                 }
             }
 
+            // Build our reference parameter values to detect when they change
             var parameters = m_Animator.parameters;
             m_CachedAnimatorParameters = new NativeArray<AnimatorParamCache>(parameters.Length, Allocator.Persistent);
             m_ParametersToUpdate = new List<int>(parameters.Length);
@@ -371,6 +655,7 @@ namespace Unity.Netcode.Components
             m_NetworkAnimatorStateChangeHandler = new NetworkAnimatorStateChangeHandler(this);
         }
 
+        /// <inheritdoc/>
         public override void OnNetworkDespawn()
         {
             Cleanup();
@@ -391,18 +676,25 @@ namespace Unity.Netcode.Components
                 m_ParametersToUpdate.Add(i);
             }
             SendParametersUpdate(m_ClientRpcParams);
+
+            // Reset the dirty count before synchronizing the newly connected client with all layers
+            m_AnimationMessage.IsDirtyCount = 0;
+
             for (int layer = 0; layer < m_Animator.layerCount; layer++)
             {
                 AnimatorStateInfo st = m_Animator.GetCurrentAnimatorStateInfo(layer);
-
                 var stateHash = st.fullPathHash;
                 var normalizedTime = st.normalizedTime;
-                var totalSpeed = st.speed * st.speedMultiplier;
+                var isInTransition = m_Animator.IsInTransition(layer);
-                var adjustedNormalizedMaxTime = totalSpeed > 0.0f ? 1.0f / totalSpeed : 0.0f;
+
-                // NOTE:
+                // Grab one of the available AnimationState entries so we can fill it with the current
-                // When synchronizing, for now we will just complete the transition and
+                // layer's animation state.
-                // synchronize the player to the next state being transitioned into
+                var animationState = m_AnimationMessage.AnimationStates[layer];
-                if (m_Animator.IsInTransition(layer))
+
+                // Synchronizing transitions with trigger conditions for late joining clients is now
+                // handled by cross fading between the late joining client's current layer's AnimationState
+                // and the transition's destination AnimationState.
+                if (isInTransition)
                 {
                     var tt = m_Animator.GetAnimatorTransitionInfo(layer);
                     var nextState = m_Animator.GetNextAnimatorStateInfo(layer);
@@ -420,32 +712,47 @@ namespace Unity.Netcode.Components
                     {
                         normalizedTime = 0.0f;
                     }
-
                     stateHash = nextState.fullPathHash;
-                }
-                else
-                if (st.normalizedTime >= adjustedNormalizedMaxTime)
-                {
-                    continue;
-                }
 
-                var animMsg = new AnimationMessage
+                    // Use the destination state to transition info lookup table to see if this is a transition we can
+                    // synchronize using cross fading
+                    if (m_DestinationStateToTransitioninfo.ContainsKey(layer))
                     {
-                    StateHash = stateHash,
+                        if (m_DestinationStateToTransitioninfo[layer].ContainsKey(nextState.shortNameHash))
-                    NormalizedTime = normalizedTime,
+                        {
-                    Layer = layer,
+                            var destinationInfo = m_DestinationStateToTransitioninfo[layer][nextState.shortNameHash];
-                    Weight = m_LayerWeights[layer]
+                            stateHash = destinationInfo.OriginatingState;
-                };
+                            // Set the destination state to cross fade to from the originating state
-                // Server always send via client RPC
+                            animationState.DestinationStateHash = destinationInfo.DestinationState;
-                SendAnimStateClientRpc(animMsg, m_ClientRpcParams);
+                        }
                     }
                 }
 
+                animationState.Transition = isInTransition;        // The only time this could be set to true
+                animationState.StateHash = stateHash;              // When a transition, this is the originating/starting state
+                animationState.NormalizedTime = normalizedTime;
+                animationState.Layer = layer;
+                animationState.Weight = m_LayerWeights[layer];
+
+                // Apply the changes
+                m_AnimationMessage.AnimationStates[layer] = animationState;
+            }
+            // Send all animation states
+            m_AnimationMessage.IsDirtyCount = m_Animator.layerCount;
+            SendAnimStateClientRpc(m_AnimationMessage, m_ClientRpcParams);
+        }
+
+        /// <summary>
+        /// Required for the server to synchronize newly joining players
+        /// </summary>
         private void OnClientConnectedCallback(ulong playerId)
         {
             m_NetworkAnimatorStateChangeHandler.SynchronizeClient(playerId);
         }
 
+        /// <summary>
+        /// Checks for changes in both Animator parameters and state.
+        /// </summary>
         internal void CheckForAnimatorChanges()
         {
             if (!IsOwner && !IsServerAuthoritative() || IsServerAuthoritative() && !IsServer)
@@ -460,45 +767,57 @@ namespace Unity.Netcode.Components
 
             if (m_Animator.runtimeAnimatorController == null)
             {
+                if (NetworkManager.LogLevel == LogLevel.Developer)
+                {
+                    Debug.LogError($"[{GetType().Name}] Could not find an assigned {nameof(RuntimeAnimatorController)}! Cannot check {nameof(Animator)} for changes in state!");
+                }
                 return;
             }
 
             int stateHash;
             float normalizedTime;
 
-            // This sends updates only if a layer change or transition is happening
+            // Reset the dirty count before checking for AnimationState updates
+            m_AnimationMessage.IsDirtyCount = 0;
+
+            // This sends updates only if a layer's state has changed
             for (int layer = 0; layer < m_Animator.layerCount; layer++)
             {
                 AnimatorStateInfo st = m_Animator.GetCurrentAnimatorStateInfo(layer);
                 var totalSpeed = st.speed * st.speedMultiplier;
                 var adjustedNormalizedMaxTime = totalSpeed > 0.0f ? 1.0f / totalSpeed : 0.0f;
 
-                // determine if we have reached the end of our state time, if so we can skip
-                if (st.normalizedTime >= adjustedNormalizedMaxTime)
-                {
-                    continue;
-                }
-
                 if (!CheckAnimStateChanged(out stateHash, out normalizedTime, layer))
                 {
                     continue;
                 }
 
-                var animMsg = new AnimationMessage
+                // If we made it here, then we need to synchronize this layer's animation state.
-                {
+                // Get one of the preallocated AnimationState entries and populate it with the
-                    StateHash = stateHash,
+                // current layer's state.
-                    NormalizedTime = normalizedTime,
+                var animationState = m_AnimationMessage.AnimationStates[m_AnimationMessage.IsDirtyCount];
-                    Layer = layer,
-                    Weight = m_LayerWeights[layer]
-                };
 
+                animationState.Transition = false; // Only used during synchronization
+                animationState.StateHash = stateHash;
+                animationState.NormalizedTime = normalizedTime;
+                animationState.Layer = layer;
+                animationState.Weight = m_LayerWeights[layer];
+
+                // Apply the changes
+                m_AnimationMessage.AnimationStates[m_AnimationMessage.IsDirtyCount] = animationState;
+                m_AnimationMessage.IsDirtyCount++;
+            }
+
+            // Send an AnimationMessage only if there are dirty AnimationStates to send
+            if (m_AnimationMessage.IsDirtyCount > 0)
+            {
                 if (!IsServer && IsOwner)
                 {
-                    SendAnimStateServerRpc(animMsg);
+                    SendAnimStateServerRpc(m_AnimationMessage);
                 }
                 else
                 {
-                    SendAnimStateClientRpc(animMsg);
+                    SendAnimStateClientRpc(m_AnimationMessage);
                 }
             }
         }
@@ -594,7 +913,7 @@ namespace Unity.Netcode.Components
         /// <summary>
         /// Checks if any of the Animator's states have changed
         /// </summary>
-        private unsafe bool CheckAnimStateChanged(out int stateHash, out float normalizedTime, int layer)
+        private bool CheckAnimStateChanged(out int stateHash, out float normalizedTime, int layer)
         {
             stateHash = 0;
             normalizedTime = 0;
@@ -744,14 +1063,57 @@ namespace Unity.Netcode.Components
         }
 
         /// <summary>
-        /// Applies the AnimationMessage state to the Animator
+        /// Applies the AnimationState state to the Animator
         /// </summary>
-        private unsafe void UpdateAnimationState(AnimationMessage animationState)
+        internal void UpdateAnimationState(AnimationState animationState)
         {
-            if (animationState.StateHash != 0)
+            if (animationState.StateHash == 0)
+            {
+                return;
+            }
+
+            var currentState = m_Animator.GetCurrentAnimatorStateInfo(animationState.Layer);
+            // If it is a transition, then we are synchronizing transitions in progress when a client late joins
+            if (animationState.Transition)
+            {
+                // We should have all valid entries for any animation state transition update
+                // Verify the AnimationState's assigned Layer exists
+                if (m_DestinationStateToTransitioninfo.ContainsKey(animationState.Layer))
+                {
+                    // Verify the inner-table has the destination AnimationState name hash
+                    if (m_DestinationStateToTransitioninfo[animationState.Layer].ContainsKey(animationState.DestinationStateHash))
+                    {
+                        // Make sure we are on the originating/starting state we are going to cross fade into
+                        if (currentState.shortNameHash == animationState.StateHash)
+                        {
+                            // Get the transition state information
+                            var transitionStateInfo = m_DestinationStateToTransitioninfo[animationState.Layer][animationState.DestinationStateHash];
+
+                            // Cross fade from the current to the destination state for the transitions duration while starting at the server's current normalized time of the transition
+                            m_Animator.CrossFade(transitionStateInfo.DestinationState, transitionStateInfo.TransitionDuration, transitionStateInfo.Layer, 0.0f, animationState.NormalizedTime);
+                        }
+                        else if (NetworkManager.LogLevel == LogLevel.Developer)
+                        {
+                            NetworkLog.LogWarning($"Current State Hash ({currentState.fullPathHash}) != AnimationState.StateHash ({animationState.StateHash})");
+                        }
+                    }
+                    else if (NetworkManager.LogLevel == LogLevel.Developer)
+                    {
+                        NetworkLog.LogError($"[DestinationState To Transition Info] Layer ({animationState.Layer}) sub-table does not contain destination state ({animationState.DestinationStateHash})!");
+                    }
+                }
+                else if (NetworkManager.LogLevel == LogLevel.Developer)
+                {
+                    NetworkLog.LogError($"[DestinationState To Transition Info] Layer ({animationState.Layer}) does not exist!");
+                }
+            }
+            else
+            {
+                if (currentState.fullPathHash != animationState.StateHash)
                 {
                     m_Animator.Play(animationState.StateHash, animationState.Layer, animationState.NormalizedTime);
                 }
+            }
             m_Animator.SetLayerWeight(animationState.Layer, animationState.Weight);
         }
 
@@ -773,7 +1135,7 @@ namespace Unity.Netcode.Components
                     return;
                 }
                 UpdateParameters(parametersUpdate);
-                if (NetworkManager.ConnectedClientsIds.Count - 2 > 0)
+                if (NetworkManager.ConnectedClientsIds.Count > (IsHost ? 2 : 1))
                 {
                     m_ClientSendList.Clear();
                     m_ClientSendList.AddRange(NetworkManager.ConnectedClientsIds);
@@ -803,11 +1165,11 @@ namespace Unity.Netcode.Components
         /// The server sets its local state and then forwards the message to the remaining clients
         /// </summary>
         [ServerRpc]
-        private unsafe void SendAnimStateServerRpc(AnimationMessage animSnapshot, ServerRpcParams serverRpcParams = default)
+        private unsafe void SendAnimStateServerRpc(AnimationMessage animationMessage, ServerRpcParams serverRpcParams = default)
         {
             if (IsServerAuthoritative())
             {
-                m_NetworkAnimatorStateChangeHandler.SendAnimationUpdate(animSnapshot);
+                m_NetworkAnimatorStateChangeHandler.SendAnimationUpdate(animationMessage);
             }
             else
             {
@@ -815,15 +1177,21 @@ namespace Unity.Netcode.Components
                 {
                     return;
                 }
-                UpdateAnimationState(animSnapshot);
+
-                if (NetworkManager.ConnectedClientsIds.Count - 2 > 0)
+                foreach (var animationState in animationMessage.AnimationStates)
+                {
+                    UpdateAnimationState(animationState);
+                }
+
+                m_NetworkAnimatorStateChangeHandler.AddAnimationMessageToProcessQueue(animationMessage);
+                if (NetworkManager.ConnectedClientsIds.Count > (IsHost ? 2 : 1))
                 {
                     m_ClientSendList.Clear();
                     m_ClientSendList.AddRange(NetworkManager.ConnectedClientsIds);
                     m_ClientSendList.Remove(serverRpcParams.Receive.SenderClientId);
                     m_ClientSendList.Remove(NetworkManager.ServerClientId);
                     m_ClientRpcParams.Send.TargetClientIds = m_ClientSendList;
-                    m_NetworkAnimatorStateChangeHandler.SendAnimationUpdate(animSnapshot, m_ClientRpcParams);
+                    m_NetworkAnimatorStateChangeHandler.SendAnimationUpdate(animationMessage, m_ClientRpcParams);
                 }
             }
         }
@@ -832,12 +1200,25 @@ namespace Unity.Netcode.Components
         /// Internally-called RPC client receiving function to update some animation state on a client
         /// </summary>
         [ClientRpc]
-        private unsafe void SendAnimStateClientRpc(AnimationMessage animSnapshot, ClientRpcParams clientRpcParams = default)
+        private unsafe void SendAnimStateClientRpc(AnimationMessage animationMessage, ClientRpcParams clientRpcParams = default)
         {
+            // This should never happen
+            if (IsHost)
+            {
+                if (NetworkManager.LogLevel == LogLevel.Developer)
+                {
+                    NetworkLog.LogWarning("Detected the Host is sending itself animation updates! Please report this issue.");
+                }
+                return;
+            }
+
             var isServerAuthoritative = IsServerAuthoritative();
             if (!isServerAuthoritative && !IsOwner || isServerAuthoritative)
             {
-                UpdateAnimationState(animSnapshot);
+                foreach (var animationState in animationMessage.AnimationStates)
+                {
+                    UpdateAnimationState(animationState);
+                }
             }
         }
 
@@ -846,48 +1227,67 @@ namespace Unity.Netcode.Components
         /// The server sets its local state and then forwards the message to the remaining clients
         /// </summary>
         [ServerRpc]
-        private void SendAnimTriggerServerRpc(AnimationTriggerMessage animationTriggerMessage, ServerRpcParams serverRpcParams = default)
+        internal void SendAnimTriggerServerRpc(AnimationTriggerMessage animationTriggerMessage, ServerRpcParams serverRpcParams = default)
         {
+            // If it is server authoritative
             if (IsServerAuthoritative())
             {
-                m_NetworkAnimatorStateChangeHandler.SendTriggerUpdate(animationTriggerMessage);
+                // The only condition where this should (be allowed to) happen is when the owner sends the server a trigger message
+                if (OwnerClientId == serverRpcParams.Receive.SenderClientId)
+                {
+                    m_NetworkAnimatorStateChangeHandler.QueueTriggerUpdateToClient(animationTriggerMessage);
+                }
+                else if (NetworkManager.LogLevel == LogLevel.Developer)
+                {
+                    NetworkLog.LogWarning($"[Server Authoritative] Detected the a non-authoritative client is sending the server animation trigger updates. If you recently changed ownership of the {name} object, then this could be the reason.");
+                }
             }
             else
             {
+                // Ignore if a non-owner sent this.
                 if (serverRpcParams.Receive.SenderClientId != OwnerClientId)
                 {
+                    if (NetworkManager.LogLevel == LogLevel.Developer)
+                    {
+                        NetworkLog.LogWarning($"[Owner Authoritative] Detected the a non-authoritative client is sending the server animation trigger updates. If you recently changed ownership of the {name} object, then this could be the reason.");
+                    }
                     return;
                 }
-                //  trigger the animation locally on the server...
-                m_Animator.SetBool(animationTriggerMessage.Hash, animationTriggerMessage.IsTriggerSet);
 
-                if (NetworkManager.ConnectedClientsIds.Count - 2 > 0)
+                // set the trigger locally on the server
+                InternalSetTrigger(animationTriggerMessage.Hash, animationTriggerMessage.IsTriggerSet);
+
+                // send the message to all non-authority clients excluding the server and the owner
+                if (NetworkManager.ConnectedClientsIds.Count > (IsHost ? 2 : 1))
                 {
                     m_ClientSendList.Clear();
                     m_ClientSendList.AddRange(NetworkManager.ConnectedClientsIds);
                     m_ClientSendList.Remove(serverRpcParams.Receive.SenderClientId);
                     m_ClientSendList.Remove(NetworkManager.ServerClientId);
                     m_ClientRpcParams.Send.TargetClientIds = m_ClientSendList;
-                    m_NetworkAnimatorStateChangeHandler.SendTriggerUpdate(animationTriggerMessage, m_ClientRpcParams);
+                    m_NetworkAnimatorStateChangeHandler.QueueTriggerUpdateToClient(animationTriggerMessage, m_ClientRpcParams);
+                }
             }
         }
 
+        /// <summary>
+        /// See above <see cref="m_LastTriggerHash"/>
+        /// </summary>
+        private void InternalSetTrigger(int hash, bool isSet = true)
+        {
+            m_Animator.SetBool(hash, isSet);
         }
 
         /// <summary>
         /// Internally-called RPC client receiving function to update a trigger when the server wants to forward
         ///   a trigger for a client to play / reset
         /// </summary>
-        /// <param name="animSnapshot">the payload containing the trigger data to apply</param>
+        /// <param name="animationTriggerMessage">the payload containing the trigger data to apply</param>
         /// <param name="clientRpcParams">unused</param>
         [ClientRpc]
         internal void SendAnimTriggerClientRpc(AnimationTriggerMessage animationTriggerMessage, ClientRpcParams clientRpcParams = default)
         {
-            var isServerAuthoritative = IsServerAuthoritative();
+            InternalSetTrigger(animationTriggerMessage.Hash, animationTriggerMessage.IsTriggerSet);
-            if (!isServerAuthoritative && !IsOwner || isServerAuthoritative)
-            {
-                m_Animator.SetBool(animationTriggerMessage.Hash, animationTriggerMessage.IsTriggerSet);
-            }
         }
 
         /// <summary>
@@ -904,20 +1304,33 @@ namespace Unity.Netcode.Components
         /// <param name="setTrigger">sets (true) or resets (false) the trigger. The default is to set it (true).</param>
         public void SetTrigger(int hash, bool setTrigger = true)
         {
-            var isServerAuthoritative = IsServerAuthoritative();
+            // MTT-3564:
-            if (IsOwner && !isServerAuthoritative || IsServer && isServerAuthoritative)
+            // After fixing the issue with trigger controlled Transitions being synchronized twice,
+            // it exposed additional issues with this logic.  Now, either the owner or the server can
+            // update triggers. Since server-side RPCs are immediately invoked, for a host a trigger
+            // will happen when SendAnimTriggerClientRpc is called.  For a client owner, we call the
+            // SendAnimTriggerServerRpc and then trigger locally when running in owner authority mode.
+            if (IsOwner || IsServer)
             {
                 var animTriggerMessage = new AnimationTriggerMessage() { Hash = hash, IsTriggerSet = setTrigger };
                 if (IsServer)
                 {
-                    SendAnimTriggerClientRpc(animTriggerMessage);
+                    /// <see cref="UpdatePendingTriggerStates"/> as to why we queue
+                    m_NetworkAnimatorStateChangeHandler.QueueTriggerUpdateToClient(animTriggerMessage);
+                    if (!IsHost)
+                    {
+                        InternalSetTrigger(hash);
+                    }
                 }
                 else
                 {
-                    SendAnimTriggerServerRpc(animTriggerMessage);
+                    /// <see cref="UpdatePendingTriggerStates"/> as to why we queue
+                    m_NetworkAnimatorStateChangeHandler.QueueTriggerUpdateToServer(animTriggerMessage);
+                    if (!IsServerAuthoritative())
+                    {
+                        InternalSetTrigger(hash);
+                    }
                 }
-                //  trigger the animation locally on the server...
-                m_Animator.SetBool(hash, setTrigger);
             }
         }
 

Components/NetworkRigidbody.cs

@@ -9,6 +9,7 @@ namespace Unity.Netcode.Components
     /// </summary>
     [RequireComponent(typeof(Rigidbody))]
     [RequireComponent(typeof(NetworkTransform))]
+    [AddComponentMenu("Netcode/Network Rigidbody")]
     public class NetworkRigidbody : NetworkBehaviour
     {
         /// <summary>

Components/NetworkRigidbody2D.cs

@@ -9,6 +9,7 @@ namespace Unity.Netcode.Components
     /// </summary>
     [RequireComponent(typeof(Rigidbody2D))]
     [RequireComponent(typeof(NetworkTransform))]
+    [AddComponentMenu("Netcode/Network Rigidbody 2D")]
     public class NetworkRigidbody2D : NetworkBehaviour
     {
         private Rigidbody2D m_Rigidbody;

Editor/CodeGen/CodeGenHelpers.cs

@@ -15,6 +15,10 @@ namespace Unity.Netcode.Editor.CodeGen
 {
     internal static class CodeGenHelpers
     {
+        public const string DotnetModuleName = "netstandard.dll";
+        public const string UnityModuleName = "UnityEngine.CoreModule.dll";
+        public const string NetcodeModuleName = "Unity.Netcode.Runtime.dll";
+
         public const string RuntimeAssemblyName = "Unity.Netcode.Runtime";
 
         public static readonly string NetworkBehaviour_FullName = typeof(NetworkBehaviour).FullName;
@@ -119,6 +123,19 @@ namespace Unity.Netcode.Editor.CodeGen
             try
             {
                 var typeDef = typeReference.Resolve();
+                // Note: this won't catch generics correctly.
+                //
+                //     class Foo<T>: IInterface<T> {}
+                //     class Bar: Foo<int> {}
+                //
+                // Bar.HasInterface(IInterface<int>) -> returns false even though it should be true.
+                //
+                // This can be fixed (see GetAllFieldsAndResolveGenerics() in NetworkBehaviourILPP to understand how)
+                // but right now we don't need that to work so it's left alone to reduce complexity
+                if (typeDef.BaseType.HasInterface(interfaceTypeFullName))
+                {
+                    return true;
+                }
                 var typeFaces = typeDef.Interfaces;
                 return typeFaces.Any(iface => iface.InterfaceType.FullName == interfaceTypeFullName);
             }
@@ -380,5 +397,74 @@ namespace Unity.Netcode.Editor.CodeGen
 
             return assemblyDefinition;
         }
+
+        private static void SearchForBaseModulesRecursive(AssemblyDefinition assemblyDefinition, PostProcessorAssemblyResolver assemblyResolver, ref ModuleDefinition unityModule, ref ModuleDefinition netcodeModule, HashSet<string> visited)
+        {
+
+            foreach (var module in assemblyDefinition.Modules)
+            {
+                if (module == null)
+                {
+                    continue;
+                }
+
+                if (unityModule != null && netcodeModule != null)
+                {
+                    return;
+                }
+
+                if (unityModule == null && module.Name == UnityModuleName)
+                {
+                    unityModule = module;
+                    continue;
+                }
+
+                if (netcodeModule == null && module.Name == NetcodeModuleName)
+                {
+                    netcodeModule = module;
+                    continue;
+                }
+            }
+            if (unityModule != null && netcodeModule != null)
+            {
+                return;
+            }
+
+            foreach (var assemblyNameReference in assemblyDefinition.MainModule.AssemblyReferences)
+            {
+                if (assemblyNameReference == null)
+                {
+                    continue;
+                }
+                if (visited.Contains(assemblyNameReference.Name))
+                {
+                    continue;
+                }
+
+                visited.Add(assemblyNameReference.Name);
+
+                var assembly = assemblyResolver.Resolve(assemblyNameReference);
+                if (assembly == null)
+                {
+                    continue;
+                }
+                SearchForBaseModulesRecursive(assembly, assemblyResolver, ref unityModule, ref netcodeModule, visited);
+
+                if (unityModule != null && netcodeModule != null)
+                {
+                    return;
+                }
+            }
+        }
+
+        public static (ModuleDefinition UnityModule, ModuleDefinition NetcodeModule) FindBaseModules(AssemblyDefinition assemblyDefinition, PostProcessorAssemblyResolver assemblyResolver)
+        {
+            ModuleDefinition unityModule = null;
+            ModuleDefinition netcodeModule = null;
+            var visited = new HashSet<string>();
+            SearchForBaseModulesRecursive(assemblyDefinition, assemblyResolver, ref unityModule, ref netcodeModule, visited);
+
+            return (unityModule, netcodeModule);
+        }
     }
 }

Editor/CodeGen/INetworkMessageILPP.cs

@@ -2,7 +2,6 @@ using System;
 using System.IO;
 using System.Linq;
 using System.Collections.Generic;
-using System.Reflection;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
 using Mono.Cecil.Rocks;
@@ -17,9 +16,7 @@ namespace Unity.Netcode.Editor.CodeGen
     {
         public override ILPPInterface GetInstance() => this;
 
-        public override bool WillProcess(ICompiledAssembly compiledAssembly) =>
+        public override bool WillProcess(ICompiledAssembly compiledAssembly) => compiledAssembly.Name == CodeGenHelpers.RuntimeAssemblyName;
-            compiledAssembly.Name == CodeGenHelpers.RuntimeAssemblyName ||
-            compiledAssembly.References.Any(filePath => Path.GetFileNameWithoutExtension(filePath) == CodeGenHelpers.RuntimeAssemblyName);
 
         private readonly List<DiagnosticMessage> m_Diagnostics = new List<DiagnosticMessage>();
 
@@ -33,13 +30,22 @@ namespace Unity.Netcode.Editor.CodeGen
             m_Diagnostics.Clear();
 
             // read
-            var assemblyDefinition = CodeGenHelpers.AssemblyDefinitionFor(compiledAssembly, out var resolver);
+            var assemblyDefinition = CodeGenHelpers.AssemblyDefinitionFor(compiledAssembly, out m_AssemblyResolver);
             if (assemblyDefinition == null)
             {
                 m_Diagnostics.AddError($"Cannot read assembly definition: {compiledAssembly.Name}");
                 return null;
             }
 
+            // modules
+            (_, m_NetcodeModule) = CodeGenHelpers.FindBaseModules(assemblyDefinition, m_AssemblyResolver);
+
+            if (m_NetcodeModule == null)
+            {
+                m_Diagnostics.AddError($"Cannot find Netcode module: {CodeGenHelpers.NetcodeModuleName}");
+                return null;
+            }
+
             // process
             var mainModule = assemblyDefinition.MainModule;
             if (mainModule != null)
@@ -61,7 +67,7 @@ namespace Unity.Netcode.Editor.CodeGen
                     }
                     catch (Exception e)
                     {
-                        m_Diagnostics.AddError((e.ToString() + e.StackTrace.ToString()).Replace("\n", "|").Replace("\r", "|"));
+                        m_Diagnostics.AddError((e.ToString() + e.StackTrace).Replace("\n", "|").Replace("\r", "|"));
                     }
                 }
                 else
@@ -92,77 +98,136 @@ namespace Unity.Netcode.Editor.CodeGen
             return new ILPostProcessResult(new InMemoryAssembly(pe.ToArray(), pdb.ToArray()), m_Diagnostics);
         }
 
+        private ModuleDefinition m_NetcodeModule;
+        private PostProcessorAssemblyResolver m_AssemblyResolver;
 
         private MethodReference m_MessagingSystem_ReceiveMessage_MethodRef;
+        private MethodReference m_MessagingSystem_CreateMessageAndGetVersion_MethodRef;
         private TypeReference m_MessagingSystem_MessageWithHandler_TypeRef;
         private MethodReference m_MessagingSystem_MessageHandler_Constructor_TypeRef;
+        private MethodReference m_MessagingSystem_VersionGetter_Constructor_TypeRef;
         private FieldReference m_ILPPMessageProvider___network_message_types_FieldRef;
         private FieldReference m_MessagingSystem_MessageWithHandler_MessageType_FieldRef;
         private FieldReference m_MessagingSystem_MessageWithHandler_Handler_FieldRef;
+        private FieldReference m_MessagingSystem_MessageWithHandler_GetVersion_FieldRef;
         private MethodReference m_Type_GetTypeFromHandle_MethodRef;
         private MethodReference m_List_Add_MethodRef;
 
         private const string k_ReceiveMessageName = nameof(MessagingSystem.ReceiveMessage);
+        private const string k_CreateMessageAndGetVersionName = nameof(MessagingSystem.CreateMessageAndGetVersion);
 
         private bool ImportReferences(ModuleDefinition moduleDefinition)
         {
-            m_MessagingSystem_MessageHandler_Constructor_TypeRef = moduleDefinition.ImportReference(typeof(MessagingSystem.MessageHandler).GetConstructors()[0]);
+            // Different environments seem to have different situations...
+            // Some have these definitions in netstandard.dll...
+            // some seem to have them elsewhere...
+            // Since they're standard .net classes they're not going to cause
+            // the same issues as referencing other assemblies, in theory, since
+            // the definitions should be standard and consistent across platforms
+            // (i.e., there's no #if UNITY_EDITOR in them that could create
+            // invalid IL code)
+            TypeDefinition typeTypeDef = moduleDefinition.ImportReference(typeof(Type)).Resolve();
+            TypeDefinition listTypeDef = moduleDefinition.ImportReference(typeof(List<>)).Resolve();
 
-            var messageWithHandlerType = typeof(MessagingSystem.MessageWithHandler);
+            TypeDefinition messageHandlerTypeDef = null;
-            m_MessagingSystem_MessageWithHandler_TypeRef = moduleDefinition.ImportReference(messageWithHandlerType);
+            TypeDefinition versionGetterTypeDef = null;
-            foreach (var fieldInfo in messageWithHandlerType.GetFields())
+            TypeDefinition messageWithHandlerTypeDef = null;
+            TypeDefinition ilppMessageProviderTypeDef = null;
+            TypeDefinition messagingSystemTypeDef = null;
+            foreach (var netcodeTypeDef in m_NetcodeModule.GetAllTypes())
             {
-                switch (fieldInfo.Name)
+                if (messageHandlerTypeDef == null && netcodeTypeDef.Name == nameof(MessagingSystem.MessageHandler))
+                {
+                    messageHandlerTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (versionGetterTypeDef == null && netcodeTypeDef.Name == nameof(MessagingSystem.VersionGetter))
+                {
+                    versionGetterTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (messageWithHandlerTypeDef == null && netcodeTypeDef.Name == nameof(MessagingSystem.MessageWithHandler))
+                {
+                    messageWithHandlerTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (ilppMessageProviderTypeDef == null && netcodeTypeDef.Name == nameof(ILPPMessageProvider))
+                {
+                    ilppMessageProviderTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (messagingSystemTypeDef == null && netcodeTypeDef.Name == nameof(MessagingSystem))
+                {
+                    messagingSystemTypeDef = netcodeTypeDef;
+                    continue;
+                }
+            }
+
+            m_MessagingSystem_MessageHandler_Constructor_TypeRef = moduleDefinition.ImportReference(messageHandlerTypeDef.GetConstructors().First());
+            m_MessagingSystem_VersionGetter_Constructor_TypeRef = moduleDefinition.ImportReference(versionGetterTypeDef.GetConstructors().First());
+
+            m_MessagingSystem_MessageWithHandler_TypeRef = moduleDefinition.ImportReference(messageWithHandlerTypeDef);
+            foreach (var fieldDef in messageWithHandlerTypeDef.Fields)
+            {
+                switch (fieldDef.Name)
                 {
                     case nameof(MessagingSystem.MessageWithHandler.MessageType):
-                        m_MessagingSystem_MessageWithHandler_MessageType_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_MessagingSystem_MessageWithHandler_MessageType_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                     case nameof(MessagingSystem.MessageWithHandler.Handler):
-                        m_MessagingSystem_MessageWithHandler_Handler_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_MessagingSystem_MessageWithHandler_Handler_FieldRef = moduleDefinition.ImportReference(fieldDef);
+                        break;
+                    case nameof(MessagingSystem.MessageWithHandler.GetVersion):
+                        m_MessagingSystem_MessageWithHandler_GetVersion_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                 }
             }
 
-            var typeType = typeof(Type);
+            foreach (var methodDef in typeTypeDef.Methods)
-            foreach (var methodInfo in typeType.GetMethods())
             {
-                switch (methodInfo.Name)
+                switch (methodDef.Name)
                 {
                     case nameof(Type.GetTypeFromHandle):
-                        m_Type_GetTypeFromHandle_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_Type_GetTypeFromHandle_MethodRef = moduleDefinition.ImportReference(methodDef);
                         break;
                 }
             }
 
-            var ilppMessageProviderType = typeof(ILPPMessageProvider);
+            foreach (var fieldDef in ilppMessageProviderTypeDef.Fields)
-            foreach (var fieldInfo in ilppMessageProviderType.GetFields(BindingFlags.Static | BindingFlags.NonPublic))
             {
-                switch (fieldInfo.Name)
+                switch (fieldDef.Name)
                 {
                     case nameof(ILPPMessageProvider.__network_message_types):
-                        m_ILPPMessageProvider___network_message_types_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_ILPPMessageProvider___network_message_types_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                 }
             }
 
-            var listType = typeof(List<MessagingSystem.MessageWithHandler>);
+            foreach (var methodDef in listTypeDef.Methods)
-            foreach (var methodInfo in listType.GetMethods())
             {
-                switch (methodInfo.Name)
+                switch (methodDef.Name)
                 {
-                    case nameof(List<MessagingSystem.MessageWithHandler>.Add):
+                    case "Add":
-                        m_List_Add_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_List_Add_MethodRef = methodDef;
+                        m_List_Add_MethodRef.DeclaringType = listTypeDef.MakeGenericInstanceType(messageWithHandlerTypeDef);
+                        m_List_Add_MethodRef = moduleDefinition.ImportReference(m_List_Add_MethodRef);
                         break;
                 }
             }
 
-            var messagingSystemType = typeof(MessagingSystem);
+            foreach (var methodDef in messagingSystemTypeDef.Methods)
-            foreach (var methodInfo in messagingSystemType.GetMethods(BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public))
             {
-                switch (methodInfo.Name)
+                switch (methodDef.Name)
                 {
                     case k_ReceiveMessageName:
-                        m_MessagingSystem_ReceiveMessage_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_MessagingSystem_ReceiveMessage_MethodRef = moduleDefinition.ImportReference(methodDef);
+                        break;
+                    case k_CreateMessageAndGetVersionName:
+                        m_MessagingSystem_CreateMessageAndGetVersion_MethodRef = moduleDefinition.ImportReference(methodDef);
                         break;
                 }
             }
@@ -189,7 +254,7 @@ namespace Unity.Netcode.Editor.CodeGen
             return staticCtorMethodDef;
         }
 
-        private void CreateInstructionsToRegisterType(ILProcessor processor, List<Instruction> instructions, TypeReference type, MethodReference receiveMethod)
+        private void CreateInstructionsToRegisterType(ILProcessor processor, List<Instruction> instructions, TypeReference type, MethodReference receiveMethod, MethodReference versionMethod)
         {
             // MessagingSystem.__network_message_types.Add(new MessagingSystem.MessageWithHandler{MessageType=typeof(type), Handler=type.Receive});
             processor.Body.Variables.Add(new VariableDefinition(m_MessagingSystem_MessageWithHandler_TypeRef));
@@ -205,7 +270,7 @@ namespace Unity.Netcode.Editor.CodeGen
             instructions.Add(processor.Create(OpCodes.Call, m_Type_GetTypeFromHandle_MethodRef));
             instructions.Add(processor.Create(OpCodes.Stfld, m_MessagingSystem_MessageWithHandler_MessageType_FieldRef));
 
-            // tmp.Handler = type.Receive
+            // tmp.Handler = MessageHandler.ReceveMessage<type>
             instructions.Add(processor.Create(OpCodes.Ldloca, messageWithHandlerLocIdx));
             instructions.Add(processor.Create(OpCodes.Ldnull));
 
@@ -213,15 +278,22 @@ namespace Unity.Netcode.Editor.CodeGen
             instructions.Add(processor.Create(OpCodes.Newobj, m_MessagingSystem_MessageHandler_Constructor_TypeRef));
             instructions.Add(processor.Create(OpCodes.Stfld, m_MessagingSystem_MessageWithHandler_Handler_FieldRef));
 
+
+            // tmp.GetVersion = MessageHandler.CreateMessageAndGetVersion<type>
+            instructions.Add(processor.Create(OpCodes.Ldloca, messageWithHandlerLocIdx));
+            instructions.Add(processor.Create(OpCodes.Ldnull));
+
+            instructions.Add(processor.Create(OpCodes.Ldftn, versionMethod));
+            instructions.Add(processor.Create(OpCodes.Newobj, m_MessagingSystem_VersionGetter_Constructor_TypeRef));
+            instructions.Add(processor.Create(OpCodes.Stfld, m_MessagingSystem_MessageWithHandler_GetVersion_FieldRef));
+
             // ILPPMessageProvider.__network_message_types.Add(tmp);
             instructions.Add(processor.Create(OpCodes.Ldloc, messageWithHandlerLocIdx));
             instructions.Add(processor.Create(OpCodes.Callvirt, m_List_Add_MethodRef));
         }
 
-        // Creates a static module constructor (which is executed when the module is loaded) that registers all the
+        // Creates a static module constructor (which is executed when the module is loaded) that registers all the message types in the assembly with MessagingSystem.
-        // message types in the assembly with MessagingSystem.
+        // This is the same behavior as annotating a static method with [ModuleInitializer] in standardized C# (that attribute doesn't exist in Unity, but the static module constructor still works).
-        // This is the same behavior as annotating a static method with [ModuleInitializer] in standardized
-        // C# (that attribute doesn't exist in Unity, but the static module constructor still works)
         // https://docs.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.moduleinitializerattribute?view=net-5.0
         // https://web.archive.org/web/20100212140402/http://blogs.msdn.com/junfeng/archive/2005/11/19/494914.aspx
         private void CreateModuleInitializer(AssemblyDefinition assembly, List<TypeDefinition> networkMessageTypes)
@@ -240,7 +312,9 @@ namespace Unity.Netcode.Editor.CodeGen
                     {
                         var receiveMethod = new GenericInstanceMethod(m_MessagingSystem_ReceiveMessage_MethodRef);
                         receiveMethod.GenericArguments.Add(type);
-                        CreateInstructionsToRegisterType(processor, instructions, type, receiveMethod);
+                        var versionMethod = new GenericInstanceMethod(m_MessagingSystem_CreateMessageAndGetVersion_MethodRef);
+                        versionMethod.GenericArguments.Add(type);
+                        CreateInstructionsToRegisterType(processor, instructions, type, receiveMethod, versionMethod);
                     }
 
                     instructions.ForEach(instruction => processor.Body.Instructions.Insert(processor.Body.Instructions.Count - 1, instruction));

Editor/CodeGen/INetworkSerializableILPP.cs

@@ -10,7 +10,6 @@ using ILPPInterface = Unity.CompilationPipeline.Common.ILPostProcessing.ILPostPr
 
 namespace Unity.Netcode.Editor.CodeGen
 {
-
     internal sealed class INetworkSerializableILPP : ILPPInterface
     {
         public override ILPPInterface GetInstance() => this;
@@ -92,7 +91,7 @@ namespace Unity.Netcode.Editor.CodeGen
                 }
                 catch (Exception e)
                 {
-                    m_Diagnostics.AddError((e.ToString() + e.StackTrace.ToString()).Replace("\n", "|").Replace("\r", "|"));
+                    m_Diagnostics.AddError((e.ToString() + e.StackTrace).Replace("\n", "|").Replace("\r", "|"));
                 }
             }
             else

Editor/CodeGen/NetworkBehaviourILPP.cs

@@ -2,7 +2,6 @@ using System;
 using System.IO;
 using System.Linq;
 using System.Collections.Generic;
-using System.Reflection;
 using System.Runtime.CompilerServices;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
@@ -23,8 +22,7 @@ namespace Unity.Netcode.Editor.CodeGen
 
         public override ILPPInterface GetInstance() => this;
 
-        public override bool WillProcess(ICompiledAssembly compiledAssembly) =>
+        public override bool WillProcess(ICompiledAssembly compiledAssembly) => compiledAssembly.References.Any(filePath => Path.GetFileNameWithoutExtension(filePath) == CodeGenHelpers.RuntimeAssemblyName);
-            compiledAssembly.References.Any(filePath => Path.GetFileNameWithoutExtension(filePath) == CodeGenHelpers.RuntimeAssemblyName);
 
         private readonly List<DiagnosticMessage> m_Diagnostics = new List<DiagnosticMessage>();
 
@@ -35,7 +33,6 @@ namespace Unity.Netcode.Editor.CodeGen
                 return null;
             }
 
-
             m_Diagnostics.Clear();
 
             // read
@@ -46,11 +43,27 @@ namespace Unity.Netcode.Editor.CodeGen
                 return null;
             }
 
+            // modules
+            (m_UnityModule, m_NetcodeModule) = CodeGenHelpers.FindBaseModules(assemblyDefinition, m_AssemblyResolver);
+
+            if (m_UnityModule == null)
+            {
+                m_Diagnostics.AddError($"Cannot find Unity module: {CodeGenHelpers.UnityModuleName}");
+                return null;
+            }
+
+            if (m_NetcodeModule == null)
+            {
+                m_Diagnostics.AddError($"Cannot find Netcode module: {CodeGenHelpers.NetcodeModuleName}");
+                return null;
+            }
+
             // process
             var mainModule = assemblyDefinition.MainModule;
             if (mainModule != null)
             {
                 m_MainModule = mainModule;
+
                 if (ImportReferences(mainModule))
                 {
                     // process `NetworkBehaviour` types
@@ -60,10 +73,12 @@ namespace Unity.Netcode.Editor.CodeGen
                             .Where(t => t.IsSubclassOf(CodeGenHelpers.NetworkBehaviour_FullName))
                             .ToList()
                             .ForEach(b => ProcessNetworkBehaviour(b, compiledAssembly.Defines));
+
+                        CreateNetworkVariableTypeInitializers(assemblyDefinition);
                     }
                     catch (Exception e)
                     {
-                        m_Diagnostics.AddError((e.ToString() + e.StackTrace.ToString()).Replace("\n", "|").Replace("\r", "|"));
+                        m_Diagnostics.AddError((e.ToString() + e.StackTrace).Replace("\n", "|").Replace("\r", "|"));
                     }
                 }
                 else
@@ -92,7 +107,135 @@ namespace Unity.Netcode.Editor.CodeGen
             return new ILPostProcessResult(new InMemoryAssembly(pe.ToArray(), pdb.ToArray()), m_Diagnostics);
         }
 
+        private MethodDefinition GetOrCreateStaticConstructor(TypeDefinition typeDefinition)
+        {
+            var staticCtorMethodDef = typeDefinition.GetStaticConstructor();
+            if (staticCtorMethodDef == null)
+            {
+                staticCtorMethodDef = new MethodDefinition(
+                    ".cctor", // Static Constructor (constant-constructor)
+                    MethodAttributes.HideBySig |
+                    MethodAttributes.SpecialName |
+                    MethodAttributes.RTSpecialName |
+                    MethodAttributes.Static,
+                    typeDefinition.Module.TypeSystem.Void);
+                staticCtorMethodDef.Body.Instructions.Add(Instruction.Create(OpCodes.Ret));
+                typeDefinition.Methods.Add(staticCtorMethodDef);
+            }
+
+            return staticCtorMethodDef;
+        }
+
+        private bool IsMemcpyableType(TypeReference type)
+        {
+            foreach (var supportedType in BaseSupportedTypes)
+            {
+                if (type.FullName == supportedType.FullName)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private bool IsSpecialCaseType(TypeReference type)
+        {
+            foreach (var supportedType in SpecialCaseTypes)
+            {
+                if (type.FullName == supportedType.FullName)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private void CreateNetworkVariableTypeInitializers(AssemblyDefinition assembly)
+        {
+            foreach (var typeDefinition in assembly.MainModule.Types)
+            {
+                if (typeDefinition.FullName == "<Module>")
+                {
+                    var staticCtorMethodDef = GetOrCreateStaticConstructor(typeDefinition);
+
+                    var processor = staticCtorMethodDef.Body.GetILProcessor();
+
+                    var instructions = new List<Instruction>();
+
+                    foreach (var type in m_WrappedNetworkVariableTypes)
+                    {
+                        if (IsSpecialCaseType(type))
+                        {
+                            continue;
+                        }
+
+                        // If a serializable type isn't found, FallbackSerializer will be used automatically, which will
+                        // call into UserNetworkVariableSerialization, giving the user a chance to define their own serializaiton
+                        // for types that aren't in our official supported types list.
+                        GenericInstanceMethod serializeMethod = null;
+                        GenericInstanceMethod equalityMethod;
+
+                        if (type.IsValueType)
+                        {
+                            if (type.HasInterface(typeof(INetworkSerializeByMemcpy).FullName) || type.Resolve().IsEnum || IsMemcpyableType(type))
+                            {
+                                serializeMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeSerializer_UnmanagedByMemcpy_MethodRef);
+                            }
+                            else if (type.HasInterface(typeof(INetworkSerializable).FullName))
+                            {
+                                serializeMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeSerializer_UnmanagedINetworkSerializable_MethodRef);
+                            }
+                            else if (type.HasInterface(CodeGenHelpers.IUTF8Bytes_FullName) && type.HasInterface(k_INativeListBool_FullName))
+                            {
+                                serializeMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeSerializer_FixedString_MethodRef);
+                            }
+
+                            if (type.HasInterface(typeof(IEquatable<>).FullName + "<" + type.FullName + ">"))
+                            {
+                                equalityMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeEqualityChecker_UnmanagedIEquatable_MethodRef);
+                            }
+                            else
+                            {
+                                equalityMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeEqualityChecker_UnmanagedValueEquals_MethodRef);
+                            }
+                        }
+                        else
+                        {
+                            if (type.HasInterface(typeof(INetworkSerializable).FullName))
+                            {
+                                serializeMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeSerializer_ManagedINetworkSerializable_MethodRef);
+                            }
+
+                            if (type.HasInterface(typeof(IEquatable<>).FullName + "<" + type.FullName + ">"))
+                            {
+                                equalityMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeEqualityChecker_ManagedIEquatable_MethodRef);
+                            }
+                            else
+                            {
+                                equalityMethod = new GenericInstanceMethod(m_NetworkVariableSerializationTypes_InitializeEqualityChecker_ManagedClassEquals_MethodRef);
+                            }
+                        }
+
+                        if (serializeMethod != null)
+                        {
+                            serializeMethod.GenericArguments.Add(type);
+                            instructions.Add(processor.Create(OpCodes.Call, m_MainModule.ImportReference(serializeMethod)));
+                        }
+                        equalityMethod.GenericArguments.Add(type);
+                        instructions.Add(processor.Create(OpCodes.Call, m_MainModule.ImportReference(equalityMethod)));
+                    }
+
+                    instructions.ForEach(instruction => processor.Body.Instructions.Insert(processor.Body.Instructions.Count - 1, instruction));
+                    break;
+                }
+            }
+        }
+
         private ModuleDefinition m_MainModule;
+        private ModuleDefinition m_UnityModule;
+        private ModuleDefinition m_NetcodeModule;
         private PostProcessorAssemblyResolver m_AssemblyResolver;
 
         private MethodReference m_Debug_LogError_MethodRef;
@@ -123,14 +266,76 @@ namespace Unity.Netcode.Editor.CodeGen
         private FieldReference m_ServerRpcParams_Receive_FieldRef;
         private FieldReference m_ServerRpcParams_Receive_SenderClientId_FieldRef;
         private TypeReference m_ClientRpcParams_TypeRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeSerializer_UnmanagedByMemcpy_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeSerializer_UnmanagedINetworkSerializable_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeSerializer_ManagedINetworkSerializable_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeSerializer_FixedString_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeEqualityChecker_ManagedIEquatable_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeEqualityChecker_UnmanagedIEquatable_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeEqualityChecker_UnmanagedValueEquals_MethodRef;
+        private MethodReference m_NetworkVariableSerializationTypes_InitializeEqualityChecker_ManagedClassEquals_MethodRef;
+
+        private MethodReference m_BytePacker_WriteValueBitPacked_Short_MethodRef;
+        private MethodReference m_BytePacker_WriteValueBitPacked_UShort_MethodRef;
+        private MethodReference m_BytePacker_WriteValueBitPacked_Int_MethodRef;
+        private MethodReference m_BytePacker_WriteValueBitPacked_UInt_MethodRef;
+        private MethodReference m_BytePacker_WriteValueBitPacked_Long_MethodRef;
+        private MethodReference m_BytePacker_WriteValueBitPacked_ULong_MethodRef;
+
+        private MethodReference m_ByteUnpacker_ReadValueBitPacked_Short_MethodRef;
+        private MethodReference m_ByteUnpacker_ReadValueBitPacked_UShort_MethodRef;
+        private MethodReference m_ByteUnpacker_ReadValueBitPacked_Int_MethodRef;
+        private MethodReference m_ByteUnpacker_ReadValueBitPacked_UInt_MethodRef;
+        private MethodReference m_ByteUnpacker_ReadValueBitPacked_Long_MethodRef;
+        private MethodReference m_ByteUnpacker_ReadValueBitPacked_ULong_MethodRef;
 
         private TypeReference m_FastBufferWriter_TypeRef;
-        private Dictionary<string, MethodReference> m_FastBufferWriter_WriteValue_MethodRefs = new Dictionary<string, MethodReference>();
+        private readonly Dictionary<string, MethodReference> m_FastBufferWriter_WriteValue_MethodRefs = new Dictionary<string, MethodReference>();
-        private List<MethodReference> m_FastBufferWriter_ExtensionMethodRefs = new List<MethodReference>();
+        private readonly List<MethodReference> m_FastBufferWriter_ExtensionMethodRefs = new List<MethodReference>();
 
         private TypeReference m_FastBufferReader_TypeRef;
-        private Dictionary<string, MethodReference> m_FastBufferReader_ReadValue_MethodRefs = new Dictionary<string, MethodReference>();
+        private readonly Dictionary<string, MethodReference> m_FastBufferReader_ReadValue_MethodRefs = new Dictionary<string, MethodReference>();
-        private List<MethodReference> m_FastBufferReader_ExtensionMethodRefs = new List<MethodReference>();
+        private readonly List<MethodReference> m_FastBufferReader_ExtensionMethodRefs = new List<MethodReference>();
+
+        private HashSet<TypeReference> m_WrappedNetworkVariableTypes = new HashSet<TypeReference>();
+
+        internal static readonly Type[] BaseSupportedTypes = new[]
+        {
+            typeof(bool),
+            typeof(byte),
+            typeof(sbyte),
+            typeof(char),
+            typeof(decimal),
+            typeof(double),
+            typeof(float),
+            // the following types have special handling
+            /*typeof(int),
+            typeof(uint),
+            typeof(long),
+            typeof(ulong),
+            typeof(short),
+            typeof(ushort),*/
+            typeof(Vector2),
+            typeof(Vector3),
+            typeof(Vector2Int),
+            typeof(Vector3Int),
+            typeof(Vector4),
+            typeof(Quaternion),
+            typeof(Color),
+            typeof(Color32),
+            typeof(Ray),
+            typeof(Ray2D)
+        };
+        internal static readonly Type[] SpecialCaseTypes = new[]
+        {
+            // the following types have special handling
+            typeof(int),
+            typeof(uint),
+            typeof(long),
+            typeof(ulong),
+            typeof(short),
+            typeof(ushort),
+        };
 
         private const string k_Debug_LogError = nameof(Debug.LogError);
         private const string k_NetworkManager_LocalClientId = nameof(NetworkManager.LocalClientId);
@@ -157,160 +362,257 @@ namespace Unity.Netcode.Editor.CodeGen
         private const string k_ServerRpcParams_Receive = nameof(ServerRpcParams.Receive);
         private const string k_ServerRpcReceiveParams_SenderClientId = nameof(ServerRpcReceiveParams.SenderClientId);
 
+        // CodeGen cannot reference the collections assembly to do a typeof() on it due to a bug that causes that to crash.
+        private const string k_INativeListBool_FullName = "Unity.Collections.INativeList`1<System.Byte>";
+
         private bool ImportReferences(ModuleDefinition moduleDefinition)
         {
-            var debugType = typeof(Debug);
+            TypeDefinition debugTypeDef = null;
-            foreach (var methodInfo in debugType.GetMethods())
+            foreach (var unityTypeDef in m_UnityModule.GetAllTypes())
             {
-                switch (methodInfo.Name)
+                if (debugTypeDef == null && unityTypeDef.FullName == typeof(Debug).FullName)
+                {
+                    debugTypeDef = unityTypeDef;
+                    continue;
+                }
+            }
+
+            TypeDefinition networkManagerTypeDef = null;
+            TypeDefinition networkBehaviourTypeDef = null;
+            TypeDefinition networkHandlerDelegateTypeDef = null;
+            TypeDefinition rpcParamsTypeDef = null;
+            TypeDefinition serverRpcParamsTypeDef = null;
+            TypeDefinition clientRpcParamsTypeDef = null;
+            TypeDefinition fastBufferWriterTypeDef = null;
+            TypeDefinition fastBufferReaderTypeDef = null;
+            TypeDefinition networkVariableSerializationTypesTypeDef = null;
+            TypeDefinition bytePackerTypeDef = null;
+            TypeDefinition byteUnpackerTypeDef = null;
+            foreach (var netcodeTypeDef in m_NetcodeModule.GetAllTypes())
+            {
+                if (networkManagerTypeDef == null && netcodeTypeDef.Name == nameof(NetworkManager))
+                {
+                    networkManagerTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (networkBehaviourTypeDef == null && netcodeTypeDef.Name == nameof(NetworkBehaviour))
+                {
+                    networkBehaviourTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (networkHandlerDelegateTypeDef == null && netcodeTypeDef.Name == nameof(NetworkManager.RpcReceiveHandler))
+                {
+                    networkHandlerDelegateTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (rpcParamsTypeDef == null && netcodeTypeDef.Name == nameof(__RpcParams))
+                {
+                    rpcParamsTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (serverRpcParamsTypeDef == null && netcodeTypeDef.Name == nameof(ServerRpcParams))
+                {
+                    serverRpcParamsTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (clientRpcParamsTypeDef == null && netcodeTypeDef.Name == nameof(ClientRpcParams))
+                {
+                    clientRpcParamsTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (fastBufferWriterTypeDef == null && netcodeTypeDef.Name == nameof(FastBufferWriter))
+                {
+                    fastBufferWriterTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (fastBufferReaderTypeDef == null && netcodeTypeDef.Name == nameof(FastBufferReader))
+                {
+                    fastBufferReaderTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (networkVariableSerializationTypesTypeDef == null && netcodeTypeDef.Name == nameof(NetworkVariableSerializationTypes))
+                {
+                    networkVariableSerializationTypesTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (bytePackerTypeDef == null && netcodeTypeDef.Name == nameof(BytePacker))
+                {
+                    bytePackerTypeDef = netcodeTypeDef;
+                    continue;
+                }
+
+                if (byteUnpackerTypeDef == null && netcodeTypeDef.Name == nameof(ByteUnpacker))
+                {
+                    byteUnpackerTypeDef = netcodeTypeDef;
+                    continue;
+                }
+            }
+
+            foreach (var methodDef in debugTypeDef.Methods)
+            {
+                switch (methodDef.Name)
                 {
                     case k_Debug_LogError:
-                        if (methodInfo.GetParameters().Length == 1)
+                        if (methodDef.Parameters.Count == 1)
                         {
-                            m_Debug_LogError_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                            m_Debug_LogError_MethodRef = moduleDefinition.ImportReference(methodDef);
                         }
 
                         break;
                 }
             }
 
-            var networkManagerType = typeof(NetworkManager);
+            m_NetworkManager_TypeRef = moduleDefinition.ImportReference(networkManagerTypeDef);
-            m_NetworkManager_TypeRef = moduleDefinition.ImportReference(networkManagerType);
+            foreach (var propertyDef in networkManagerTypeDef.Properties)
-            foreach (var propertyInfo in networkManagerType.GetProperties())
             {
-                switch (propertyInfo.Name)
+                switch (propertyDef.Name)
                 {
                     case k_NetworkManager_LocalClientId:
-                        m_NetworkManager_getLocalClientId_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkManager_getLocalClientId_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                     case k_NetworkManager_IsListening:
-                        m_NetworkManager_getIsListening_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkManager_getIsListening_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                     case k_NetworkManager_IsHost:
-                        m_NetworkManager_getIsHost_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkManager_getIsHost_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                     case k_NetworkManager_IsServer:
-                        m_NetworkManager_getIsServer_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkManager_getIsServer_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                     case k_NetworkManager_IsClient:
-                        m_NetworkManager_getIsClient_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkManager_getIsClient_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                 }
             }
 
-            foreach (var fieldInfo in networkManagerType.GetFields(BindingFlags.Static | BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public))
+            foreach (var fieldDef in networkManagerTypeDef.Fields)
             {
-                switch (fieldInfo.Name)
+                switch (fieldDef.Name)
                 {
                     case k_NetworkManager_LogLevel:
-                        m_NetworkManager_LogLevel_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_NetworkManager_LogLevel_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                     case k_NetworkManager_rpc_func_table:
-                        m_NetworkManager_rpc_func_table_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_NetworkManager_rpc_func_table_FieldRef = moduleDefinition.ImportReference(fieldDef);
-                        m_NetworkManager_rpc_func_table_Add_MethodRef = moduleDefinition.ImportReference(fieldInfo.FieldType.GetMethod("Add"));
+
+                        m_NetworkManager_rpc_func_table_Add_MethodRef = fieldDef.FieldType.Resolve().Methods.First(m => m.Name == "Add");
+                        m_NetworkManager_rpc_func_table_Add_MethodRef.DeclaringType = fieldDef.FieldType;
+                        m_NetworkManager_rpc_func_table_Add_MethodRef = moduleDefinition.ImportReference(m_NetworkManager_rpc_func_table_Add_MethodRef);
                         break;
                     case k_NetworkManager_rpc_name_table:
-                        m_NetworkManager_rpc_name_table_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_NetworkManager_rpc_name_table_FieldRef = moduleDefinition.ImportReference(fieldDef);
-                        m_NetworkManager_rpc_name_table_Add_MethodRef = moduleDefinition.ImportReference(fieldInfo.FieldType.GetMethod("Add"));
+
+                        m_NetworkManager_rpc_name_table_Add_MethodRef = fieldDef.FieldType.Resolve().Methods.First(m => m.Name == "Add");
+                        m_NetworkManager_rpc_name_table_Add_MethodRef.DeclaringType = fieldDef.FieldType;
+                        m_NetworkManager_rpc_name_table_Add_MethodRef = moduleDefinition.ImportReference(m_NetworkManager_rpc_name_table_Add_MethodRef);
                         break;
                 }
             }
 
-            var networkBehaviourType = typeof(NetworkBehaviour);
+            m_NetworkBehaviour_TypeRef = moduleDefinition.ImportReference(networkBehaviourTypeDef);
-            m_NetworkBehaviour_TypeRef = moduleDefinition.ImportReference(networkBehaviourType);
+            foreach (var propertyDef in networkBehaviourTypeDef.Properties)
-            foreach (var propertyInfo in networkBehaviourType.GetProperties())
             {
-                switch (propertyInfo.Name)
+                switch (propertyDef.Name)
                 {
                     case k_NetworkBehaviour_NetworkManager:
-                        m_NetworkBehaviour_getNetworkManager_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkBehaviour_getNetworkManager_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                     case k_NetworkBehaviour_OwnerClientId:
-                        m_NetworkBehaviour_getOwnerClientId_MethodRef = moduleDefinition.ImportReference(propertyInfo.GetMethod);
+                        m_NetworkBehaviour_getOwnerClientId_MethodRef = moduleDefinition.ImportReference(propertyDef.GetMethod);
                         break;
                 }
             }
 
-            foreach (var methodInfo in networkBehaviourType.GetMethods(BindingFlags.Static | BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public))
+            foreach (var methodDef in networkBehaviourTypeDef.Methods)
             {
-                switch (methodInfo.Name)
+                switch (methodDef.Name)
                 {
                     case k_NetworkBehaviour_beginSendServerRpc:
-                        m_NetworkBehaviour_beginSendServerRpc_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_NetworkBehaviour_beginSendServerRpc_MethodRef = moduleDefinition.ImportReference(methodDef);
                         break;
                     case k_NetworkBehaviour_endSendServerRpc:
-                        m_NetworkBehaviour_endSendServerRpc_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_NetworkBehaviour_endSendServerRpc_MethodRef = moduleDefinition.ImportReference(methodDef);
                         break;
                     case k_NetworkBehaviour_beginSendClientRpc:
-                        m_NetworkBehaviour_beginSendClientRpc_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_NetworkBehaviour_beginSendClientRpc_MethodRef = moduleDefinition.ImportReference(methodDef);
                         break;
                     case k_NetworkBehaviour_endSendClientRpc:
-                        m_NetworkBehaviour_endSendClientRpc_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                        m_NetworkBehaviour_endSendClientRpc_MethodRef = moduleDefinition.ImportReference(methodDef);
                         break;
                 }
             }
 
-            foreach (var fieldInfo in networkBehaviourType.GetFields(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public))
+            foreach (var fieldDef in networkBehaviourTypeDef.Fields)
             {
-                switch (fieldInfo.Name)
+                switch (fieldDef.Name)
                 {
                     case k_NetworkBehaviour_rpc_exec_stage:
-                        m_NetworkBehaviour_rpc_exec_stage_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_NetworkBehaviour_rpc_exec_stage_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                 }
             }
 
-            var networkHandlerDelegateType = typeof(NetworkManager.RpcReceiveHandler);
+            foreach (var ctor in networkHandlerDelegateTypeDef.Resolve().GetConstructors())
-            m_NetworkHandlerDelegateCtor_MethodRef = moduleDefinition.ImportReference(networkHandlerDelegateType.GetConstructor(new[] { typeof(object), typeof(IntPtr) }));
-
-            var rpcParamsType = typeof(__RpcParams);
-            m_RpcParams_TypeRef = moduleDefinition.ImportReference(rpcParamsType);
-            foreach (var fieldInfo in rpcParamsType.GetFields())
             {
-                switch (fieldInfo.Name)
+                if (ctor.HasParameters &&
+                    ctor.Parameters.Count == 2 &&
+                    ctor.Parameters[0].ParameterType.Name == nameof(System.Object) &&
+                    ctor.Parameters[1].ParameterType.Name == nameof(IntPtr))
+                {
+                    m_NetworkHandlerDelegateCtor_MethodRef = moduleDefinition.ImportReference(ctor);
+                    break;
+                }
+            }
+
+            m_RpcParams_TypeRef = moduleDefinition.ImportReference(rpcParamsTypeDef);
+            foreach (var fieldDef in rpcParamsTypeDef.Fields)
+            {
+                switch (fieldDef.Name)
                 {
                     case k_RpcParams_Server:
-                        m_RpcParams_Server_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_RpcParams_Server_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                     case k_RpcParams_Client:
-                        m_RpcParams_Client_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_RpcParams_Client_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                 }
             }
 
-            var serverRpcParamsType = typeof(ServerRpcParams);
+            m_ServerRpcParams_TypeRef = moduleDefinition.ImportReference(serverRpcParamsTypeDef);
-            m_ServerRpcParams_TypeRef = moduleDefinition.ImportReference(serverRpcParamsType);
+            foreach (var fieldDef in serverRpcParamsTypeDef.Fields)
-            foreach (var fieldInfo in serverRpcParamsType.GetFields())
             {
-                switch (fieldInfo.Name)
+                switch (fieldDef.Name)
                 {
                     case k_ServerRpcParams_Receive:
-                        foreach (var recvFieldInfo in fieldInfo.FieldType.GetFields())
+                        foreach (var recvFieldDef in fieldDef.FieldType.Resolve().Fields)
                         {
-                            switch (recvFieldInfo.Name)
+                            switch (recvFieldDef.Name)
                             {
                                 case k_ServerRpcReceiveParams_SenderClientId:
-                                    m_ServerRpcParams_Receive_SenderClientId_FieldRef = moduleDefinition.ImportReference(recvFieldInfo);
+                                    m_ServerRpcParams_Receive_SenderClientId_FieldRef = moduleDefinition.ImportReference(recvFieldDef);
                                     break;
                             }
                         }
 
-                        m_ServerRpcParams_Receive_FieldRef = moduleDefinition.ImportReference(fieldInfo);
+                        m_ServerRpcParams_Receive_FieldRef = moduleDefinition.ImportReference(fieldDef);
                         break;
                 }
             }
 
-            var clientRpcParamsType = typeof(ClientRpcParams);
+            m_ClientRpcParams_TypeRef = moduleDefinition.ImportReference(clientRpcParamsTypeDef);
-            m_ClientRpcParams_TypeRef = moduleDefinition.ImportReference(clientRpcParamsType);
+            m_FastBufferWriter_TypeRef = moduleDefinition.ImportReference(fastBufferWriterTypeDef);
+            m_FastBufferReader_TypeRef = moduleDefinition.ImportReference(fastBufferReaderTypeDef);
 
-            var fastBufferWriterType = typeof(FastBufferWriter);
+            // Find all extension methods for FastBufferReader and FastBufferWriter to enable user-implemented methods to be called
-            m_FastBufferWriter_TypeRef = moduleDefinition.ImportReference(fastBufferWriterType);
-
-            var fastBufferReaderType = typeof(FastBufferReader);
-            m_FastBufferReader_TypeRef = moduleDefinition.ImportReference(fastBufferReaderType);
-
-            // Find all extension methods for FastBufferReader and FastBufferWriter to enable user-implemented
-            // methods to be called.
             var assemblies = new List<AssemblyDefinition> { m_MainModule.Assembly };
             foreach (var reference in m_MainModule.AssemblyReferences)
             {
@@ -371,9 +673,170 @@ namespace Unity.Netcode.Editor.CodeGen
                 }
             }
 
+            foreach (var method in networkVariableSerializationTypesTypeDef.Methods)
+            {
+                if (!method.IsStatic)
+                {
+                    continue;
+                }
+
+                switch (method.Name)
+                {
+                    case nameof(NetworkVariableSerializationTypes.InitializeSerializer_UnmanagedByMemcpy):
+                        m_NetworkVariableSerializationTypes_InitializeSerializer_UnmanagedByMemcpy_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeSerializer_UnmanagedINetworkSerializable):
+                        m_NetworkVariableSerializationTypes_InitializeSerializer_UnmanagedINetworkSerializable_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeSerializer_ManagedINetworkSerializable):
+                        m_NetworkVariableSerializationTypes_InitializeSerializer_ManagedINetworkSerializable_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeSerializer_FixedString):
+                        m_NetworkVariableSerializationTypes_InitializeSerializer_FixedString_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeEqualityChecker_ManagedIEquatable):
+                        m_NetworkVariableSerializationTypes_InitializeEqualityChecker_ManagedIEquatable_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeEqualityChecker_UnmanagedIEquatable):
+                        m_NetworkVariableSerializationTypes_InitializeEqualityChecker_UnmanagedIEquatable_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeEqualityChecker_UnmanagedValueEquals):
+                        m_NetworkVariableSerializationTypes_InitializeEqualityChecker_UnmanagedValueEquals_MethodRef = method;
+                        break;
+                    case nameof(NetworkVariableSerializationTypes.InitializeEqualityChecker_ManagedClassEquals):
+                        m_NetworkVariableSerializationTypes_InitializeEqualityChecker_ManagedClassEquals_MethodRef = method;
+                        break;
+                }
+            }
+
+            foreach (var method in bytePackerTypeDef.Methods)
+            {
+                if (!method.IsStatic)
+                {
+                    continue;
+                }
+
+                switch (method.Name)
+                {
+                    case nameof(BytePacker.WriteValueBitPacked):
+                        if (method.Parameters[1].ParameterType.FullName == typeof(short).FullName)
+                        {
+                            m_BytePacker_WriteValueBitPacked_Short_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(ushort).FullName)
+                        {
+                            m_BytePacker_WriteValueBitPacked_UShort_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(int).FullName)
+                        {
+                            m_BytePacker_WriteValueBitPacked_Int_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(uint).FullName)
+                        {
+                            m_BytePacker_WriteValueBitPacked_UInt_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(long).FullName)
+                        {
+                            m_BytePacker_WriteValueBitPacked_Long_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(ulong).FullName)
+                        {
+                            m_BytePacker_WriteValueBitPacked_ULong_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        break;
+                }
+            }
+
+            foreach (var method in byteUnpackerTypeDef.Methods)
+            {
+                if (!method.IsStatic)
+                {
+                    continue;
+                }
+
+                switch (method.Name)
+                {
+                    case nameof(ByteUnpacker.ReadValueBitPacked):
+                        if (method.Parameters[1].ParameterType.FullName == typeof(short).MakeByRefType().FullName)
+                        {
+                            m_ByteUnpacker_ReadValueBitPacked_Short_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(ushort).MakeByRefType().FullName)
+                        {
+                            m_ByteUnpacker_ReadValueBitPacked_UShort_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(int).MakeByRefType().FullName)
+                        {
+                            m_ByteUnpacker_ReadValueBitPacked_Int_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(uint).MakeByRefType().FullName)
+                        {
+                            m_ByteUnpacker_ReadValueBitPacked_UInt_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(long).MakeByRefType().FullName)
+                        {
+                            m_ByteUnpacker_ReadValueBitPacked_Long_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        else if (method.Parameters[1].ParameterType.FullName == typeof(ulong).MakeByRefType().FullName)
+                        {
+                            m_ByteUnpacker_ReadValueBitPacked_ULong_MethodRef = m_MainModule.ImportReference(method);
+                        }
+                        break;
+                }
+            }
+
             return true;
         }
 
+        // This gets all fields from this type as well as any parent types, up to (but not including) the base NetworkBehaviour class
+        // Importantly... this also resolves any generics, so if the base class is Foo<T> and contains a field of NetworkVariable<T>,
+        // and this class is Bar : Foo<int>, it will properly resolve NetworkVariable<T> to NetworkVariable<int>.
+        private void GetAllFieldsAndResolveGenerics(TypeDefinition type, ref List<TypeReference> fieldTypes, Dictionary<string, TypeReference> genericParameters = null)
+        {
+            foreach (var field in type.Fields)
+            {
+                if (field.FieldType.IsGenericInstance)
+                {
+                    var genericType = (GenericInstanceType)field.FieldType;
+                    var newGenericType = new GenericInstanceType(field.FieldType.Resolve());
+                    for (var i = 0; i < genericType.GenericArguments.Count; ++i)
+                    {
+                        var argument = genericType.GenericArguments[i];
+
+                        if (genericParameters != null && genericParameters.ContainsKey(argument.Name))
+                        {
+                            newGenericType.GenericArguments.Add(genericParameters[argument.Name]);
+                        }
+                        else
+                        {
+                            newGenericType.GenericArguments.Add(argument);
+                        }
+                    }
+                    fieldTypes.Add(newGenericType);
+                }
+                else
+                {
+                    fieldTypes.Add(field.FieldType);
+                }
+            }
+
+            if (type.BaseType == null || type.BaseType.Name == nameof(NetworkBehaviour))
+            {
+                return;
+            }
+            var genericParams = new Dictionary<string, TypeReference>();
+            var resolved = type.BaseType.Resolve();
+            if (type.BaseType.IsGenericInstance)
+            {
+                var genericType = (GenericInstanceType)type.BaseType;
+                for (var i = 0; i < genericType.GenericArguments.Count; ++i)
+                {
+                    genericParams[resolved.GenericParameters[i].Name] = genericType.GenericArguments[i];
+                }
+            }
+            GetAllFieldsAndResolveGenerics(resolved, ref fieldTypes, genericParams);
+        }
+
         private void ProcessNetworkBehaviour(TypeDefinition typeDefinition, string[] assemblyDefines)
         {
             var rpcHandlers = new List<(uint RpcMethodId, MethodDefinition RpcHandler)>();
@@ -416,6 +879,28 @@ namespace Unity.Netcode.Editor.CodeGen
                 }
             }
 
+            if (!typeDefinition.HasGenericParameters && !typeDefinition.IsGenericInstance)
+            {
+                var fieldTypes = new List<TypeReference>();
+                GetAllFieldsAndResolveGenerics(typeDefinition, ref fieldTypes);
+                foreach (var type in fieldTypes)
+                {
+                    //var type = field.FieldType;
+                    if (type.IsGenericInstance)
+                    {
+                        if (type.Resolve().Name == typeof(NetworkVariable<>).Name || type.Resolve().Name == typeof(NetworkList<>).Name)
+                        {
+                            var genericInstanceType = (GenericInstanceType)type;
+                            var wrappedType = genericInstanceType.GenericArguments[0];
+                            if (!m_WrappedNetworkVariableTypes.Contains(wrappedType))
+                            {
+                                m_WrappedNetworkVariableTypes.Add(wrappedType);
+                            }
+                        }
+                    }
+                }
+            }
+
             if (rpcHandlers.Count > 0 || rpcNames.Count > 0)
             {
                 var staticCtorMethodDef = typeDefinition.GetStaticConstructor();
@@ -656,6 +1141,36 @@ namespace Unity.Netcode.Editor.CodeGen
 
         private bool GetWriteMethodForParameter(TypeReference paramType, out MethodReference methodRef)
         {
+            if (paramType.FullName == typeof(short).FullName)
+            {
+                methodRef = m_BytePacker_WriteValueBitPacked_Short_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(ushort).FullName)
+            {
+                methodRef = m_BytePacker_WriteValueBitPacked_UShort_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(int).FullName)
+            {
+                methodRef = m_BytePacker_WriteValueBitPacked_Int_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(uint).FullName)
+            {
+                methodRef = m_BytePacker_WriteValueBitPacked_UInt_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(long).FullName)
+            {
+                methodRef = m_BytePacker_WriteValueBitPacked_Long_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(ulong).FullName)
+            {
+                methodRef = m_BytePacker_WriteValueBitPacked_ULong_MethodRef;
+                return true;
+            }
             var assemblyQualifiedName = paramType.FullName + ", " + paramType.Resolve().Module.Assembly.FullName;
             var foundMethodRef = m_FastBufferWriter_WriteValue_MethodRefs.TryGetValue(assemblyQualifiedName, out methodRef);
 
@@ -669,7 +1184,7 @@ namespace Unity.Netcode.Editor.CodeGen
                     {
                         if (parameters[1].IsIn)
                         {
-                            if (parameters[1].ParameterType.Resolve() == paramType.MakeByReferenceType().Resolve() &&
+                            if (((ByReferenceType)parameters[1].ParameterType).ElementType.FullName == paramType.FullName &&
                                 ((ByReferenceType)parameters[1].ParameterType).ElementType.IsArray == paramType.IsArray)
                             {
                                 methodRef = method;
@@ -679,8 +1194,7 @@ namespace Unity.Netcode.Editor.CodeGen
                         }
                         else
                         {
-
+                            if (parameters[1].ParameterType.FullName == paramType.FullName &&
-                            if (parameters[1].ParameterType.Resolve() == paramType.Resolve() &&
                                 parameters[1].ParameterType.IsArray == paramType.IsArray)
                             {
                                 methodRef = method;
@@ -803,6 +1317,36 @@ namespace Unity.Netcode.Editor.CodeGen
 
         private bool GetReadMethodForParameter(TypeReference paramType, out MethodReference methodRef)
         {
+            if (paramType.FullName == typeof(short).FullName)
+            {
+                methodRef = m_ByteUnpacker_ReadValueBitPacked_Short_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(ushort).FullName)
+            {
+                methodRef = m_ByteUnpacker_ReadValueBitPacked_UShort_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(int).FullName)
+            {
+                methodRef = m_ByteUnpacker_ReadValueBitPacked_Int_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(uint).FullName)
+            {
+                methodRef = m_ByteUnpacker_ReadValueBitPacked_UInt_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(long).FullName)
+            {
+                methodRef = m_ByteUnpacker_ReadValueBitPacked_Long_MethodRef;
+                return true;
+            }
+            if (paramType.FullName == typeof(ulong).FullName)
+            {
+                methodRef = m_ByteUnpacker_ReadValueBitPacked_ULong_MethodRef;
+                return true;
+            }
             var assemblyQualifiedName = paramType.FullName + ", " + paramType.Resolve().Module.Assembly.FullName;
 
             var foundMethodRef = m_FastBufferReader_ReadValue_MethodRefs.TryGetValue(assemblyQualifiedName, out methodRef);
@@ -813,7 +1357,7 @@ namespace Unity.Netcode.Editor.CodeGen
                     var parameters = method.Resolve().Parameters;
                     if (method.Name == k_ReadValueMethodName &&
                         parameters[1].IsOut &&
-                        parameters[1].ParameterType.Resolve() == paramType.MakeByReferenceType().Resolve() &&
+                        ((ByReferenceType)parameters[1].ParameterType).ElementType.FullName == paramType.FullName &&
                         ((ByReferenceType)parameters[1].ParameterType).ElementType.IsArray == paramType.IsArray)
                     {
                         methodRef = method;

Editor/Configuration.meta

@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: 2c61e8fe9a68a486fbbc3128d233ded2
+guid: 52153943c346dd04e8712ab540ab9c22
 folderAsset: yes
 DefaultImporter:
   externalObjects: {}

Editor/Configuration/NetcodeForGameObjectsSettings.cs

@@ -0,0 +1,39 @@
+using UnityEditor;
+
+
+namespace Unity.Netcode.Editor.Configuration
+{
+    internal class NetcodeForGameObjectsSettings
+    {
+        internal const string AutoAddNetworkObjectIfNoneExists = "AutoAdd-NetworkObject-When-None-Exist";
+        internal const string InstallMultiplayerToolsTipDismissedPlayerPrefKey = "Netcode_Tip_InstallMPTools_Dismissed";
+
+        internal static int GetNetcodeInstallMultiplayerToolTips()
+        {
+            if (EditorPrefs.HasKey(InstallMultiplayerToolsTipDismissedPlayerPrefKey))
+            {
+                return EditorPrefs.GetInt(InstallMultiplayerToolsTipDismissedPlayerPrefKey);
+            }
+            return 0;
+        }
+
+        internal static void SetNetcodeInstallMultiplayerToolTips(int toolTipPrefSetting)
+        {
+            EditorPrefs.SetInt(InstallMultiplayerToolsTipDismissedPlayerPrefKey, toolTipPrefSetting);
+        }
+
+        internal static bool GetAutoAddNetworkObjectSetting()
+        {
+            if (EditorPrefs.HasKey(AutoAddNetworkObjectIfNoneExists))
+            {
+                return EditorPrefs.GetBool(AutoAddNetworkObjectIfNoneExists);
+            }
+            return false;
+        }
+
+        internal static void SetAutoAddNetworkObjectSetting(bool autoAddSetting)
+        {
+            EditorPrefs.SetBool(AutoAddNetworkObjectIfNoneExists, autoAddSetting);
+        }
+    }
+}

Editor/Configuration/NetcodeForGameObjectsSettings.cs.meta

@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: c2e5a740c1abd4315801e3f26ecf8adb
+guid: 2f9c9b10bc41a0e46ab71324dd0ac6e1
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2

Editor/Configuration/NetcodeSettingsProvider.cs

@@ -0,0 +1,94 @@
+using UnityEditor;
+using UnityEngine;
+
+namespace Unity.Netcode.Editor.Configuration
+{
+    internal static class NetcodeSettingsProvider
+    {
+        [SettingsProvider]
+        public static SettingsProvider CreateNetcodeSettingsProvider()
+        {
+            // First parameter is the path in the Settings window.
+            // Second parameter is the scope of this setting: it only appears in the Settings window for the Project scope.
+            var provider = new SettingsProvider("Project/NetcodeForGameObjects", SettingsScope.Project)
+            {
+                label = "Netcode for GameObjects",
+                keywords = new[] { "netcode", "editor" },
+                guiHandler = OnGuiHandler,
+            };
+
+            return provider;
+        }
+
+        internal static NetcodeSettingsLabel NetworkObjectsSectionLabel = new NetcodeSettingsLabel("NetworkObject Helper Settings", 20);
+        internal static NetcodeSettingsToggle AutoAddNetworkObjectToggle = new NetcodeSettingsToggle("Auto-Add NetworkObjects", "When enabled, NetworkObjects are automatically added to GameObjects when NetworkBehaviours are added first.", 20);
+        internal static NetcodeSettingsLabel MultiplayerToolsLabel = new NetcodeSettingsLabel("Multiplayer Tools", 20);
+        internal static NetcodeSettingsToggle MultiplayerToolTipStatusToggle = new NetcodeSettingsToggle("Multiplayer Tools Install Reminder", "When enabled, the NetworkManager will display " +
+            "the notification to install the multiplayer tools package.", 20);
+
+        private static void OnGuiHandler(string obj)
+        {
+            var autoAddNetworkObjectSetting = NetcodeForGameObjectsSettings.GetAutoAddNetworkObjectSetting();
+            var multiplayerToolsTipStatus = NetcodeForGameObjectsSettings.GetNetcodeInstallMultiplayerToolTips() == 0;
+            EditorGUI.BeginChangeCheck();
+            NetworkObjectsSectionLabel.DrawLabel();
+            autoAddNetworkObjectSetting = AutoAddNetworkObjectToggle.DrawToggle(autoAddNetworkObjectSetting);
+            MultiplayerToolsLabel.DrawLabel();
+            multiplayerToolsTipStatus = MultiplayerToolTipStatusToggle.DrawToggle(multiplayerToolsTipStatus);
+            if (EditorGUI.EndChangeCheck())
+            {
+                NetcodeForGameObjectsSettings.SetAutoAddNetworkObjectSetting(autoAddNetworkObjectSetting);
+                NetcodeForGameObjectsSettings.SetNetcodeInstallMultiplayerToolTips(multiplayerToolsTipStatus ? 0 : 1);
+            }
+        }
+    }
+
+    internal class NetcodeSettingsLabel : NetcodeGUISettings
+    {
+        private string m_LabelContent;
+
+        public void DrawLabel()
+        {
+            EditorGUIUtility.labelWidth = m_LabelSize;
+            GUILayout.Label(m_LabelContent, EditorStyles.boldLabel, m_LayoutWidth);
+        }
+
+        public NetcodeSettingsLabel(string labelText, float layoutOffset = 0.0f)
+        {
+            m_LabelContent = labelText;
+            AdjustLableSize(labelText, layoutOffset);
+        }
+    }
+
+    internal class NetcodeSettingsToggle : NetcodeGUISettings
+    {
+        private GUIContent m_ToggleContent;
+
+        public bool DrawToggle(bool currentSetting)
+        {
+            EditorGUIUtility.labelWidth = m_LabelSize;
+            return EditorGUILayout.Toggle(m_ToggleContent, currentSetting, m_LayoutWidth);
+        }
+
+        public NetcodeSettingsToggle(string labelText, string toolTip, float layoutOffset)
+        {
+            AdjustLableSize(labelText, layoutOffset);
+            m_ToggleContent = new GUIContent(labelText, toolTip);
+        }
+    }
+
+    internal class NetcodeGUISettings
+    {
+        private const float k_MaxLabelWidth = 450f;
+        protected float m_LabelSize { get; private set; }
+
+        protected GUILayoutOption m_LayoutWidth { get; private set; }
+
+        protected void AdjustLableSize(string labelText, float offset = 0.0f)
+        {
+            m_LabelSize = Mathf.Min(k_MaxLabelWidth, EditorStyles.label.CalcSize(new GUIContent(labelText)).x);
+            m_LayoutWidth = GUILayout.Width(m_LabelSize + offset);
+        }
+    }
+
+}

Editor/Configuration/NetcodeSettingsProvider.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 6b373a89fcbd41444a97ebd1798b326f
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Editor/HiddenScriptEditor.cs

@@ -0,0 +1,81 @@
+using Unity.Netcode.Components;
+#if UNITY_UNET_PRESENT
+using Unity.Netcode.Transports.UNET;
+#endif
+using Unity.Netcode.Transports.UTP;
+using UnityEditor;
+
+namespace Unity.Netcode.Editor
+{
+    /// <summary>
+    /// Internal use. Hides the script field for the given component.
+    /// </summary>
+    public class HiddenScriptEditor : UnityEditor.Editor
+    {
+        private static readonly string[] k_HiddenFields = { "m_Script" };
+
+        /// <summary>
+        /// Draws inspector properties without the script field.
+        /// </summary>
+        public override void OnInspectorGUI()
+        {
+            EditorGUI.BeginChangeCheck();
+            serializedObject.UpdateIfRequiredOrScript();
+            DrawPropertiesExcluding(serializedObject, k_HiddenFields);
+            serializedObject.ApplyModifiedProperties();
+            EditorGUI.EndChangeCheck();
+        }
+    }
+#if UNITY_UNET_PRESENT
+    /// <summary>
+    /// Internal use. Hides the script field for UNetTransport.
+    /// </summary>
+    [CustomEditor(typeof(UNetTransport), true)]
+    public class UNetTransportEditor : HiddenScriptEditor
+    {
+
+    }
+#endif
+
+    /// <summary>
+    /// Internal use. Hides the script field for UnityTransport.
+    /// </summary>
+    [CustomEditor(typeof(UnityTransport), true)]
+    public class UnityTransportEditor : HiddenScriptEditor
+    {
+
+    }
+
+#if COM_UNITY_MODULES_ANIMATION
+    /// <summary>
+    /// Internal use. Hides the script field for NetworkAnimator.
+    /// </summary>
+    [CustomEditor(typeof(NetworkAnimator), true)]
+    public class NetworkAnimatorEditor : HiddenScriptEditor
+    {
+
+    }
+#endif
+
+#if COM_UNITY_MODULES_PHYSICS
+    /// <summary>
+    /// Internal use. Hides the script field for NetworkRigidbody.
+    /// </summary>
+    [CustomEditor(typeof(NetworkRigidbody), true)]
+    public class NetworkRigidbodyEditor : HiddenScriptEditor
+    {
+
+    }
+#endif
+
+#if COM_UNITY_MODULES_PHYSICS2D
+    /// <summary>
+    /// Internal use. Hides the script field for NetworkRigidbody2D.
+    /// </summary>
+    [CustomEditor(typeof(NetworkRigidbody2D), true)]
+    public class NetworkRigidbody2DEditor : HiddenScriptEditor
+    {
+
+    }
+#endif
+}

Editor/HiddenScriptEditor.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: ebf622cc80e94f488e59caf8b7419f50
+timeCreated: 1661959406

Editor/NetworkBehaviourEditor.cs

@@ -3,9 +3,13 @@ using System.Collections.Generic;
 using System.Reflection;
 using UnityEngine;
 using UnityEditor;
+using Unity.Netcode.Editor.Configuration;
 
 namespace Unity.Netcode.Editor
 {
+    /// <summary>
+    /// The <see cref="CustomEditor"/> for <see cref="NetworkBehaviour"/>
+    /// </summary>
     [CustomEditor(typeof(NetworkBehaviour), true)]
     [CanEditMultipleObjects]
     public class NetworkBehaviourEditor : UnityEditor.Editor
@@ -33,8 +37,8 @@ namespace Unity.Netcode.Editor
                 var ft = fields[i].FieldType;
                 if (ft.IsGenericType && ft.GetGenericTypeDefinition() == typeof(NetworkVariable<>) && !fields[i].IsDefined(typeof(HideInInspector), true))
                 {
-                    m_NetworkVariableNames.Add(fields[i].Name);
+                    m_NetworkVariableNames.Add(ObjectNames.NicifyVariableName(fields[i].Name));
-                    m_NetworkVariableFields.Add(fields[i].Name, fields[i]);
+                    m_NetworkVariableFields.Add(ObjectNames.NicifyVariableName(fields[i].Name), fields[i]);
                 }
             }
         }
@@ -151,6 +155,8 @@ namespace Unity.Netcode.Editor
             }
         }
 
+
+        /// <inheritdoc/>
         public override void OnInspectorGUI()
         {
             if (!m_Initialized)
@@ -228,8 +234,11 @@ namespace Unity.Netcode.Editor
             CheckForNetworkObject((target as NetworkBehaviour).gameObject);
         }
 
-        internal const string AutoAddNetworkObjectIfNoneExists = "AutoAdd-NetworkObject-When-None-Exist";
+        /// <summary>
-
+        /// Recursively finds the root parent of a <see cref="Transform"/>
+        /// </summary>
+        /// <param name="transform">The current <see cref="Transform"/> we are inspecting for a parent</param>
+        /// <returns>the root parent for the first <see cref="Transform"/> passed into the method</returns>
         public static Transform GetRootParentTransform(Transform transform)
         {
             if (transform.parent == null || transform.parent == transform)
@@ -244,6 +253,8 @@ namespace Unity.Netcode.Editor
         /// does not already have a NetworkObject component.  If not it will notify
         /// the user that NetworkBehaviours require a NetworkObject.
         /// </summary>
+        /// <param name="gameObject"><see cref="GameObject"/> to start checking for a <see cref="NetworkObject"/></param>
+        /// <param name="networkObjectRemoved">used internally</param>
         public static void CheckForNetworkObject(GameObject gameObject, bool networkObjectRemoved = false)
         {
             // If there are no NetworkBehaviours or no gameObject, then exit early
@@ -254,8 +265,7 @@ namespace Unity.Netcode.Editor
 
             // Now get the root parent transform to the current GameObject (or itself)
             var rootTransform = GetRootParentTransform(gameObject.transform);
-            var networkManager = rootTransform.GetComponent<NetworkManager>();
+            if (!rootTransform.TryGetComponent<NetworkManager>(out var networkManager))
-            if (networkManager == null)
             {
                 networkManager = rootTransform.GetComponentInChildren<NetworkManager>();
             }
@@ -290,8 +300,7 @@ namespace Unity.Netcode.Editor
 
             // Otherwise, check to see if there is any NetworkObject from the root GameObject down to all children.
             // If not, notify the user that NetworkBehaviours require that the relative GameObject has a NetworkObject component.
-            var networkObject = rootTransform.GetComponent<NetworkObject>();
+            if (!rootTransform.TryGetComponent<NetworkObject>(out var networkObject))
-            if (networkObject == null)
             {
                 networkObject = rootTransform.GetComponentInChildren<NetworkObject>();
 
@@ -301,7 +310,7 @@ namespace Unity.Netcode.Editor
                     // and the user has already turned "Auto-Add NetworkObject" on when first notified about the requirement
                     // then just send a reminder to the user why the NetworkObject they just deleted seemingly "re-appeared"
                     // again.
-                    if (networkObjectRemoved && EditorPrefs.HasKey(AutoAddNetworkObjectIfNoneExists) && EditorPrefs.GetBool(AutoAddNetworkObjectIfNoneExists))
+                    if (networkObjectRemoved && NetcodeForGameObjectsSettings.GetAutoAddNetworkObjectSetting())
                     {
                         Debug.LogWarning($"{gameObject.name} still has {nameof(NetworkBehaviour)}s and Auto-Add NetworkObjects is enabled. A NetworkObject is being added back to {gameObject.name}.");
                         Debug.Log($"To reset Auto-Add NetworkObjects: Select the Netcode->General->Reset Auto-Add NetworkObject menu item.");
@@ -310,7 +319,7 @@ namespace Unity.Netcode.Editor
                     // Notify and provide the option to add it one time, always add a NetworkObject, or do nothing and let the user manually add it
                     if (EditorUtility.DisplayDialog($"{nameof(NetworkBehaviour)}s require a {nameof(NetworkObject)}",
                     $"{gameObject.name} does not have a {nameof(NetworkObject)} component.  Would you like to add one now?", "Yes", "No (manually add it)",
-                    DialogOptOutDecisionType.ForThisMachine, AutoAddNetworkObjectIfNoneExists))
+                    DialogOptOutDecisionType.ForThisMachine, NetcodeForGameObjectsSettings.AutoAddNetworkObjectIfNoneExists))
                     {
                         gameObject.AddComponent<NetworkObject>();
                         var activeScene = UnityEngine.SceneManagement.SceneManager.GetActiveScene();
@@ -320,20 +329,5 @@ namespace Unity.Netcode.Editor
                 }
             }
         }
-
-        /// <summary>
-        /// This allows users to reset the Auto-Add NetworkObject preference
-        /// so the next time they add a NetworkBehaviour to a GameObject without
-        /// a NetworkObject it will display the dialog box again and not
-        /// automatically add a NetworkObject.
-        /// </summary>
-        [MenuItem("Netcode/General/Reset Auto-Add NetworkObject", false, 1)]
-        private static void ResetMultiplayerToolsTipStatus()
-        {
-            if (EditorPrefs.HasKey(AutoAddNetworkObjectIfNoneExists))
-            {
-                EditorPrefs.SetBool(AutoAddNetworkObjectIfNoneExists, false);
-            }
-        }
     }
 }

Editor/NetworkManagerEditor.cs

@@ -3,14 +3,18 @@ using System.Collections.Generic;
 using UnityEditor;
 using UnityEngine;
 using UnityEditorInternal;
+using Unity.Netcode.Editor.Configuration;
 
 namespace Unity.Netcode.Editor
 {
+    /// <summary>
+    /// This <see cref="CustomEditor"/> handles the translation between the <see cref="NetworkConfig"/> and
+    /// the <see cref="NetworkManager"/> properties.
+    /// </summary>
     [CustomEditor(typeof(NetworkManager), true)]
     [CanEditMultipleObjects]
     public class NetworkManagerEditor : UnityEditor.Editor
     {
-        internal const string InstallMultiplayerToolsTipDismissedPlayerPrefKey = "Netcode_Tip_InstallMPTools_Dismissed";
         private static GUIStyle s_CenteredWordWrappedLabelStyle;
         private static GUIStyle s_HelpBoxStyle;
 
@@ -200,6 +204,7 @@ namespace Unity.Netcode.Editor
             m_NetworkPrefabsList.drawHeaderCallback = rect => EditorGUI.LabelField(rect, "NetworkPrefabs");
         }
 
+        /// <inheritdoc/>
         public override void OnInspectorGUI()
         {
             Initialize();
@@ -209,18 +214,6 @@ namespace Unity.Netcode.Editor
             DrawInstallMultiplayerToolsTip();
 #endif
 
-            {
-                var iterator = serializedObject.GetIterator();
-
-                for (bool enterChildren = true; iterator.NextVisible(enterChildren); enterChildren = false)
-                {
-                    using (new EditorGUI.DisabledScope("m_Script" == iterator.propertyPath))
-                    {
-                        EditorGUILayout.PropertyField(iterator, false);
-                    }
-                }
-            }
-
             if (!m_NetworkManager.IsServer && !m_NetworkManager.IsClient)
             {
                 serializedObject.Update();
@@ -366,7 +359,7 @@ namespace Unity.Netcode.Editor
             const string targetUrl = "https://docs-multiplayer.unity3d.com/netcode/current/tools/install-tools";
             const string infoIconName = "console.infoicon";
 
-            if (PlayerPrefs.GetInt(InstallMultiplayerToolsTipDismissedPlayerPrefKey, 0) != 0)
+            if (NetcodeForGameObjectsSettings.GetNetcodeInstallMultiplayerToolTips() != 0)
             {
                 return;
             }
@@ -412,7 +405,7 @@ namespace Unity.Netcode.Editor
                 GUILayout.FlexibleSpace();
                 if (GUILayout.Button(dismissButtonText, dismissButtonStyle, GUILayout.ExpandWidth(false)))
                 {
-                    PlayerPrefs.SetInt(InstallMultiplayerToolsTipDismissedPlayerPrefKey, 1);
+                    NetcodeForGameObjectsSettings.SetNetcodeInstallMultiplayerToolTips(1);
                 }
                 EditorGUIUtility.AddCursorRect(GUILayoutUtility.GetLastRect(), MouseCursor.Link);
                 GUILayout.FlexibleSpace();

Editor/NetworkManagerHelper.cs

@@ -64,8 +64,12 @@ namespace Unity.Netcode.Editor
         {
             var scenesList = EditorBuildSettings.scenes.ToList();
             var activeScene = SceneManager.GetActiveScene();
-            var isSceneInBuildSettings = scenesList.Where((c) => c.path == activeScene.path).Count() == 1;
+            var isSceneInBuildSettings = scenesList.Count((c) => c.path == activeScene.path) == 1;
+#if UNITY_2023_1_OR_NEWER
+            var networkManager = Object.FindFirstObjectByType<NetworkManager>();
+#else
             var networkManager = Object.FindObjectOfType<NetworkManager>();
+#endif
             if (!isSceneInBuildSettings && networkManager != null)
             {
                 if (networkManager.NetworkConfig != null && networkManager.NetworkConfig.EnableSceneManagement)
@@ -109,9 +113,8 @@ namespace Unity.Netcode.Editor
         public void CheckAndNotifyUserNetworkObjectRemoved(NetworkManager networkManager, bool editorTest = false)
         {
             // Check for any NetworkObject at the same gameObject relative layer
-            var networkObject = networkManager.gameObject.GetComponent<NetworkObject>();
 
-            if (networkObject == null)
+            if (!networkManager.gameObject.TryGetComponent<NetworkObject>(out var networkObject))
             {
                 // if none is found, check to see if any children have a NetworkObject
                 networkObject = networkManager.gameObject.GetComponentInChildren<NetworkObject>();

Editor/NetworkObjectEditor.cs

@@ -4,6 +4,9 @@ using UnityEditor;
 
 namespace Unity.Netcode.Editor
 {
+    /// <summary>
+    /// The <see cref="CustomEditor"/> for <see cref="NetworkObject"/>
+    /// </summary>
     [CustomEditor(typeof(NetworkObject), true)]
     [CanEditMultipleObjects]
     public class NetworkObjectEditor : UnityEditor.Editor
@@ -12,6 +15,8 @@ namespace Unity.Netcode.Editor
         private NetworkObject m_NetworkObject;
         private bool m_ShowObservers;
 
+        private static readonly string[] k_HiddenFields = { "m_Script" };
+
         private void Initialize()
         {
             if (m_Initialized)
@@ -23,6 +28,7 @@ namespace Unity.Netcode.Editor
             m_NetworkObject = (NetworkObject)target;
         }
 
+        /// <inheritdoc/>
         public override void OnInspectorGUI()
         {
             Initialize();
@@ -91,7 +97,11 @@ namespace Unity.Netcode.Editor
             }
             else
             {
-                base.OnInspectorGUI();
+                EditorGUI.BeginChangeCheck();
+                serializedObject.UpdateIfRequiredOrScript();
+                DrawPropertiesExcluding(serializedObject, k_HiddenFields);
+                serializedObject.ApplyModifiedProperties();
+                EditorGUI.EndChangeCheck();
 
                 var guiEnabled = GUI.enabled;
                 GUI.enabled = false;

Editor/NetworkTransformEditor.cs

@@ -4,6 +4,9 @@ using Unity.Netcode.Components;
 
 namespace Unity.Netcode.Editor
 {
+    /// <summary>
+    /// The <see cref="CustomEditor"/> for <see cref="NetworkTransform"/>
+    /// </summary>
     [CustomEditor(typeof(NetworkTransform), true)]
     public class NetworkTransformEditor : UnityEditor.Editor
     {
@@ -28,6 +31,7 @@ namespace Unity.Netcode.Editor
         private static GUIContent s_RotationLabel = EditorGUIUtility.TrTextContent("Rotation");
         private static GUIContent s_ScaleLabel = EditorGUIUtility.TrTextContent("Scale");
 
+        /// <inheritdoc/>
         public void OnEnable()
         {
             m_SyncPositionXProperty = serializedObject.FindProperty(nameof(NetworkTransform.SyncPositionX));
@@ -46,6 +50,7 @@ namespace Unity.Netcode.Editor
             m_InterpolateProperty = serializedObject.FindProperty(nameof(NetworkTransform.Interpolate));
         }
 
+        /// <inheritdoc/>
         public override void OnInspectorGUI()
         {
             EditorGUILayout.LabelField("Syncing", EditorStyles.boldLabel);

Editor/com.unity.netcode.editor.asmdef

@@ -13,6 +13,26 @@
             "name": "com.unity.multiplayer.tools",
             "expression": "",
             "define": "MULTIPLAYER_TOOLS"
+        },
+        {
+            "name": "Unity",
+            "expression": "(0,2022.2.0a5)",
+            "define": "UNITY_UNET_PRESENT"
+        },
+        {
+            "name": "com.unity.modules.animation",
+            "expression": "",
+            "define": "COM_UNITY_MODULES_ANIMATION"
+        },
+        {
+            "name": "com.unity.modules.physics",
+            "expression": "",
+            "define": "COM_UNITY_MODULES_PHYSICS"
+        },
+        {
+            "name": "com.unity.modules.physics2d",
+            "expression": "",
+            "define": "COM_UNITY_MODULES_PHYSICS2D"
         }
     ]
 }

README.md

@@ -9,7 +9,7 @@ Netcode for GameObjects is a Unity package that provides networking capabilities
 
 Visit the [Multiplayer Docs Site](https://docs-multiplayer.unity3d.com/) for package & API documentation, as well as information about several samples which leverage the Netcode for GameObjects package.
 
-You can also jump right into our [Hello World](https://docs-multiplayer.unity3d.com/netcode/current/tutorials/helloworld/helloworldintro) guide for a taste of how to use the framework for basic networked tasks.
+You can also jump right into our [Hello World](https://docs-multiplayer.unity3d.com/netcode/current/tutorials/helloworld) guide for a taste of how to use the framework for basic networked tasks.
 
 ### Community and Feedback
 

Runtime/AssemblyInfo.cs

@@ -12,3 +12,4 @@ using System.Runtime.CompilerServices;
 [assembly: InternalsVisibleTo("Unity.Netcode.RuntimeTests")]
 [assembly: InternalsVisibleTo("Unity.Netcode.TestHelpers.Runtime")]
 [assembly: InternalsVisibleTo("Unity.Netcode.Adapter.UTP")]
+[assembly: InternalsVisibleTo("Unity.Multiplayer.Tools.Adapters.Ngo1WithUtp2")]

Runtime/Configuration/NetworkConfig.cs

@@ -150,8 +150,16 @@ namespace Unity.Netcode
         /// </summary>
         public bool EnableNetworkLogs = true;
 
+        /// <summary>
+        /// The number of RTT samples that is kept as an average for calculations
+        /// </summary>
         public const int RttAverageSamples = 5; // number of RTT to keep an average of (plus one)
+
+        /// <summary>
+        /// The number of slots used for RTT calculations. This is the maximum amount of in-flight messages
+        /// </summary>
         public const int RttWindowSize = 64; // number of slots to use for RTT computations (max number of in-flight packets)
+
         /// <summary>
         /// Returns a base64 encoded version of the configuration
         /// </summary>

Runtime/Core/NetworkBehaviour.cs

@@ -21,6 +21,7 @@ namespace Unity.Netcode
             Client = 2
         }
 
+
         // NetworkBehaviourILPP will override this in derived classes to return the name of the concrete type
         internal virtual string __getTypeName() => nameof(NetworkBehaviour);
 
@@ -235,16 +236,44 @@ namespace Unity.Netcode
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
             if (NetworkManager.__rpc_name_table.TryGetValue(rpcMethodId, out var rpcMethodName))
             {
-                foreach (var client in NetworkManager.ConnectedClients)
+                if (clientRpcParams.Send.TargetClientIds != null)
+                {
+                    foreach (var targetClientId in clientRpcParams.Send.TargetClientIds)
                     {
                         NetworkManager.NetworkMetrics.TrackRpcSent(
-                        client.Key,
+                            targetClientId,
                             NetworkObject,
                             rpcMethodName,
                             __getTypeName(),
                             rpcWriteSize);
                     }
                 }
+                else if (clientRpcParams.Send.TargetClientIdsNativeArray != null)
+                {
+                    foreach (var targetClientId in clientRpcParams.Send.TargetClientIdsNativeArray)
+                    {
+                        NetworkManager.NetworkMetrics.TrackRpcSent(
+                            targetClientId,
+                            NetworkObject,
+                            rpcMethodName,
+                            __getTypeName(),
+                            rpcWriteSize);
+                    }
+                }
+                else
+                {
+                    var observerEnumerator = NetworkObject.Observers.GetEnumerator();
+                    while (observerEnumerator.MoveNext())
+                    {
+                        NetworkManager.NetworkMetrics.TrackRpcSent(
+                            observerEnumerator.Current,
+                            NetworkObject,
+                            rpcMethodName,
+                            __getTypeName(),
+                            rpcWriteSize);
+                    }
+                }
+            }
 #endif
         }
 
@@ -258,7 +287,18 @@ namespace Unity.Netcode
         /// Gets the NetworkManager that owns this NetworkBehaviour instance
         ///   See note around `NetworkObject` for how there is a chicken / egg problem when we are not initialized
         /// </summary>
-        public NetworkManager NetworkManager => NetworkObject.NetworkManager;
+        public NetworkManager NetworkManager
+        {
+            get
+            {
+                if (NetworkObject?.NetworkManager != null)
+                {
+                    return NetworkObject?.NetworkManager;
+                }
+
+                return NetworkManager.Singleton;
+            }
+        }
 
         /// <summary>
         /// If a NetworkObject is assigned, it will return whether or not this NetworkObject
@@ -307,31 +347,38 @@ namespace Unity.Netcode
                 m_NetworkObject.NetworkManager.IsServer;
         }
 
-        /// <summary>
-        /// Gets the NetworkObject that owns this NetworkBehaviour instance
         ///  TODO: this needs an overhaul.  It's expensive, it's ja little naive in how it looks for networkObject in
         ///   its parent and worst, it creates a puzzle if you are a NetworkBehaviour wanting to see if you're live or not
         ///   (e.g. editor code).  All you want to do is find out if NetworkManager is null, but to do that you
         ///   need NetworkObject, but if you try and grab NetworkObject and NetworkManager isn't up you'll get
         ///   the warning below.  This is why IsBehaviourEditable had to be created.  Matt was going to re-do
         ///   how NetworkObject works but it was close to the release and too risky to change
-        ///
+        /// <summary>
+        /// Gets the NetworkObject that owns this NetworkBehaviour instance
         /// </summary>
         public NetworkObject NetworkObject
         {
             get
+            {
+                try
                 {
                     if (m_NetworkObject == null)
                     {
                         m_NetworkObject = GetComponentInParent<NetworkObject>();
                     }
+                }
+                catch (Exception)
+                {
+                    return null;
+                }
 
                 // ShutdownInProgress check:
                 // This prevents an edge case scenario where the NetworkManager is shutting down but user code
                 // in Update and/or in FixedUpdate could still be checking NetworkBehaviour.NetworkObject directly (i.e. does it exist?)
                 // or NetworkBehaviour.IsSpawned (i.e. to early exit if not spawned) which, in turn, could generate several Warning messages
                 // per spawned NetworkObject.  Checking for ShutdownInProgress prevents these unnecessary LogWarning messages.
-                if (m_NetworkObject == null && (NetworkManager.Singleton == null || !NetworkManager.Singleton.ShutdownInProgress))
+                // We must check IsSpawned, otherwise a warning will be logged under certain valid conditions (see OnDestroy)
+                if (IsSpawned && m_NetworkObject == null && (NetworkManager.Singleton == null || !NetworkManager.Singleton.ShutdownInProgress))
                 {
                     if (NetworkLog.CurrentLogLevel <= LogLevel.Normal)
                     {
@@ -435,15 +482,42 @@ namespace Unity.Netcode
             IsSpawned = true;
             InitializeVariables();
             UpdateNetworkProperties();
+        }
+
+        internal void VisibleOnNetworkSpawn()
+        {
+            try
+            {
                 OnNetworkSpawn();
             }
+            catch (Exception e)
+            {
+                Debug.LogException(e);
+            }
+
+            InitializeVariables();
+            if (IsServer)
+            {
+                // Since we just spawned the object and since user code might have modified their NetworkVariable, esp.
+                // NetworkList, we need to mark the object as free of updates.
+                // This should happen for all objects on the machine triggering the spawn.
+                PostNetworkVariableWrite(true);
+            }
+        }
 
         internal void InternalOnNetworkDespawn()
         {
             IsSpawned = false;
             UpdateNetworkProperties();
+            try
+            {
                 OnNetworkDespawn();
             }
+            catch (Exception e)
+            {
+                Debug.LogException(e);
+            }
+        }
 
         /// <summary>
         /// Gets called when the local client gains ownership of this object
@@ -470,6 +544,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Gets called when the parent NetworkObject of this NetworkBehaviour's NetworkObject has changed
         /// </summary>
+        /// <param name="parentNetworkObject">the new <see cref="NetworkObject"/> parent</param>
         public virtual void OnNetworkObjectParentChanged(NetworkObject parentNetworkObject) { }
 
         private bool m_VarInit = false;
@@ -574,7 +649,18 @@ namespace Unity.Netcode
             NetworkVariableIndexesToResetSet.Clear();
         }
 
-        internal void PostNetworkVariableWrite()
+        internal void PostNetworkVariableWrite(bool forced = false)
+        {
+            if (forced)
+            {
+                // Mark every variable as no longer dirty. We just spawned the object and whatever the game code did
+                // during OnNetworkSpawn has been sent and needs to be cleared
+                for (int i = 0; i < NetworkVariableFields.Count; i++)
+                {
+                    NetworkVariableFields[i].ResetDirty();
+                }
+            }
+            else
             {
                 // mark any variables we wrote as no longer dirty
                 for (int i = 0; i < NetworkVariableIndexesToReset.Count; i++)
@@ -583,7 +669,10 @@ namespace Unity.Netcode
                 }
             }
 
-        internal void VariableUpdate(ulong targetClientId)
+            MarkVariablesDirty(false);
+        }
+
+        internal void PreVariableUpdate()
         {
             if (!m_VarInit)
             {
@@ -591,6 +680,10 @@ namespace Unity.Netcode
             }
 
             PreNetworkVariableWrite();
+        }
+
+        internal void VariableUpdate(ulong targetClientId)
+        {
             NetworkVariableUpdate(targetClientId, NetworkBehaviourId);
         }
 
@@ -637,7 +730,7 @@ namespace Unity.Netcode
                         var tmpWriter = new FastBufferWriter(MessagingSystem.NON_FRAGMENTED_MESSAGE_MAX_SIZE, Allocator.Temp, MessagingSystem.FRAGMENTED_MESSAGE_MAX_SIZE);
                         using (tmpWriter)
                         {
-                            message.Serialize(tmpWriter);
+                            message.Serialize(tmpWriter, message.Version);
                         }
                     }
                     else
@@ -662,14 +755,22 @@ namespace Unity.Netcode
             return false;
         }
 
-        internal void MarkVariablesDirty()
+        internal void MarkVariablesDirty(bool dirty)
         {
             for (int j = 0; j < NetworkVariableFields.Count; j++)
             {
-                NetworkVariableFields[j].SetDirty(true);
+                NetworkVariableFields[j].SetDirty(dirty);
             }
         }
 
+        /// <summary>
+        /// Synchronizes by setting only the NetworkVariable field values that the client has permission to read.
+        /// Note: This is only invoked when first synchronizing a NetworkBehaviour (i.e. late join or spawned NetworkObject)
+        /// </summary>
+        /// <remarks>
+        /// When NetworkConfig.EnsureNetworkVariableLengthSafety is enabled each NetworkVariable field will be preceded
+        /// by the number of bytes written for that specific field.
+        /// </remarks>
         internal void WriteNetworkVariableData(FastBufferWriter writer, ulong targetClientId)
         {
             if (NetworkVariableFields.Count == 0)
@@ -679,11 +780,17 @@ namespace Unity.Netcode
 
             for (int j = 0; j < NetworkVariableFields.Count; j++)
             {
-                bool canClientRead = NetworkVariableFields[j].CanClientRead(targetClientId);
 
-                if (canClientRead)
+                if (NetworkVariableFields[j].CanClientRead(targetClientId))
+                {
+                    if (NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
                     {
                         var writePos = writer.Position;
+                        // Note: This value can't be packed because we don't know how large it will be in advance
+                        // we reserve space for it, then write the data, then come back and fill in the space
+                        // to pack here, we'd have to write data to a temporary buffer and copy it in - which
+                        // isn't worth possibly saving one byte if and only if the data is less than 63 bytes long...
+                        // The way we do packing, any value > 63 in a ushort will use the full 2 bytes to represent.
                         writer.WriteValueSafe((ushort)0);
                         var startPos = writer.Position;
                         NetworkVariableFields[j].WriteField(writer);
@@ -693,13 +800,27 @@ namespace Unity.Netcode
                         writer.Seek(startPos + size);
                     }
                     else
+                    {
+                        NetworkVariableFields[j].WriteField(writer);
+                    }
+                }
+                else // Only if EnsureNetworkVariableLengthSafety, otherwise just skip
+                if (NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
                 {
                     writer.WriteValueSafe((ushort)0);
                 }
             }
         }
 
-        internal void SetNetworkVariableData(FastBufferReader reader)
+        /// <summary>
+        /// Synchronizes by setting only the NetworkVariable field values that the client has permission to read.
+        /// Note: This is only invoked when first synchronizing a NetworkBehaviour (i.e. late join or spawned NetworkObject)
+        /// </summary>
+        /// <remarks>
+        /// When NetworkConfig.EnsureNetworkVariableLengthSafety is enabled each NetworkVariable field will be preceded
+        /// by the number of bytes written for that specific field.
+        /// </remarks>
+        internal void SetNetworkVariableData(FastBufferReader reader, ulong clientId)
         {
             if (NetworkVariableFields.Count == 0)
             {
@@ -708,13 +829,23 @@ namespace Unity.Netcode
 
             for (int j = 0; j < NetworkVariableFields.Count; j++)
             {
-                reader.ReadValueSafe(out ushort varSize);
+                var varSize = (ushort)0;
+                var readStartPos = 0;
+                if (NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
+                {
+                    reader.ReadValueSafe(out varSize);
                     if (varSize == 0)
                     {
                         continue;
                     }
+                    readStartPos = reader.Position;
+                }
+                else // If the client cannot read this field, then skip it
+                if (!NetworkVariableFields[j].CanClientRead(clientId))
+                {
+                    continue;
+                }
 
-                var readStartPos = reader.Position;
                 NetworkVariableFields[j].ReadField(reader);
 
                 if (NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
@@ -751,8 +882,153 @@ namespace Unity.Netcode
             return NetworkManager.SpawnManager.SpawnedObjects.TryGetValue(networkId, out NetworkObject networkObject) ? networkObject : null;
         }
 
+        /// <summary>
+        /// Override this method if your derived NetworkBehaviour requires custom synchronization data.
+        /// Note: Use of this method is only for the initial client synchronization of NetworkBehaviours
+        /// and will increase the payload size for client synchronization and dynamically spawned
+        /// <see cref="NetworkObject"/>s.
+        /// </summary>
+        /// <remarks>
+        /// When serializing (writing) this will be invoked during the client synchronization period and
+        /// when spawning new NetworkObjects.
+        /// When deserializing (reading), this will be invoked prior to the NetworkBehaviour's associated
+        /// NetworkObject being spawned.
+        /// </remarks>
+        /// <param name="serializer">The serializer to use to read and write the data.</param>
+        /// <typeparam name="T">
+        /// Either BufferSerializerReader or BufferSerializerWriter, depending whether the serializer
+        /// is in read mode or write mode.
+        /// </typeparam>
+        protected virtual void OnSynchronize<T>(ref BufferSerializer<T> serializer) where T : IReaderWriter
+        {
+
+        }
+
+        /// <summary>
+        /// Internal method that determines if a NetworkBehaviour has additional synchronization data to
+        /// be synchronized when first instantiated prior to its associated NetworkObject being spawned.
+        /// </summary>
+        /// <remarks>
+        /// This includes try-catch blocks to recover from exceptions that might occur and continue to
+        /// synchronize any remaining NetworkBehaviours.
+        /// </remarks>
+        /// <returns>true if it wrote synchronization data and false if it did not</returns>
+        internal bool Synchronize<T>(ref BufferSerializer<T> serializer) where T : IReaderWriter
+        {
+            if (serializer.IsWriter)
+            {
+                // Get the writer to handle seeking and determining how many bytes were written
+                var writer = serializer.GetFastBufferWriter();
+                // Save our position before we attempt to write anything so we can seek back to it (i.e. error occurs)
+                var positionBeforeWrite = writer.Position;
+                writer.WriteValueSafe(NetworkBehaviourId);
+
+                // Save our position where we will write the final size being written so we can skip over it in the
+                // event an exception occurs when deserializing.
+                var sizePosition = writer.Position;
+                writer.WriteValueSafe((ushort)0);
+
+                // Save our position before synchronizing to determine how much was written
+                var positionBeforeSynchronize = writer.Position;
+                var threwException = false;
+                try
+                {
+                    OnSynchronize(ref serializer);
+                }
+                catch (Exception ex)
+                {
+                    threwException = true;
+                    if (NetworkManager.LogLevel <= LogLevel.Normal)
+                    {
+                        NetworkLog.LogWarning($"{name} threw an exception during synchronization serialization, this {nameof(NetworkBehaviour)} is being skipped and will not be synchronized!");
+                        if (NetworkManager.LogLevel == LogLevel.Developer)
+                        {
+                            NetworkLog.LogError($"{ex.Message}\n {ex.StackTrace}");
+                        }
+                    }
+                }
+                var finalPosition = writer.Position;
+
+                // If we wrote nothing then skip writing anything for this NetworkBehaviour
+                if (finalPosition == positionBeforeSynchronize || threwException)
+                {
+                    writer.Seek(positionBeforeWrite);
+                    return false;
+                }
+                else
+                {
+                    // Write the number of bytes serialized to handle exceptions on the deserialization side
+                    var bytesWritten = finalPosition - positionBeforeSynchronize;
+                    writer.Seek(sizePosition);
+                    writer.WriteValueSafe((ushort)bytesWritten);
+                    writer.Seek(finalPosition);
+                }
+                return true;
+            }
+            else
+            {
+                var reader = serializer.GetFastBufferReader();
+                // We will always read the expected byte count
+                reader.ReadValueSafe(out ushort expectedBytesToRead);
+
+                // Save our position before we begin synchronization deserialization
+                var positionBeforeSynchronize = reader.Position;
+                var synchronizationError = false;
+                try
+                {
+                    // Invoke synchronization
+                    OnSynchronize(ref serializer);
+                }
+                catch (Exception ex)
+                {
+                    if (NetworkManager.LogLevel <= LogLevel.Normal)
+                    {
+                        NetworkLog.LogWarning($"{name} threw an exception during synchronization deserialization, this {nameof(NetworkBehaviour)} is being skipped and will not be synchronized!");
+                        if (NetworkManager.LogLevel == LogLevel.Developer)
+                        {
+                            NetworkLog.LogError($"{ex.Message}\n {ex.StackTrace}");
+                        }
+                    }
+                    synchronizationError = true;
+                }
+
+                var totalBytesRead = reader.Position - positionBeforeSynchronize;
+                if (totalBytesRead != expectedBytesToRead)
+                {
+                    if (NetworkManager.LogLevel <= LogLevel.Normal)
+                    {
+                        NetworkLog.LogWarning($"{name} read {totalBytesRead} bytes but was expected to read {expectedBytesToRead} bytes during synchronization deserialization! This {nameof(NetworkBehaviour)} is being skipped and will not be synchronized!");
+                    }
+                    synchronizationError = true;
+                }
+
+                // Skip over the entry if deserialization fails
+                if (synchronizationError)
+                {
+                    var skipToPosition = positionBeforeSynchronize + expectedBytesToRead;
+                    reader.Seek(skipToPosition);
+                    return false;
+                }
+                return true;
+            }
+        }
+
+
+        /// <summary>
+        /// Invoked when the <see cref="GameObject"/> the <see cref="NetworkBehaviour"/> is attached to.
+        /// NOTE:  If you override this, you will want to always invoke this base class version of this
+        /// <see cref="OnDestroy"/> method!!
+        /// </summary>
         public virtual void OnDestroy()
         {
+            if (NetworkObject != null && NetworkObject.IsSpawned && IsSpawned)
+            {
+                // If the associated NetworkObject is still spawned then this
+                // NetworkBehaviour will be removed from the NetworkObject's
+                // ChildNetworkBehaviours list.
+                NetworkObject.OnNetworkBehaviourDestroyed(this);
+            }
+
             // this seems odd to do here, but in fact especially in tests we can find ourselves
             //  here without having called InitializedVariables, which causes problems if any
             //  of those variables use native containers (e.g. NetworkList) as they won't be
@@ -764,6 +1040,7 @@ namespace Unity.Netcode
                 InitializeVariables();
             }
 
+
             for (int i = 0; i < NetworkVariableFields.Count; i++)
             {
                 NetworkVariableFields[i].Dispose();

Runtime/Core/NetworkBehaviourUpdater.cs

@@ -3,14 +3,22 @@ using Unity.Profiling;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// An helper class that helps NetworkManager update NetworkBehaviours and replicate them down to connected clients.
+    /// </summary>
     public class NetworkBehaviourUpdater
     {
-        private HashSet<NetworkObject> m_Touched = new HashSet<NetworkObject>();
+        private HashSet<NetworkObject> m_DirtyNetworkObjects = new HashSet<NetworkObject>();
 
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
         private ProfilerMarker m_NetworkBehaviourUpdate = new ProfilerMarker($"{nameof(NetworkBehaviour)}.{nameof(NetworkBehaviourUpdate)}");
 #endif
 
+        internal void AddForUpdate(NetworkObject networkObject)
+        {
+            m_DirtyNetworkObjects.Add(networkObject);
+        }
+
         internal void NetworkBehaviourUpdate(NetworkManager networkManager)
         {
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
@@ -18,59 +26,58 @@ namespace Unity.Netcode
 #endif
             try
             {
+                // NetworkObject references can become null, when hidden or despawned. Once NUll, there is no point
+                // trying to process them, even if they were previously marked as dirty.
+                m_DirtyNetworkObjects.RemoveWhere((sobj) => sobj == null);
+
                 if (networkManager.IsServer)
                 {
-                    m_Touched.Clear();
+                    foreach (var dirtyObj in m_DirtyNetworkObjects)
+                    {
+                        for (int k = 0; k < dirtyObj.ChildNetworkBehaviours.Count; k++)
+                        {
+                            dirtyObj.ChildNetworkBehaviours[k].PreVariableUpdate();
+                        }
+
                         for (int i = 0; i < networkManager.ConnectedClientsList.Count; i++)
                         {
                             var client = networkManager.ConnectedClientsList[i];
-                        var spawnedObjs = networkManager.SpawnManager.SpawnedObjectsList;
+
-                        m_Touched.UnionWith(spawnedObjs);
+                            if (dirtyObj.IsNetworkVisibleTo(client.ClientId))
-                        foreach (var sobj in spawnedObjs)
-                        {
-                            if (sobj.IsNetworkVisibleTo(client.ClientId))
                             {
                                 // Sync just the variables for just the objects this client sees
-                                for (int k = 0; k < sobj.ChildNetworkBehaviours.Count; k++)
+                                for (int k = 0; k < dirtyObj.ChildNetworkBehaviours.Count; k++)
                                 {
-                                    sobj.ChildNetworkBehaviours[k].VariableUpdate(client.ClientId);
+                                    dirtyObj.ChildNetworkBehaviours[k].VariableUpdate(client.ClientId);
                                 }
                             }
                         }
                     }
-
-                    // Now, reset all the no-longer-dirty variables
-                    foreach (var sobj in m_Touched)
-                    {
-                        for (int k = 0; k < sobj.ChildNetworkBehaviours.Count; k++)
-                        {
-                            sobj.ChildNetworkBehaviours[k].PostNetworkVariableWrite();
-                        }
-                    }
                 }
                 else
                 {
                     // when client updates the server, it tells it about all its objects
-                    foreach (var sobj in networkManager.SpawnManager.SpawnedObjectsList)
+                    foreach (var sobj in m_DirtyNetworkObjects)
                     {
                         if (sobj.IsOwner)
                         {
+                            for (int k = 0; k < sobj.ChildNetworkBehaviours.Count; k++)
+                            {
+                                sobj.ChildNetworkBehaviours[k].PreVariableUpdate();
+                            }
                             for (int k = 0; k < sobj.ChildNetworkBehaviours.Count; k++)
                             {
                                 sobj.ChildNetworkBehaviours[k].VariableUpdate(NetworkManager.ServerClientId);
                             }
                         }
                     }
-
+                }
                 // Now, reset all the no-longer-dirty variables
-                    foreach (var sobj in networkManager.SpawnManager.SpawnedObjectsList)
+                foreach (var dirtyobj in m_DirtyNetworkObjects)
                 {
-                        for (int k = 0; k < sobj.ChildNetworkBehaviours.Count; k++)
+                    dirtyobj.PostNetworkVariableWrite();
-                        {
-                            sobj.ChildNetworkBehaviours[k].PostNetworkVariableWrite();
-                        }
-                    }
                 }
+                m_DirtyNetworkObjects.Clear();
             }
             finally
             {

Runtime/Core/NetworkManager.cs

@@ -20,7 +20,7 @@ namespace Unity.Netcode
     /// <summary>
     /// The main component of the library
     /// </summary>
-    [AddComponentMenu("Netcode/" + nameof(NetworkManager), -100)]
+    [AddComponentMenu("Netcode/Network Manager", -100)]
     public class NetworkManager : MonoBehaviour, INetworkUpdateSystem
     {
 #pragma warning disable IDE1006 // disable naming rule violation check
@@ -51,10 +51,15 @@ namespace Unity.Netcode
 
         internal static string PrefabDebugHelper(NetworkPrefab networkPrefab)
         {
-            return $"{nameof(NetworkPrefab)} \"{networkPrefab.Prefab.gameObject.name}\"";
+            return $"{nameof(NetworkPrefab)} \"{networkPrefab.Prefab.name}\"";
         }
 
-        internal NetworkBehaviourUpdater BehaviourUpdater { get; private set; }
+        internal NetworkBehaviourUpdater BehaviourUpdater { get; set; }
+
+        internal void MarkNetworkObjectDirty(NetworkObject networkObject)
+        {
+            BehaviourUpdater.AddForUpdate(networkObject);
+        }
 
         internal MessagingSystem MessagingSystem { get; private set; }
 
@@ -62,6 +67,9 @@ namespace Unity.Netcode
 
         internal Dictionary<ulong, ConnectionApprovalResponse> ClientsToApprove = new Dictionary<ulong, ConnectionApprovalResponse>();
 
+        /// <summary>
+        /// The <see cref="NetworkPrefabHandler"/> instance created after starting the <see cref="NetworkManager"/>
+        /// </summary>
         public NetworkPrefabHandler PrefabHandler
         {
             get
@@ -78,6 +86,12 @@ namespace Unity.Netcode
         private bool m_ShuttingDown;
         private bool m_StopProcessingMessages;
 
+        /// <summary>
+        /// When disconnected from the server, the server may send a reason. If a reason was sent, this property will
+        /// tell client code what the reason was. It should be queried after the OnClientDisconnectCallback is called
+        /// </summary>
+        public string DisconnectReason { get; internal set; }
+
         private class NetworkManagerHooks : INetworkHooks
         {
             private NetworkManager m_NetworkManager;
@@ -179,8 +193,7 @@ namespace Unity.Netcode
         /// <returns>a <see cref="GameObject"/> that is either the override or if no overrides exist it returns the same as the one passed in as a parameter</returns>
         public GameObject GetNetworkPrefabOverride(GameObject gameObject)
         {
-            var networkObject = gameObject.GetComponent<NetworkObject>();
+            if (gameObject.TryGetComponent<NetworkObject>(out var networkObject))
-            if (networkObject != null)
             {
                 if (NetworkConfig.NetworkPrefabOverrideLinks.ContainsKey(networkObject.GlobalObjectIdHash))
                 {
@@ -197,12 +210,25 @@ namespace Unity.Netcode
             return gameObject;
         }
 
+        /// <summary>
+        /// Accessor for the <see cref="NetworkTimeSystem"/> of the NetworkManager.
+        /// Prefer the use of the LocalTime and ServerTime properties
+        /// </summary>
         public NetworkTimeSystem NetworkTimeSystem { get; private set; }
 
+        /// <summary>
+        /// Accessor for the <see cref="NetworkTickSystem"/> of the NetworkManager.
+        /// </summary>
         public NetworkTickSystem NetworkTickSystem { get; private set; }
 
+        /// <summary>
+        /// The local <see cref="NetworkTime"/>
+        /// </summary>
         public NetworkTime LocalTime => NetworkTickSystem?.LocalTime ?? default;
 
+        /// <summary>
+        /// The <see cref="NetworkTime"/> on the server
+        /// </summary>
         public NetworkTime ServerTime => NetworkTickSystem?.ServerTime ?? default;
 
         /// <summary>
@@ -229,10 +255,19 @@ namespace Unity.Netcode
 
         internal IDeferredMessageManager DeferredMessageManager { get; private set; }
 
+        /// <summary>
+        /// Gets the CustomMessagingManager for this NetworkManager
+        /// </summary>
         public CustomMessagingManager CustomMessagingManager { get; private set; }
 
+        /// <summary>
+        /// The <see cref="NetworkSceneManager"/> instance created after starting the <see cref="NetworkManager"/>
+        /// </summary>
         public NetworkSceneManager SceneManager { get; private set; }
 
+        /// <summary>
+        /// The client id used to represent the server
+        /// </summary>
         public const ulong ServerClientId = 0;
 
         /// <summary>
@@ -337,11 +372,25 @@ namespace Unity.Netcode
         public bool IsListening { get; internal set; }
 
         /// <summary>
-        /// Gets if we are connected as a client
+        /// When true, the client is connected, approved, and synchronized with
+        /// the server.
         /// </summary>
         public bool IsConnectedClient { get; internal set; }
 
+        /// <summary>
+        /// Is true when the client has been approved.
+        /// </summary>
+        /// <remarks>
+        /// This only reflects the client's approved status and does not mean the client
+        /// has finished the connection and synchronization process. The server-host will
+        /// always be approved upon being starting the <see cref="NetworkManager"/>
+        /// <see cref="IsConnectedClient"/>
+        /// </remarks>
+        public bool IsApproved { get; internal set; }
 
+        /// <summary>
+        /// Can be used to determine if the <see cref="NetworkManager"/> is currently shutting itself down
+        /// </summary>
         public bool ShutdownInProgress { get { return m_ShuttingDown; } }
 
         /// <summary>
@@ -374,30 +423,52 @@ namespace Unity.Netcode
         /// <summary>
         /// Connection Approval Response
         /// </summary>
-        /// <param name="Approved">Whether or not the client was approved</param>
-        /// <param name="CreatePlayerObject">If true, a player object will be created. Otherwise the client will have no object.</param>
-        /// <param name="PlayerPrefabHash">The prefabHash to use for the client. If createPlayerObject is false, this is ignored. If playerPrefabHash is null, the default player prefab is used.</param>
-        /// <param name="Position">The position to spawn the client at. If null, the prefab position is used.</param>
-        /// <param name="Rotation">The rotation to spawn the client with. If null, the prefab position is used.</param>
-        /// <param name="Pending">If the Approval decision cannot be made immediately, the client code can set Pending to true, keep a reference to the ConnectionApprovalResponse object and write to it later. Client code must exercise care to setting all the members to the value it wants before marking Pending to false, to indicate completion. If the field is set as Pending = true, we'll monitor the object until it gets set to not pending anymore and use the parameters then.</param>
         public class ConnectionApprovalResponse
         {
+            /// <summary>
+            /// Whether or not the client was approved
+            /// </summary>
             public bool Approved;
+            /// <summary>
+            /// If true, a player object will be created. Otherwise the client will have no object.
+            /// </summary>
             public bool CreatePlayerObject;
+            /// <summary>
+            /// The prefabHash to use for the client. If createPlayerObject is false, this is ignored. If playerPrefabHash is null, the default player prefab is used.
+            /// </summary>
             public uint? PlayerPrefabHash;
+            /// <summary>
+            /// The position to spawn the client at. If null, the prefab position is used.
+            /// </summary>
             public Vector3? Position;
+            /// <summary>
+            /// The rotation to spawn the client with. If null, the prefab position is used.
+            /// </summary>
             public Quaternion? Rotation;
+            /// <summary>
+            /// If the Approval decision cannot be made immediately, the client code can set Pending to true, keep a reference to the ConnectionApprovalResponse object and write to it later. Client code must exercise care to setting all the members to the value it wants before marking Pending to false, to indicate completion. If the field is set as Pending = true, we'll monitor the object until it gets set to not pending anymore and use the parameters then.
+            /// </summary>
             public bool Pending;
+
+            /// <summary>
+            /// Optional reason. If Approved is false, this reason will be sent to the client so they know why they
+            /// were not approved.
+            /// </summary>
+            public string Reason;
         }
 
         /// <summary>
         /// Connection Approval Request
         /// </summary>
-        /// <param name="Payload">The connection data payload</param>
-        /// <param name="ClientNetworkId">The Network Id of the client we are about to handle</param>
         public struct ConnectionApprovalRequest
         {
+            /// <summary>
+            /// The connection data payload
+            /// </summary>
             public byte[] Payload;
+            /// <summary>
+            /// The Network Id of the client we are about to handle
+            /// </summary>
             public ulong ClientNetworkId;
         }
 
@@ -471,8 +542,7 @@ namespace Unity.Netcode
                 var networkPrefabGo = networkPrefab?.Prefab;
                 if (networkPrefabGo != null)
                 {
-                    var networkObject = networkPrefabGo.GetComponent<NetworkObject>();
+                    if (!networkPrefabGo.TryGetComponent<NetworkObject>(out var networkObject))
-                    if (networkObject == null)
                     {
                         if (NetworkLog.CurrentLogLevel <= LogLevel.Normal)
                         {
@@ -647,8 +717,7 @@ namespace Unity.Netcode
             }
             else if (networkPrefab.Override == NetworkPrefabOverride.None)
             {
-                networkObject = networkPrefab.Prefab.GetComponent<NetworkObject>();
+                if (!networkPrefab.Prefab.TryGetComponent(out networkObject))
-                if (networkObject == null)
                 {
                     if (NetworkLog.CurrentLogLevel <= LogLevel.Error)
                     {
@@ -694,8 +763,7 @@ namespace Unity.Netcode
                             }
                             else
                             {
-                                networkObject = networkPrefab.SourcePrefabToOverride.GetComponent<NetworkObject>();
+                                if (!networkPrefab.SourcePrefabToOverride.TryGetComponent(out networkObject))
-                                if (networkObject == null)
                                 {
                                     if (NetworkLog.CurrentLogLevel <= LogLevel.Error)
                                     {
@@ -833,6 +901,9 @@ namespace Unity.Netcode
                 return;
             }
 
+            DisconnectReason = string.Empty;
+            IsApproved = false;
+
             ComponentFactory.SetDefaults();
 
             if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
@@ -920,8 +991,7 @@ namespace Unity.Netcode
             // If we have a player prefab, then we need to verify it is in the list of NetworkPrefabOverrideLinks for client side spawning.
             if (NetworkConfig.PlayerPrefab != null)
             {
-                var playerPrefabNetworkObject = NetworkConfig.PlayerPrefab.GetComponent<NetworkObject>();
+                if (NetworkConfig.PlayerPrefab.TryGetComponent<NetworkObject>(out var playerPrefabNetworkObject))
-                if (playerPrefabNetworkObject != null)
                 {
                     //In the event there is no NetworkPrefab entry (i.e. no override for default player prefab)
                     if (!NetworkConfig.NetworkPrefabOverrideLinks.ContainsKey(playerPrefabNetworkObject
@@ -961,6 +1031,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Starts a server
         /// </summary>
+        /// <returns>(<see cref="true"/>/<see cref="false"/>) returns true if <see cref="NetworkManager"/> started in server mode successfully.</returns>
         public bool StartServer()
         {
             if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
@@ -974,25 +1045,39 @@ namespace Unity.Netcode
             }
 
             Initialize(true);
-
-            // If we failed to start then shutdown and notify user that the transport failed to start
-            if (NetworkConfig.NetworkTransport.StartServer())
-            {
             IsServer = true;
             IsClient = false;
             IsListening = true;
 
+            try
+            {
+                // If we failed to start then shutdown and notify user that the transport failed to start
+                if (NetworkConfig.NetworkTransport.StartServer())
+                {
                     SpawnManager.ServerSpawnSceneObjectsOnStartSweep();
 
                     OnServerStarted?.Invoke();
+                    IsApproved = true;
                     return true;
                 }
                 else
                 {
+                    IsServer = false;
+                    IsClient = false;
+                    IsListening = false;
+
                     Debug.LogError($"Server is shutting down due to network transport start failure of {NetworkConfig.NetworkTransport.GetType().Name}!");
                     OnTransportFailure?.Invoke();
                     Shutdown();
                 }
+            }
+            catch (Exception)
+            {
+                IsServer = false;
+                IsClient = false;
+                IsListening = false;
+                throw;
+            }
 
             return false;
         }
@@ -1000,6 +1085,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Starts a client
         /// </summary>
+        /// <returns>(<see cref="true"/>/<see cref="false"/>) returns true if <see cref="NetworkManager"/> started in client mode successfully.</returns>
         public bool StartClient()
         {
             if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
@@ -1033,6 +1119,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Starts a Host
         /// </summary>
+        /// <returns>(<see cref="true"/>/<see cref="false"/>) returns true if <see cref="NetworkManager"/> started in host mode successfully.</returns>
         public bool StartHost()
         {
             if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
@@ -1047,23 +1134,38 @@ namespace Unity.Netcode
 
             Initialize(true);
 
+            IsServer = true;
+            IsClient = true;
+            IsListening = true;
+
+            try
+            {
                 // If we failed to start then shutdown and notify user that the transport failed to start
                 if (!NetworkConfig.NetworkTransport.StartServer())
                 {
                     Debug.LogError($"Server is shutting down due to network transport start failure of {NetworkConfig.NetworkTransport.GetType().Name}!");
                     OnTransportFailure?.Invoke();
                     Shutdown();
+
+                    IsServer = false;
+                    IsClient = false;
+                    IsListening = false;
+
                     return false;
                 }
+            }
+            catch (Exception)
+            {
+                IsServer = false;
+                IsClient = false;
+                IsListening = false;
+                throw;
+            }
 
             MessagingSystem.ClientConnected(ServerClientId);
             LocalClientId = ServerClientId;
             NetworkMetrics.SetConnectionId(LocalClientId);
 
-            IsServer = true;
-            IsClient = true;
-            IsListening = true;
-
             if (NetworkConfig.ConnectionApproval && ConnectionApprovalCallback != null)
             {
                 var response = new ConnectionApprovalResponse();
@@ -1077,6 +1179,7 @@ namespace Unity.Netcode
                 }
 
                 response.Approved = true;
+                IsApproved = true;
                 HandleConnectionApproval(ServerClientId, response);
             }
             else
@@ -1091,6 +1194,11 @@ namespace Unity.Netcode
 
             SpawnManager.ServerSpawnSceneObjectsOnStartSweep();
 
+            // This assures that any in-scene placed NetworkObject is spawned and
+            // any associated NetworkBehaviours' netcode related properties are
+            // set prior to invoking OnClientConnected.
+            InvokeOnClientConnectedCallback(LocalClientId);
+
             OnServerStarted?.Invoke();
 
             return true;
@@ -1144,6 +1252,9 @@ namespace Unity.Netcode
             return true;
         }
 
+        /// <summary>
+        /// Set this NetworkManager instance as the static NetworkManager singleton
+        /// </summary>
         public void SetSingleton()
         {
             Singleton = this;
@@ -1248,6 +1359,7 @@ namespace Unity.Netcode
         private void DisconnectRemoteClient(ulong clientId)
         {
             var transportId = ClientIdToTransportId(clientId);
+            MessagingSystem.ProcessSendQueues();
             NetworkConfig.NetworkTransport.DisconnectRemoteClient(transportId);
         }
 
@@ -1328,13 +1440,27 @@ namespace Unity.Netcode
                 }
             }
 
-            if (IsClient && IsConnectedClient)
+            if (IsClient && IsListening)
             {
                 // Client only, send disconnect to server
                 NetworkConfig.NetworkTransport.DisconnectLocalClient();
             }
 
             IsConnectedClient = false;
+            IsApproved = false;
+
+            // We need to clean up NetworkObjects before we reset the IsServer
+            // and IsClient properties. This provides consistency of these two
+            // property values for NetworkObjects that are still spawned when
+            // the shutdown cycle begins.
+            if (SpawnManager != null)
+            {
+                SpawnManager.DespawnAndDestroyNetworkObjects();
+                SpawnManager.ServerResetShudownStateForSceneObjects();
+
+                SpawnManager = null;
+            }
+
             IsServer = false;
             IsClient = false;
 
@@ -1357,14 +1483,6 @@ namespace Unity.Netcode
                 NetworkConfig.NetworkTransport.OnTransportEvent -= HandleRawTransportPoll;
             }
 
-            if (SpawnManager != null)
-            {
-                SpawnManager.DespawnAndDestroyNetworkObjects();
-                SpawnManager.ServerResetShudownStateForSceneObjects();
-
-                SpawnManager = null;
-            }
-
             if (DeferredMessageManager != null)
             {
                 DeferredMessageManager.CleanupAllTriggers();
@@ -1405,7 +1523,7 @@ namespace Unity.Netcode
             ClearClients();
         }
 
-        // INetworkUpdateSystem
+        /// <inheritdoc />
         public void NetworkUpdate(NetworkUpdateStage updateStage)
         {
             switch (updateStage)
@@ -1480,6 +1598,7 @@ namespace Unity.Netcode
             } while (IsListening && networkEvent != NetworkEvent.Nothing);
 
             MessagingSystem.ProcessIncomingMessageQueue();
+            MessagingSystem.CleanupDisconnectedClients();
 
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
             s_TransportPoll.End();
@@ -1501,7 +1620,7 @@ namespace Unity.Netcode
             }
 
             // Only update RTT here, server time is updated by time sync messages
-            var reset = NetworkTimeSystem.Advance(Time.deltaTime);
+            var reset = NetworkTimeSystem.Advance(Time.unscaledDeltaTime);
             if (reset)
             {
                 NetworkTickSystem.Reset(NetworkTimeSystem.LocalTime, NetworkTimeSystem.ServerTime);
@@ -1510,7 +1629,7 @@ namespace Unity.Netcode
 
             if (IsServer == false)
             {
-                NetworkTimeSystem.Sync(NetworkTimeSystem.LastSyncedServerTimeSec + Time.deltaTime, NetworkConfig.NetworkTransport.GetCurrentRtt(ServerClientId) / 1000d);
+                NetworkTimeSystem.Sync(NetworkTimeSystem.LastSyncedServerTimeSec + Time.unscaledDeltaTime, NetworkConfig.NetworkTransport.GetCurrentRtt(ServerClientId) / 1000d);
             }
         }
 
@@ -1555,33 +1674,101 @@ namespace Unity.Netcode
         {
             var message = new ConnectionRequestMessage
             {
-                ConfigHash = NetworkConfig.GetConfig(),
+                // Since only a remote client will send a connection request,
+                // we should always force the rebuilding of the NetworkConfig hash value
+                ConfigHash = NetworkConfig.GetConfig(false),
                 ShouldSendConnectionData = NetworkConfig.ConnectionApproval,
                 ConnectionData = NetworkConfig.ConnectionData
             };
+
+            message.MessageVersions = new NativeArray<MessageVersionData>(MessagingSystem.MessageHandlers.Length, Allocator.Temp);
+            for (int index = 0; index < MessagingSystem.MessageHandlers.Length; index++)
+            {
+                if (MessagingSystem.MessageTypes[index] != null)
+                {
+                    var type = MessagingSystem.MessageTypes[index];
+                    message.MessageVersions[index] = new MessageVersionData
+                    {
+                        Hash = XXHash.Hash32(type.FullName),
+                        Version = MessagingSystem.GetLocalVersion(type)
+                    };
+                }
+            }
+
             SendMessage(ref message, NetworkDelivery.ReliableSequenced, ServerClientId);
+            message.MessageVersions.Dispose();
         }
 
         private IEnumerator ApprovalTimeout(ulong clientId)
         {
-            NetworkTime timeStarted = LocalTime;
+            var timeStarted = IsServer ? LocalTime.TimeAsFloat : Time.realtimeSinceStartup;
+            var timedOut = false;
+            var connectionApproved = false;
+            var connectionNotApproved = false;
+            var timeoutMarker = timeStarted + NetworkConfig.ClientConnectionBufferTimeout;
 
-            //We yield every frame incase a pending client disconnects and someone else gets its connection id
+            while (IsListening && !ShutdownInProgress && !timedOut && !connectionApproved)
-            while ((LocalTime - timeStarted).Time < NetworkConfig.ClientConnectionBufferTimeout && PendingClients.ContainsKey(clientId))
             {
                 yield return null;
+                // Check if we timed out
+                timedOut = timeoutMarker < (IsServer ? LocalTime.TimeAsFloat : Time.realtimeSinceStartup);
+
+                if (IsServer)
+                {
+                    // When the client is no longer in the pending clients list and is in the connected clients list
+                    // it has been approved
+                    connectionApproved = !PendingClients.ContainsKey(clientId) && ConnectedClients.ContainsKey(clientId);
+
+                    // For the server side, if the client is in neither list then it was declined or the client disconnected
+                    connectionNotApproved = !PendingClients.ContainsKey(clientId) && !ConnectedClients.ContainsKey(clientId);
+                }
+                else
+                {
+                    connectionApproved = IsApproved;
+                }
             }
 
-            if (PendingClients.ContainsKey(clientId) && !ConnectedClients.ContainsKey(clientId))
+            // Exit coroutine if we are no longer listening or a shutdown is in progress (client or server)
+            if (!IsListening || ShutdownInProgress)
+            {
+                yield break;
+            }
+
+            // If the client timed out or was not approved
+            if (timedOut || connectionNotApproved)
             {
                 // Timeout
                 if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
                 {
-                    NetworkLog.LogInfo($"Client {clientId} Handshake Timed Out");
+                    if (timedOut)
+                    {
+                        if (IsServer)
+                        {
+                            // Log a warning that the transport detected a connection but then did not receive a follow up connection request message.
+                            // (hacking or something happened to the server's network connection)
+                            NetworkLog.LogWarning($"Server detected a transport connection from Client-{clientId}, but timed out waiting for the connection request message.");
+                        }
+                        else
+                        {
+                            // We only provide informational logging for the client side
+                            NetworkLog.LogInfo("Timed out waiting for the server to approve the connection request.");
+                        }
+                    }
+                    else if (connectionNotApproved)
+                    {
+                        NetworkLog.LogInfo($"Client-{clientId} was either denied approval or disconnected while being approved.");
+                    }
                 }
 
+                if (IsServer)
+                {
                     DisconnectClient(clientId);
                 }
+                else
+                {
+                    Shutdown(true);
+                }
+            }
         }
 
         internal ulong TransportIdToClientId(ulong transportId)
@@ -1670,7 +1857,18 @@ namespace Unity.Netcode
                         NetworkLog.LogInfo($"Disconnect Event From {clientId}");
                     }
 
+                    // Process the incoming message queue so that we get everything from the server disconnecting us
+                    // or, if we are the server, so we got everything from that client.
+                    MessagingSystem.ProcessIncomingMessageQueue();
+
+                    try
+                    {
                         OnClientDisconnectCallback?.Invoke(clientId);
+                    }
+                    catch (Exception exception)
+                    {
+                        Debug.LogException(exception);
+                    }
 
                     if (IsServer)
                     {
@@ -1836,12 +2034,31 @@ namespace Unity.Netcode
         /// </summary>
         /// <param name="clientId">The ClientId to disconnect</param>
         public void DisconnectClient(ulong clientId)
+        {
+            DisconnectClient(clientId, null);
+        }
+
+        /// <summary>
+        /// Disconnects the remote client.
+        /// </summary>
+        /// <param name="clientId">The ClientId to disconnect</param>
+        /// <param name="reason">Disconnection reason. If set, client will receive a DisconnectReasonMessage and have the
+        /// reason available in the NetworkManager.DisconnectReason property</param>
+        public void DisconnectClient(ulong clientId, string reason)
         {
             if (!IsServer)
             {
                 throw new NotServerException($"Only server can disconnect remote clients. Please use `{nameof(Shutdown)}()` instead.");
             }
 
+            if (!string.IsNullOrEmpty(reason))
+            {
+                var disconnectReason = new DisconnectReasonMessage();
+                disconnectReason.Reason = reason;
+                SendMessage(ref disconnectReason, NetworkDelivery.Reliable, clientId);
+            }
+            MessagingSystem.ProcessSendQueues();
+
             OnClientDisconnectFromServer(clientId);
             DisconnectRemoteClient(clientId);
         }
@@ -1856,6 +2073,8 @@ namespace Unity.Netcode
                 {
                     var playerObject = networkClient.PlayerObject;
                     if (playerObject != null)
+                    {
+                        if (!playerObject.DontDestroyWithOwner)
                         {
                             if (PrefabHandler.ContainsHandler(ConnectedClients[clientId].PlayerObject.GlobalObjectIdHash))
                             {
@@ -1866,6 +2085,11 @@ namespace Unity.Netcode
                                 Destroy(playerObject.gameObject);
                             }
                         }
+                        else
+                        {
+                            playerObject.RemoveOwnership();
+                        }
+                    }
 
                     // Get the NetworkObjects owned by the disconnected client
                     var clientOwnedObjects = SpawnManager.GetClientOwnedObjects(clientId);
@@ -1974,14 +2198,28 @@ namespace Unity.Netcode
 
                 if (response.CreatePlayerObject)
                 {
-                    var networkObject = SpawnManager.CreateLocalNetworkObject(
+                    var playerPrefabHash = response.PlayerPrefabHash ?? NetworkConfig.PlayerPrefab.GetComponent<NetworkObject>().GlobalObjectIdHash;
-                        isSceneObject: false,
+
-                        response.PlayerPrefabHash ?? NetworkConfig.PlayerPrefab.GetComponent<NetworkObject>().GlobalObjectIdHash,
+                    // Generate a SceneObject for the player object to spawn
-                        ownerClientId,
+                    var sceneObject = new NetworkObject.SceneObject
-                        parentNetworkId: null,
+                    {
-                        networkSceneHandle: null,
+                        OwnerClientId = ownerClientId,
-                        response.Position,
+                        IsPlayerObject = true,
-                        response.Rotation);
+                        IsSceneObject = false,
+                        HasTransform = true,
+                        Hash = playerPrefabHash,
+                        TargetClientId = ownerClientId,
+                        Transform = new NetworkObject.SceneObject.TransformData
+                        {
+                            Position = response.Position.GetValueOrDefault(),
+                            Rotation = response.Rotation.GetValueOrDefault()
+                        }
+                    };
+
+                    // Create the player NetworkObject locally
+                    var networkObject = SpawnManager.CreateLocalNetworkObject(sceneObject);
+
+                    // Spawn the player NetworkObject locally
                     SpawnManager.SpawnNetworkObjectLocally(
                         networkObject,
                         SpawnManager.GetNetworkObjectId(),
@@ -2009,7 +2247,22 @@ namespace Unity.Netcode
                         }
                     }
 
+                    message.MessageVersions = new NativeArray<MessageVersionData>(MessagingSystem.MessageHandlers.Length, Allocator.Temp);
+                    for (int index = 0; index < MessagingSystem.MessageHandlers.Length; index++)
+                    {
+                        if (MessagingSystem.MessageTypes[index] != null)
+                        {
+                            var type = MessagingSystem.MessageTypes[index];
+                            message.MessageVersions[index] = new MessageVersionData
+                            {
+                                Hash = XXHash.Hash32(type.FullName),
+                                Version = MessagingSystem.GetLocalVersion(type)
+                            };
+                        }
+                    }
+
                     SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, ownerClientId);
+                    message.MessageVersions.Dispose();
 
                     // If scene management is enabled, then let NetworkSceneManager handle the initial scene and NetworkObject synchronization
                     if (!NetworkConfig.EnableSceneManagement)
@@ -2025,7 +2278,6 @@ namespace Unity.Netcode
                 {
                     LocalClient = client;
                     SpawnManager.UpdateObservedNetworkObjects(ownerClientId);
-                    InvokeOnClientConnectedCallback(ownerClientId);
                 }
 
                 if (!response.CreatePlayerObject || (response.PlayerPrefabHash == null && NetworkConfig.PlayerPrefab == null))
@@ -2038,6 +2290,15 @@ namespace Unity.Netcode
             }
             else
             {
+                if (!string.IsNullOrEmpty(response.Reason))
+                {
+                    var disconnectReason = new DisconnectReasonMessage();
+                    disconnectReason.Reason = response.Reason;
+                    SendMessage(ref disconnectReason, NetworkDelivery.Reliable, ownerClientId);
+
+                    MessagingSystem.ProcessSendQueues();
+                }
+
                 PendingClients.Remove(ownerClientId);
                 DisconnectRemoteClient(ownerClientId);
             }
@@ -2064,11 +2325,11 @@ namespace Unity.Netcode
                 {
                     ObjectInfo = ConnectedClients[clientId].PlayerObject.GetMessageSceneObject(clientPair.Key)
                 };
-                message.ObjectInfo.Header.Hash = playerPrefabHash;
+                message.ObjectInfo.Hash = playerPrefabHash;
-                message.ObjectInfo.Header.IsSceneObject = false;
+                message.ObjectInfo.IsSceneObject = false;
-                message.ObjectInfo.Header.HasParent = false;
+                message.ObjectInfo.HasParent = false;
-                message.ObjectInfo.Header.IsPlayerObject = true;
+                message.ObjectInfo.IsPlayerObject = true;
-                message.ObjectInfo.Header.OwnerClientId = clientId;
+                message.ObjectInfo.OwnerClientId = clientId;
                 var size = SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, clientPair.Key);
                 NetworkMetrics.TrackObjectSpawnSent(clientPair.Key, ConnectedClients[clientId].PlayerObject, size);
             }

Runtime/Core/NetworkUpdateLoop.cs

@@ -7,25 +7,55 @@ using UnityEngine.PlayerLoop;
 namespace Unity.Netcode
 {
     /// <summary>
-    /// Defines the required interface of a network update system being executed by the network update loop.
+    /// Defines the required interface of a network update system being executed by the <see cref="NetworkUpdateLoop"/>.
     /// </summary>
     public interface INetworkUpdateSystem
     {
+        /// <summary>
+        /// The update method that is being executed in the context of related <see cref="NetworkUpdateStage"/>.
+        /// </summary>
+        /// <param name="updateStage">The <see cref="NetworkUpdateStage"/> that is being executed.</param>
         void NetworkUpdate(NetworkUpdateStage updateStage);
     }
 
     /// <summary>
     /// Defines network update stages being executed by the network update loop.
+    /// See for more details on update stages:
+    /// https://docs.unity3d.com/ScriptReference/PlayerLoop.Initialization.html
     /// </summary>
     public enum NetworkUpdateStage : byte
     {
-        Unset = 0, // Default
+        /// <summary>
+        /// Default value
+        /// </summary>
+        Unset = 0,
+        /// <summary>
+        /// Very first initialization update
+        /// </summary>
         Initialization = 1,
+        /// <summary>
+        /// Invoked before Fixed update
+        /// </summary>
         EarlyUpdate = 2,
+        /// <summary>
+        /// Fixed Update (i.e. state machine, physics, animations, etc)
+        /// </summary>
         FixedUpdate = 3,
+        /// <summary>
+        /// Updated before the Monobehaviour.Update for all components is invoked
+        /// </summary>
         PreUpdate = 4,
+        /// <summary>
+        /// Updated when the Monobehaviour.Update for all components is invoked
+        /// </summary>
         Update = 5,
+        /// <summary>
+        /// Updated before the Monobehaviour.LateUpdate for all components is invoked
+        /// </summary>
         PreLateUpdate = 6,
+        /// <summary>
+        /// Updated after the Monobehaviour.LateUpdate for all components is invoked
+        /// </summary>
         PostLateUpdate = 7
     }
 
@@ -53,6 +83,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Registers a network update system to be executed in all network update stages.
         /// </summary>
+        /// <param name="updateSystem">The <see cref="INetworkUpdateSystem"/> implementation to register for all network updates</param>
         public static void RegisterAllNetworkUpdates(this INetworkUpdateSystem updateSystem)
         {
             foreach (NetworkUpdateStage updateStage in Enum.GetValues(typeof(NetworkUpdateStage)))
@@ -64,6 +95,8 @@ namespace Unity.Netcode
         /// <summary>
         /// Registers a network update system to be executed in a specific network update stage.
         /// </summary>
+        /// <param name="updateSystem">The <see cref="INetworkUpdateSystem"/> implementation to register for all network updates</param>
+        /// <param name="updateStage">The <see cref="NetworkUpdateStage"/> being registered for the <see cref="INetworkUpdateSystem"/> implementation</param>
         public static void RegisterNetworkUpdate(this INetworkUpdateSystem updateSystem, NetworkUpdateStage updateStage = NetworkUpdateStage.Update)
         {
             var sysSet = s_UpdateSystem_Sets[updateStage];
@@ -94,6 +127,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Unregisters a network update system from all network update stages.
         /// </summary>
+        /// <param name="updateSystem">The <see cref="INetworkUpdateSystem"/> implementation to deregister from all network updates</param>
         public static void UnregisterAllNetworkUpdates(this INetworkUpdateSystem updateSystem)
         {
             foreach (NetworkUpdateStage updateStage in Enum.GetValues(typeof(NetworkUpdateStage)))
@@ -105,6 +139,8 @@ namespace Unity.Netcode
         /// <summary>
         /// Unregisters a network update system from a specific network update stage.
         /// </summary>
+        /// <param name="updateSystem">The <see cref="INetworkUpdateSystem"/> implementation to deregister from all network updates</param>
+        /// <param name="updateStage">The <see cref="NetworkUpdateStage"/> to be deregistered from the <see cref="INetworkUpdateSystem"/> implementation</param>
         public static void UnregisterNetworkUpdate(this INetworkUpdateSystem updateSystem, NetworkUpdateStage updateStage = NetworkUpdateStage.Update)
         {
             var sysSet = s_UpdateSystem_Sets[updateStage];

Runtime/Exceptions/InvalidParentException.cs

@@ -7,8 +7,18 @@ namespace Unity.Netcode
     /// </summary>
     public class InvalidParentException : Exception
     {
+        /// <summary>
+        /// Constructor for <see cref="InvalidParentException"/>
+        /// </summary>
         public InvalidParentException() { }
+
+        /// <inheritdoc/>
+        /// <param name="message"></param>
         public InvalidParentException(string message) : base(message) { }
+
+        /// <inheritdoc/>
+        /// <param name="message"></param>
+        /// <param name="innerException"></param>
         public InvalidParentException(string message, Exception innerException) : base(message, innerException) { }
     }
 }

Runtime/Exceptions/SpawnStateException.cs

@@ -26,8 +26,15 @@ namespace Unity.Netcode
         public SpawnStateException(string message, Exception inner) : base(message, inner) { }
     }
 
+    /// <summary>
+    /// Exception thrown when a specified network channel is invalid
+    /// </summary>
     public class InvalidChannelException : Exception
     {
+        /// <summary>
+        /// Constructs an InvalidChannelException with a message
+        /// </summary>
+        /// <param name="message">the message</param>
         public InvalidChannelException(string message) : base(message) { }
     }
 }

Runtime/Hashing/XXHash.cs

@@ -0,0 +1,248 @@
+using System;
+using System.Text;
+using System.Runtime.CompilerServices;
+
+namespace Unity.Netcode
+{
+    internal static class XXHash
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe uint Hash32(byte* input, int length, uint seed = 0)
+        {
+            unchecked
+            {
+                const uint prime1 = 2654435761u;
+                const uint prime2 = 2246822519u;
+                const uint prime3 = 3266489917u;
+                const uint prime4 = 0668265263u;
+                const uint prime5 = 0374761393u;
+
+                uint hash = seed + prime5;
+
+                if (length >= 16)
+                {
+                    uint val0 = seed + prime1 + prime2;
+                    uint val1 = seed + prime2;
+                    uint val2 = seed + 0;
+                    uint val3 = seed - prime1;
+
+                    int count = length >> 4;
+                    for (int i = 0; i < count; i++)
+                    {
+                        var pos0 = *(uint*)(input + 0);
+                        var pos1 = *(uint*)(input + 4);
+                        var pos2 = *(uint*)(input + 8);
+                        var pos3 = *(uint*)(input + 12);
+
+                        val0 += pos0 * prime2;
+                        val0 = (val0 << 13) | (val0 >> (32 - 13));
+                        val0 *= prime1;
+
+                        val1 += pos1 * prime2;
+                        val1 = (val1 << 13) | (val1 >> (32 - 13));
+                        val1 *= prime1;
+
+                        val2 += pos2 * prime2;
+                        val2 = (val2 << 13) | (val2 >> (32 - 13));
+                        val2 *= prime1;
+
+                        val3 += pos3 * prime2;
+                        val3 = (val3 << 13) | (val3 >> (32 - 13));
+                        val3 *= prime1;
+
+                        input += 16;
+                    }
+
+                    hash = ((val0 << 01) | (val0 >> (32 - 01))) +
+                           ((val1 << 07) | (val1 >> (32 - 07))) +
+                           ((val2 << 12) | (val2 >> (32 - 12))) +
+                           ((val3 << 18) | (val3 >> (32 - 18)));
+                }
+
+                hash += (uint)length;
+
+                length &= 15;
+                while (length >= 4)
+                {
+                    hash += *(uint*)input * prime3;
+                    hash = ((hash << 17) | (hash >> (32 - 17))) * prime4;
+                    input += 4;
+                    length -= 4;
+                }
+                while (length > 0)
+                {
+                    hash += *input * prime5;
+                    hash = ((hash << 11) | (hash >> (32 - 11))) * prime1;
+                    ++input;
+                    --length;
+                }
+
+                hash ^= hash >> 15;
+                hash *= prime2;
+                hash ^= hash >> 13;
+                hash *= prime3;
+                hash ^= hash >> 16;
+
+                return hash;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe ulong Hash64(byte* input, int length, uint seed = 0)
+        {
+            unchecked
+            {
+                const ulong prime1 = 11400714785074694791ul;
+                const ulong prime2 = 14029467366897019727ul;
+                const ulong prime3 = 01609587929392839161ul;
+                const ulong prime4 = 09650029242287828579ul;
+                const ulong prime5 = 02870177450012600261ul;
+
+                ulong hash = seed + prime5;
+
+                if (length >= 32)
+                {
+                    ulong val0 = seed + prime1 + prime2;
+                    ulong val1 = seed + prime2;
+                    ulong val2 = seed + 0;
+                    ulong val3 = seed - prime1;
+
+                    int count = length >> 5;
+                    for (int i = 0; i < count; i++)
+                    {
+                        var pos0 = *(ulong*)(input + 0);
+                        var pos1 = *(ulong*)(input + 8);
+                        var pos2 = *(ulong*)(input + 16);
+                        var pos3 = *(ulong*)(input + 24);
+
+                        val0 += pos0 * prime2;
+                        val0 = (val0 << 31) | (val0 >> (64 - 31));
+                        val0 *= prime1;
+
+                        val1 += pos1 * prime2;
+                        val1 = (val1 << 31) | (val1 >> (64 - 31));
+                        val1 *= prime1;
+
+                        val2 += pos2 * prime2;
+                        val2 = (val2 << 31) | (val2 >> (64 - 31));
+                        val2 *= prime1;
+
+                        val3 += pos3 * prime2;
+                        val3 = (val3 << 31) | (val3 >> (64 - 31));
+                        val3 *= prime1;
+
+                        input += 32;
+                    }
+
+                    hash = ((val0 << 01) | (val0 >> (64 - 01))) +
+                           ((val1 << 07) | (val1 >> (64 - 07))) +
+                           ((val2 << 12) | (val2 >> (64 - 12))) +
+                           ((val3 << 18) | (val3 >> (64 - 18)));
+
+                    val0 *= prime2;
+                    val0 = (val0 << 31) | (val0 >> (64 - 31));
+                    val0 *= prime1;
+                    hash ^= val0;
+                    hash = hash * prime1 + prime4;
+
+                    val1 *= prime2;
+                    val1 = (val1 << 31) | (val1 >> (64 - 31));
+                    val1 *= prime1;
+                    hash ^= val1;
+                    hash = hash * prime1 + prime4;
+
+                    val2 *= prime2;
+                    val2 = (val2 << 31) | (val2 >> (64 - 31));
+                    val2 *= prime1;
+                    hash ^= val2;
+                    hash = hash * prime1 + prime4;
+
+                    val3 *= prime2;
+                    val3 = (val3 << 31) | (val3 >> (64 - 31));
+                    val3 *= prime1;
+                    hash ^= val3;
+                    hash = hash * prime1 + prime4;
+                }
+
+                hash += (ulong)length;
+
+                length &= 31;
+                while (length >= 8)
+                {
+                    ulong lane = *(ulong*)input * prime2;
+                    lane = ((lane << 31) | (lane >> (64 - 31))) * prime1;
+                    hash ^= lane;
+                    hash = ((hash << 27) | (hash >> (64 - 27))) * prime1 + prime4;
+                    input += 8;
+                    length -= 8;
+                }
+                if (length >= 4)
+                {
+                    hash ^= *(uint*)input * prime1;
+                    hash = ((hash << 23) | (hash >> (64 - 23))) * prime2 + prime3;
+                    input += 4;
+                    length -= 4;
+                }
+                while (length > 0)
+                {
+                    hash ^= *input * prime5;
+                    hash = ((hash << 11) | (hash >> (64 - 11))) * prime1;
+                    ++input;
+                    --length;
+                }
+
+                hash ^= hash >> 33;
+                hash *= prime2;
+                hash ^= hash >> 29;
+                hash *= prime3;
+                hash ^= hash >> 32;
+
+                return hash;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint Hash32(this byte[] buffer)
+        {
+            int length = buffer.Length;
+            unsafe
+            {
+                fixed (byte* pointer = buffer)
+                {
+                    return Hash32(pointer, length);
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint Hash32(this string text) => Hash32(Encoding.UTF8.GetBytes(text));
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint Hash32(this Type type) => Hash32(type.FullName);
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint Hash32<T>() => Hash32(typeof(T));
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ulong Hash64(this byte[] buffer)
+        {
+            int length = buffer.Length;
+            unsafe
+            {
+                fixed (byte* pointer = buffer)
+                {
+                    return Hash64(pointer, length);
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ulong Hash64(this string text) => Hash64(Encoding.UTF8.GetBytes(text));
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ulong Hash64(this Type type) => Hash64(type.FullName);
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ulong Hash64<T>() => Hash64(typeof(T));
+    }
+}

Runtime/Hashing/XXHash.cs.meta

@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: b5aa7a49e9e694f148d810d34577546b
+guid: c3077af091aa443acbdea9d3e97727b0
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2

Runtime/Hashing/XXHash/LICENSE

@@ -1,21 +0,0 @@
-The MIT License (MIT)
-
-Copyright (c) 2015, 2016 Sedat Kapanoglu
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.

Runtime/Hashing/XXHash/LICENSE.meta

@@ -1,7 +0,0 @@
-fileFormatVersion: 2
-guid: cf89ecbf6f9954c8ea6d0848b1e79d87
-DefaultImporter:
-  externalObjects: {}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: 

Runtime/Hashing/XXHash/XXHash.cs

@@ -1,318 +0,0 @@
-// <copyright file="XXHash.cs" company="Sedat Kapanoglu">
-// Copyright (c) 2015-2019 Sedat Kapanoglu
-// MIT License (see LICENSE file for details)
-// </copyright>
-
-// @mfatihmar (Unity): Modified for Unity support
-
-using System.Text;
-using System.Runtime.CompilerServices;
-
-namespace Unity.Netcode
-{
-    /// <summary>
-    /// XXHash implementation.
-    /// </summary>
-    internal static class XXHash
-    {
-        private const ulong k_Prime64v1 = 11400714785074694791ul;
-        private const ulong k_Prime64v2 = 14029467366897019727ul;
-        private const ulong k_Prime64v3 = 1609587929392839161ul;
-        private const ulong k_Prime64v4 = 9650029242287828579ul;
-        private const ulong k_Prime64v5 = 2870177450012600261ul;
-
-        private const uint k_Prime32v1 = 2654435761u;
-        private const uint k_Prime32v2 = 2246822519u;
-        private const uint k_Prime32v3 = 3266489917u;
-        private const uint k_Prime32v4 = 668265263u;
-        private const uint k_Prime32v5 = 374761393u;
-
-        public static uint Hash32(string text) => Hash32(text, Encoding.UTF8);
-        public static uint Hash32(string text, Encoding encoding) => Hash32(encoding.GetBytes(text));
-        public static uint Hash32(byte[] buffer)
-        {
-            unsafe
-            {
-                fixed (byte* ptr = buffer)
-                {
-                    return Hash32(ptr, buffer.Length);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Generate a 32-bit xxHash value.
-        /// </summary>
-        /// <param name="buffer">Input buffer.</param>
-        /// <param name="bufferLength">Input buffer length.</param>
-        /// <param name="seed">Optional seed.</param>
-        /// <returns>32-bit hash value.</returns>
-        public static unsafe uint Hash32(byte* buffer, int bufferLength, uint seed = 0)
-        {
-            const int stripeLength = 16;
-
-            int len = bufferLength;
-            int remainingLen = len;
-            uint acc;
-
-            byte* pInput = buffer;
-            if (len >= stripeLength)
-            {
-                uint acc1 = seed + k_Prime32v1 + k_Prime32v2;
-                uint acc2 = seed + k_Prime32v2;
-                uint acc3 = seed;
-                uint acc4 = seed - k_Prime32v1;
-
-                do
-                {
-                    acc = processStripe32(ref pInput, ref acc1, ref acc2, ref acc3, ref acc4);
-                    remainingLen -= stripeLength;
-                } while (remainingLen >= stripeLength);
-            }
-            else
-            {
-                acc = seed + k_Prime32v5;
-            }
-
-            acc += (uint)len;
-            acc = processRemaining32(pInput, acc, remainingLen);
-
-            return avalanche32(acc);
-        }
-
-        public static ulong Hash64(string text) => Hash64(text, Encoding.UTF8);
-        public static ulong Hash64(string text, Encoding encoding) => Hash64(encoding.GetBytes(text));
-        public static ulong Hash64(byte[] buffer)
-        {
-            unsafe
-            {
-                fixed (byte* ptr = buffer)
-                {
-                    return Hash64(ptr, buffer.Length);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Generate a 64-bit xxHash value.
-        /// </summary>
-        /// <param name="buffer">Input buffer.</param>
-        /// <param name="bufferLength">Input buffer length.</param>
-        /// <param name="seed">Optional seed.</param>
-        /// <returns>Computed 64-bit hash value.</returns>
-        public static unsafe ulong Hash64(byte* buffer, int bufferLength, ulong seed = 0)
-        {
-            const int stripeLength = 32;
-
-            int len = bufferLength;
-            int remainingLen = len;
-            ulong acc;
-
-            byte* pInput = buffer;
-            if (len >= stripeLength)
-            {
-                ulong acc1 = seed + k_Prime64v1 + k_Prime64v2;
-                ulong acc2 = seed + k_Prime64v2;
-                ulong acc3 = seed;
-                ulong acc4 = seed - k_Prime64v1;
-
-                do
-                {
-                    acc = processStripe64(ref pInput, ref acc1, ref acc2, ref acc3, ref acc4);
-                    remainingLen -= stripeLength;
-                } while (remainingLen >= stripeLength);
-            }
-            else
-            {
-                acc = seed + k_Prime64v5;
-            }
-
-            acc += (ulong)len;
-            acc = processRemaining64(pInput, acc, remainingLen);
-
-
-            return avalanche64(acc);
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe ulong processStripe64(
-            ref byte* pInput,
-            ref ulong acc1,
-            ref ulong acc2,
-            ref ulong acc3,
-            ref ulong acc4)
-        {
-            processLane64(ref acc1, ref pInput);
-            processLane64(ref acc2, ref pInput);
-            processLane64(ref acc3, ref pInput);
-            processLane64(ref acc4, ref pInput);
-
-            ulong acc = Bits.RotateLeft(acc1, 1)
-                        + Bits.RotateLeft(acc2, 7)
-                        + Bits.RotateLeft(acc3, 12)
-                        + Bits.RotateLeft(acc4, 18);
-
-            mergeAccumulator64(ref acc, acc1);
-            mergeAccumulator64(ref acc, acc2);
-            mergeAccumulator64(ref acc, acc3);
-            mergeAccumulator64(ref acc, acc4);
-            return acc;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe void processLane64(ref ulong accn, ref byte* pInput)
-        {
-            ulong lane = *(ulong*)pInput;
-            accn = round64(accn, lane);
-            pInput += 8;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe ulong processRemaining64(
-            byte* pInput,
-            ulong acc,
-            int remainingLen)
-        {
-            for (ulong lane; remainingLen >= 8; remainingLen -= 8, pInput += 8)
-            {
-                lane = *(ulong*)pInput;
-
-                acc ^= round64(0, lane);
-                acc = Bits.RotateLeft(acc, 27) * k_Prime64v1;
-                acc += k_Prime64v4;
-            }
-
-            for (uint lane32; remainingLen >= 4; remainingLen -= 4, pInput += 4)
-            {
-                lane32 = *(uint*)pInput;
-
-                acc ^= lane32 * k_Prime64v1;
-                acc = Bits.RotateLeft(acc, 23) * k_Prime64v2;
-                acc += k_Prime64v3;
-            }
-
-            for (byte lane8; remainingLen >= 1; remainingLen--, pInput++)
-            {
-                lane8 = *pInput;
-                acc ^= lane8 * k_Prime64v5;
-                acc = Bits.RotateLeft(acc, 11) * k_Prime64v1;
-            }
-
-            return acc;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static ulong avalanche64(ulong acc)
-        {
-            acc ^= acc >> 33;
-            acc *= k_Prime64v2;
-            acc ^= acc >> 29;
-            acc *= k_Prime64v3;
-            acc ^= acc >> 32;
-            return acc;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static ulong round64(ulong accn, ulong lane)
-        {
-            accn += lane * k_Prime64v2;
-            return Bits.RotateLeft(accn, 31) * k_Prime64v1;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static void mergeAccumulator64(ref ulong acc, ulong accn)
-        {
-            acc ^= round64(0, accn);
-            acc *= k_Prime64v1;
-            acc += k_Prime64v4;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe uint processStripe32(
-            ref byte* pInput,
-            ref uint acc1,
-            ref uint acc2,
-            ref uint acc3,
-            ref uint acc4)
-        {
-            processLane32(ref pInput, ref acc1);
-            processLane32(ref pInput, ref acc2);
-            processLane32(ref pInput, ref acc3);
-            processLane32(ref pInput, ref acc4);
-
-            return Bits.RotateLeft(acc1, 1)
-                   + Bits.RotateLeft(acc2, 7)
-                   + Bits.RotateLeft(acc3, 12)
-                   + Bits.RotateLeft(acc4, 18);
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe void processLane32(ref byte* pInput, ref uint accn)
-        {
-            uint lane = *(uint*)pInput;
-            accn = round32(accn, lane);
-            pInput += 4;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe uint processRemaining32(
-            byte* pInput,
-            uint acc,
-            int remainingLen)
-        {
-            for (uint lane; remainingLen >= 4; remainingLen -= 4, pInput += 4)
-            {
-                lane = *(uint*)pInput;
-                acc += lane * k_Prime32v3;
-                acc = Bits.RotateLeft(acc, 17) * k_Prime32v4;
-            }
-
-            for (byte lane; remainingLen >= 1; remainingLen--, pInput++)
-            {
-                lane = *pInput;
-                acc += lane * k_Prime32v5;
-                acc = Bits.RotateLeft(acc, 11) * k_Prime32v1;
-            }
-
-            return acc;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static uint round32(uint accn, uint lane)
-        {
-            accn += lane * k_Prime32v2;
-            accn = Bits.RotateLeft(accn, 13);
-            accn *= k_Prime32v1;
-            return accn;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static uint avalanche32(uint acc)
-        {
-            acc ^= acc >> 15;
-            acc *= k_Prime32v2;
-            acc ^= acc >> 13;
-            acc *= k_Prime32v3;
-            acc ^= acc >> 16;
-            return acc;
-        }
-
-        /// <summary>
-        /// Bit operations.
-        /// </summary>
-        private static class Bits
-        {
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            internal static ulong RotateLeft(ulong value, int bits)
-            {
-                return (value << bits) | (value >> (64 - bits));
-            }
-
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            internal static uint RotateLeft(uint value, int bits)
-            {
-                return (value << bits) | (value >> (32 - bits));
-            }
-        }
-    }
-}

Runtime/Logging/NetworkLog.cs

@@ -14,8 +14,23 @@ namespace Unity.Netcode
         public static LogLevel CurrentLogLevel => NetworkManager.Singleton == null ? LogLevel.Normal : NetworkManager.Singleton.LogLevel;
 
         // internal logging
+
+        /// <summary>
+        /// Locally logs a info log with Netcode prefixing.
+        /// </summary>
+        /// <param name="message">The message to log</param>
         public static void LogInfo(string message) => Debug.Log($"[Netcode] {message}");
+
+        /// <summary>
+        /// Locally logs a warning log with Netcode prefixing.
+        /// </summary>
+        /// <param name="message">The message to log</param>
         public static void LogWarning(string message) => Debug.LogWarning($"[Netcode] {message}");
+
+        /// <summary>
+        /// Locally logs a error log with Netcode prefixing.
+        /// </summary>
+        /// <param name="message">The message to log</param>
         public static void LogError(string message) => Debug.LogError($"[Netcode] {message}");
 
         /// <summary>

Runtime/Messaging/CustomMessageManager.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Unity.Collections;
 
 namespace Unity.Netcode
 {
@@ -68,9 +69,23 @@ namespace Unity.Netcode
 
             if (clientIds == null)
             {
-                throw new ArgumentNullException("You must pass in a valid clientId List");
+                throw new ArgumentNullException(nameof(clientIds), "You must pass in a valid clientId List");
             }
 
+            if (m_NetworkManager.IsHost)
+            {
+                for (var i = 0; i < clientIds.Count; ++i)
+                {
+                    if (clientIds[i] == m_NetworkManager.LocalClientId)
+                    {
+                        InvokeUnnamedMessage(
+                            m_NetworkManager.LocalClientId,
+                            new FastBufferReader(messageBuffer, Allocator.None),
+                            0
+                        );
+                    }
+                }
+            }
             var message = new UnnamedMessage
             {
                 SendData = messageBuffer
@@ -92,6 +107,18 @@ namespace Unity.Netcode
         /// <param name="networkDelivery">The delivery type (QoS) to send data with</param>
         public void SendUnnamedMessage(ulong clientId, FastBufferWriter messageBuffer, NetworkDelivery networkDelivery = NetworkDelivery.ReliableSequenced)
         {
+            if (m_NetworkManager.IsHost)
+            {
+                if (clientId == m_NetworkManager.LocalClientId)
+                {
+                    InvokeUnnamedMessage(
+                        m_NetworkManager.LocalClientId,
+                        new FastBufferReader(messageBuffer, Allocator.None),
+                        0
+                    );
+                    return;
+                }
+            }
             var message = new UnnamedMessage
             {
                 SendData = messageBuffer
@@ -193,6 +220,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Sends a named message to all clients
         /// </summary>
+        /// <param name="messageName">The message name to send</param>
         /// <param name="messageStream">The message stream containing the data</param>
         /// <param name="networkDelivery">The delivery type (QoS) to send data with</param>
         public void SendNamedMessageToAll(string messageName, FastBufferWriter messageStream, NetworkDelivery networkDelivery = NetworkDelivery.ReliableSequenced)
@@ -219,6 +247,20 @@ namespace Unity.Netcode
                     hash = XXHash.Hash64(messageName);
                     break;
             }
+            if (m_NetworkManager.IsHost)
+            {
+                if (clientId == m_NetworkManager.LocalClientId)
+                {
+                    InvokeNamedMessage(
+                        hash,
+                        m_NetworkManager.LocalClientId,
+                        new FastBufferReader(messageStream, Allocator.None),
+                        0
+                    );
+
+                    return;
+                }
+            }
 
             var message = new NamedMessage
             {
@@ -250,7 +292,7 @@ namespace Unity.Netcode
 
             if (clientIds == null)
             {
-                throw new ArgumentNullException("You must pass in a valid clientId List");
+                throw new ArgumentNullException(nameof(clientIds), "You must pass in a valid clientId List");
             }
 
             ulong hash = 0;
@@ -263,6 +305,21 @@ namespace Unity.Netcode
                     hash = XXHash.Hash64(messageName);
                     break;
             }
+            if (m_NetworkManager.IsHost)
+            {
+                for (var i = 0; i < clientIds.Count; ++i)
+                {
+                    if (clientIds[i] == m_NetworkManager.LocalClientId)
+                    {
+                        InvokeNamedMessage(
+                            hash,
+                            m_NetworkManager.LocalClientId,
+                            new FastBufferReader(messageStream, Allocator.None),
+                            0
+                        );
+                    }
+                }
+            }
             var message = new NamedMessage
             {
                 Hash = hash,

Runtime/Messaging/DisconnectReasonMessage.cs

@@ -0,0 +1,50 @@
+namespace Unity.Netcode
+{
+    internal struct DisconnectReasonMessage : INetworkMessage
+    {
+        public string Reason;
+
+        public int Version => 0;
+
+        public void Serialize(FastBufferWriter writer, int targetVersion)
+        {
+            string reasonSent = Reason;
+            if (reasonSent == null)
+            {
+                reasonSent = string.Empty;
+            }
+
+            // Since we don't send a ConnectionApprovedMessage, the version for this message is encded with the message
+            // itself. However, note that we HAVE received a ConnectionRequestMessage, so we DO have a valid targetVersion
+            // on this side of things - we just have to make sure the receiving side knows what version we sent it,
+            // since whoever has the higher version number is responsible for versioning and they may be the one
+            // with the higher version number.
+            BytePacker.WriteValueBitPacked(writer, Version);
+
+            if (writer.TryBeginWrite(FastBufferWriter.GetWriteSize(reasonSent)))
+            {
+                writer.WriteValue(reasonSent);
+            }
+            else
+            {
+                writer.WriteValueSafe(string.Empty);
+                NetworkLog.LogWarning(
+                    "Disconnect reason didn't fit. Disconnected without sending a reason. Consider shortening the reason string.");
+            }
+        }
+
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
+        {
+            // Since we don't get a ConnectionApprovedMessage, the version for this message is encded with the message
+            // itself. This will override what we got from MessagingSystem... which will always be 0 here.
+            ByteUnpacker.ReadValueBitPacked(reader, out receivedMessageVersion);
+            reader.ReadValueSafe(out Reason);
+            return true;
+        }
+
+        public void Handle(ref NetworkContext context)
+        {
+            ((NetworkManager)context.SystemOwner).DisconnectReason = Reason;
+        }
+    };
+}

Runtime/Messaging/DisconnectReasonMessage.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: d7742516058394f96999464f3ea32c71
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Runtime/Messaging/INetworkMessage.cs

@@ -40,8 +40,9 @@ namespace Unity.Netcode
     /// </summary>
     internal interface INetworkMessage
     {
-        void Serialize(FastBufferWriter writer);
+        void Serialize(FastBufferWriter writer, int targetVersion);
-        bool Deserialize(FastBufferReader reader, ref NetworkContext context);
+        bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion);
         void Handle(ref NetworkContext context);
+        int Version { get; }
     }
 }

Runtime/Messaging/Messages/ChangeOwnershipMessage.cs

@@ -2,22 +2,26 @@ namespace Unity.Netcode
 {
     internal struct ChangeOwnershipMessage : INetworkMessage, INetworkSerializeByMemcpy
     {
+        public int Version => 0;
+
         public ulong NetworkObjectId;
         public ulong OwnerClientId;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
-            writer.WriteValueSafe(this);
+            BytePacker.WriteValueBitPacked(writer, NetworkObjectId);
+            BytePacker.WriteValueBitPacked(writer, OwnerClientId);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsClient)
             {
                 return false;
             }
-            reader.ReadValueSafe(out this);
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
+            ByteUnpacker.ReadValueBitPacked(reader, out OwnerClientId);
             if (!networkManager.SpawnManager.SpawnedObjects.ContainsKey(NetworkObjectId))
             {
                 networkManager.DeferredMessageManager.DeferMessage(IDeferredMessageManager.TriggerType.OnSpawn, NetworkObjectId, reader, ref context);

Runtime/Messaging/Messages/ConnectionApprovedMessage.cs

@@ -1,10 +1,12 @@
-using System;
 using System.Collections.Generic;
+using Unity.Collections;
 
 namespace Unity.Netcode
 {
     internal struct ConnectionApprovedMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public ulong OwnerClientId;
         public int NetworkTick;
 
@@ -13,14 +15,26 @@ namespace Unity.Netcode
 
         private FastBufferReader m_ReceivedSceneObjectData;
 
-        public void Serialize(FastBufferWriter writer)
+        public NativeArray<MessageVersionData> MessageVersions;
+
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
-            if (!writer.TryBeginWrite(sizeof(ulong) + sizeof(int) + sizeof(int)))
+            // ============================================================
+            // BEGIN FORBIDDEN SEGMENT
+            // DO NOT CHANGE THIS HEADER. Everything added to this message
+            // must go AFTER the message version header.
+            // ============================================================
+            BytePacker.WriteValueBitPacked(writer, MessageVersions.Length);
+            foreach (var messageVersion in MessageVersions)
             {
-                throw new OverflowException($"Not enough space in the write buffer to serialize {nameof(ConnectionApprovedMessage)}");
+                messageVersion.Serialize(writer);
             }
-            writer.WriteValue(OwnerClientId);
+            // ============================================================
-            writer.WriteValue(NetworkTick);
+            // END FORBIDDEN SEGMENT
+            // ============================================================
+
+            BytePacker.WriteValueBitPacked(writer, OwnerClientId);
+            BytePacker.WriteValueBitPacked(writer, NetworkTick);
 
             uint sceneObjectCount = 0;
             if (SpawnedObjectsList != null)
@@ -39,17 +53,19 @@ namespace Unity.Netcode
                         ++sceneObjectCount;
                     }
                 }
+
                 writer.Seek(pos);
-                writer.WriteValue(sceneObjectCount);
+                // Can't pack this value because its space is reserved, so it needs to always use all the reserved space.
+                writer.WriteValueSafe(sceneObjectCount);
                 writer.Seek(writer.Length);
             }
             else
             {
-                writer.WriteValue(sceneObjectCount);
+                writer.WriteValueSafe(sceneObjectCount);
             }
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsClient)
@@ -57,13 +73,36 @@ namespace Unity.Netcode
                 return false;
             }
 
-            if (!reader.TryBeginRead(sizeof(ulong) + sizeof(int) + sizeof(int)))
+            // ============================================================
+            // BEGIN FORBIDDEN SEGMENT
+            // DO NOT CHANGE THIS HEADER. Everything added to this message
+            // must go AFTER the message version header.
+            // ============================================================
+            ByteUnpacker.ReadValueBitPacked(reader, out int length);
+            var messageHashesInOrder = new NativeArray<uint>(length, Allocator.Temp);
+            for (var i = 0; i < length; ++i)
             {
-                throw new OverflowException($"Not enough space in the buffer to read {nameof(ConnectionApprovedMessage)}");
+                var messageVersion = new MessageVersionData();
-            }
+                messageVersion.Deserialize(reader);
+                networkManager.MessagingSystem.SetVersion(context.SenderId, messageVersion.Hash, messageVersion.Version);
+                messageHashesInOrder[i] = messageVersion.Hash;
 
-            reader.ReadValue(out OwnerClientId);
+                // Update the received version since this message will always be passed version 0, due to the map not
-            reader.ReadValue(out NetworkTick);
+                // being initialized until just now.
+                var messageType = networkManager.MessagingSystem.GetMessageForHash(messageVersion.Hash);
+                if (messageType == typeof(ConnectionApprovedMessage))
+                {
+                    receivedMessageVersion = messageVersion.Version;
+                }
+            }
+            networkManager.MessagingSystem.SetServerMessageOrder(messageHashesInOrder);
+            messageHashesInOrder.Dispose();
+            // ============================================================
+            // END FORBIDDEN SEGMENT
+            // ============================================================
+
+            ByteUnpacker.ReadValueBitPacked(reader, out OwnerClientId);
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkTick);
             m_ReceivedSceneObjectData = reader;
             return true;
         }
@@ -79,12 +118,13 @@ namespace Unity.Netcode
             networkManager.NetworkTickSystem.Reset(networkManager.NetworkTimeSystem.LocalTime, networkManager.NetworkTimeSystem.ServerTime);
 
             networkManager.LocalClient = new NetworkClient() { ClientId = networkManager.LocalClientId };
+            networkManager.IsApproved = true;
 
             // Only if scene management is disabled do we handle NetworkObject synchronization at this point
             if (!networkManager.NetworkConfig.EnableSceneManagement)
             {
                 networkManager.SpawnManager.DestroySceneObjects();
-                m_ReceivedSceneObjectData.ReadValue(out uint sceneObjectCount);
+                m_ReceivedSceneObjectData.ReadValueSafe(out uint sceneObjectCount);
 
                 // Deserializing NetworkVariable data is deferred from Receive() to Handle to avoid needing
                 // to create a list to hold the data. This is a breach of convention for performance reasons.

Runtime/Messaging/Messages/ConnectionRequestMessage.cs

@@ -1,15 +1,35 @@
+using Unity.Collections;
+
 namespace Unity.Netcode
 {
     internal struct ConnectionRequestMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public ulong ConfigHash;
 
         public byte[] ConnectionData;
 
         public bool ShouldSendConnectionData;
 
-        public void Serialize(FastBufferWriter writer)
+        public NativeArray<MessageVersionData> MessageVersions;
+
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
+            // ============================================================
+            // BEGIN FORBIDDEN SEGMENT
+            // DO NOT CHANGE THIS HEADER. Everything added to this message
+            // must go AFTER the message version header.
+            // ============================================================
+            BytePacker.WriteValueBitPacked(writer, MessageVersions.Length);
+            foreach (var messageVersion in MessageVersions)
+            {
+                messageVersion.Serialize(writer);
+            }
+            // ============================================================
+            // END FORBIDDEN SEGMENT
+            // ============================================================
+
             if (ShouldSendConnectionData)
             {
                 writer.WriteValueSafe(ConfigHash);
@@ -21,7 +41,7 @@ namespace Unity.Netcode
             }
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsServer)
@@ -29,6 +49,30 @@ namespace Unity.Netcode
                 return false;
             }
 
+            // ============================================================
+            // BEGIN FORBIDDEN SEGMENT
+            // DO NOT CHANGE THIS HEADER. Everything added to this message
+            // must go AFTER the message version header.
+            // ============================================================
+            ByteUnpacker.ReadValueBitPacked(reader, out int length);
+            for (var i = 0; i < length; ++i)
+            {
+                var messageVersion = new MessageVersionData();
+                messageVersion.Deserialize(reader);
+                networkManager.MessagingSystem.SetVersion(context.SenderId, messageVersion.Hash, messageVersion.Version);
+
+                // Update the received version since this message will always be passed version 0, due to the map not
+                // being initialized until just now.
+                var messageType = networkManager.MessagingSystem.GetMessageForHash(messageVersion.Hash);
+                if (messageType == typeof(ConnectionRequestMessage))
+                {
+                    receivedMessageVersion = messageVersion.Version;
+                }
+            }
+            // ============================================================
+            // END FORBIDDEN SEGMENT
+            // ============================================================
+
             if (networkManager.NetworkConfig.ConnectionApproval)
             {
                 if (!reader.TryBeginRead(FastBufferWriter.GetWriteSize(ConfigHash) + FastBufferWriter.GetWriteSize<int>()))

Runtime/Messaging/Messages/CreateObjectMessage.cs

@@ -2,15 +2,17 @@ namespace Unity.Netcode
 {
     internal struct CreateObjectMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public NetworkObject.SceneObject ObjectInfo;
         private FastBufferReader m_ReceivedNetworkVariableData;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
             ObjectInfo.Serialize(writer);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsClient)
@@ -21,7 +23,7 @@ namespace Unity.Netcode
             ObjectInfo.Deserialize(reader);
             if (!networkManager.NetworkConfig.ForceSamePrefabs && !networkManager.SpawnManager.HasPrefab(ObjectInfo))
             {
-                networkManager.DeferredMessageManager.DeferMessage(IDeferredMessageManager.TriggerType.OnAddPrefab, ObjectInfo.Header.Hash, reader, ref context);
+                networkManager.DeferredMessageManager.DeferMessage(IDeferredMessageManager.TriggerType.OnAddPrefab, ObjectInfo.Hash, reader, ref context);
                 return false;
             }
             m_ReceivedNetworkVariableData = reader;

Runtime/Messaging/Messages/DestroyObjectMessage.cs

@@ -2,15 +2,18 @@ namespace Unity.Netcode
 {
     internal struct DestroyObjectMessage : INetworkMessage, INetworkSerializeByMemcpy
     {
+        public int Version => 0;
+
         public ulong NetworkObjectId;
         public bool DestroyGameObject;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
-            writer.WriteValueSafe(this);
+            BytePacker.WriteValueBitPacked(writer, NetworkObjectId);
+            writer.WriteValueSafe(DestroyGameObject);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsClient)
@@ -18,7 +21,8 @@ namespace Unity.Netcode
                 return false;
             }
 
-            reader.ReadValueSafe(out this);
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
+            reader.ReadValueSafe(out DestroyGameObject);
 
             if (!networkManager.SpawnManager.SpawnedObjects.TryGetValue(NetworkObjectId, out var networkObject))
             {

Runtime/Messaging/Messages/MessageMetadata.cs

@@ -0,0 +1,23 @@
+namespace Unity.Netcode
+{
+    /// <summary>
+    /// Conveys a version number on a remote node for the given message (identified by its hash)
+    /// </summary>
+    internal struct MessageVersionData
+    {
+        public uint Hash;
+        public int Version;
+
+        public void Serialize(FastBufferWriter writer)
+        {
+            writer.WriteValueSafe(Hash);
+            BytePacker.WriteValueBitPacked(writer, Version);
+        }
+
+        public void Deserialize(FastBufferReader reader)
+        {
+            reader.ReadValueSafe(out Hash);
+            ByteUnpacker.ReadValueBitPacked(reader, out Version);
+        }
+    }
+}

Runtime/Messaging/Messages/MessageMetadata.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 754d727b316b4263a2fa0d4c54fdad52
+timeCreated: 1666895514

Runtime/Messaging/Messages/NamedMessage.cs

@@ -2,18 +2,20 @@ namespace Unity.Netcode
 {
     internal struct NamedMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public ulong Hash;
         public FastBufferWriter SendData;
 
         private FastBufferReader m_ReceiveData;
 
-        public unsafe void Serialize(FastBufferWriter writer)
+        public unsafe void Serialize(FastBufferWriter writer, int targetVersion)
         {
             writer.WriteValueSafe(Hash);
             writer.WriteBytesSafe(SendData.GetUnsafePtr(), SendData.Length);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             reader.ReadValueSafe(out Hash);
             m_ReceiveData = reader;

Runtime/Messaging/Messages/NetworkVariableDeltaMessage.cs

@@ -12,6 +12,8 @@ namespace Unity.Netcode
     /// </summary>
     internal struct NetworkVariableDeltaMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public ulong NetworkObjectId;
         public ushort NetworkBehaviourIndex;
 
@@ -21,15 +23,15 @@ namespace Unity.Netcode
 
         private FastBufferReader m_ReceivedNetworkVariableData;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
             if (!writer.TryBeginWrite(FastBufferWriter.GetWriteSize(NetworkObjectId) + FastBufferWriter.GetWriteSize(NetworkBehaviourIndex)))
             {
                 throw new OverflowException($"Not enough space in the buffer to write {nameof(NetworkVariableDeltaMessage)}");
             }
 
-            writer.WriteValue(NetworkObjectId);
+            BytePacker.WriteValueBitPacked(writer, NetworkObjectId);
-            writer.WriteValue(NetworkBehaviourIndex);
+            BytePacker.WriteValueBitPacked(writer, NetworkBehaviourIndex);
 
             for (int i = 0; i < NetworkBehaviour.NetworkVariableFields.Count; i++)
             {
@@ -38,7 +40,7 @@ namespace Unity.Netcode
                     // This var does not belong to the currently iterating delivery group.
                     if (NetworkBehaviour.NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
                     {
-                        writer.WriteValueSafe((ushort)0);
+                        BytePacker.WriteValueBitPacked(writer, (ushort)0);
                     }
                     else
                     {
@@ -66,7 +68,7 @@ namespace Unity.Netcode
                 {
                     if (!shouldWrite)
                     {
-                        BytePacker.WriteValueBitPacked(writer, 0);
+                        BytePacker.WriteValueBitPacked(writer, (ushort)0);
                     }
                 }
                 else
@@ -110,15 +112,10 @@ namespace Unity.Netcode
             }
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
-            if (!reader.TryBeginRead(FastBufferWriter.GetWriteSize(NetworkObjectId) + FastBufferWriter.GetWriteSize(NetworkBehaviourIndex)))
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
-            {
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkBehaviourIndex);
-                throw new OverflowException($"Not enough data in the buffer to read {nameof(NetworkVariableDeltaMessage)}");
-            }
-
-            reader.ReadValue(out NetworkObjectId);
-            reader.ReadValue(out NetworkBehaviourIndex);
 
             m_ReceivedNetworkVariableData = reader;
 

Runtime/Messaging/Messages/ParentSyncMessage.cs

@@ -1,32 +1,65 @@
+using UnityEngine;
+
 namespace Unity.Netcode
 {
     internal struct ParentSyncMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public ulong NetworkObjectId;
 
-        public bool IsReparented;
+        private byte m_BitField;
+
+        public bool WorldPositionStays
+        {
+            get => ByteUtility.GetBit(m_BitField, 0);
+            set => ByteUtility.SetBit(ref m_BitField, 0, value);
+        }
 
         //If(Metadata.IsReparented)
-        public bool IsLatestParentSet;
+        public bool IsLatestParentSet
+        {
+            get => ByteUtility.GetBit(m_BitField, 1);
+            set => ByteUtility.SetBit(ref m_BitField, 1, value);
+        }
 
         //If(IsLatestParentSet)
         public ulong? LatestParent;
 
-        public void Serialize(FastBufferWriter writer)
+        // Is set when the parent should be removed (similar to IsReparented functionality but only for removing the parent)
+        public bool RemoveParent
         {
-            writer.WriteValueSafe(NetworkObjectId);
+            get => ByteUtility.GetBit(m_BitField, 2);
-            writer.WriteValueSafe(IsReparented);
+            set => ByteUtility.SetBit(ref m_BitField, 2, value);
-            if (IsReparented)
+        }
+
+        // These additional properties are used to synchronize clients with the current position,
+        // rotation, and scale after parenting/de-parenting (world/local space relative). This
+        // allows users to control the final child's transform values without having to have a
+        // NetworkTransform component on the child. (i.e. picking something up)
+        public Vector3 Position;
+        public Quaternion Rotation;
+        public Vector3 Scale;
+
+        public void Serialize(FastBufferWriter writer, int targetVersion)
+        {
+            BytePacker.WriteValueBitPacked(writer, NetworkObjectId);
+            writer.WriteValueSafe(m_BitField);
+            if (!RemoveParent)
             {
-                writer.WriteValueSafe(IsLatestParentSet);
                 if (IsLatestParentSet)
                 {
-                    writer.WriteValueSafe((ulong)LatestParent);
+                    BytePacker.WriteValueBitPacked(writer, LatestParent.Value);
-                }
                 }
             }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            // Whether parenting or removing a parent, we always update the position, rotation, and scale
+            writer.WriteValueSafe(Position);
+            writer.WriteValueSafe(Rotation);
+            writer.WriteValueSafe(Scale);
+        }
+
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsClient)
@@ -34,24 +67,27 @@ namespace Unity.Netcode
                 return false;
             }
 
-            reader.ReadValueSafe(out NetworkObjectId);
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
-            reader.ReadValueSafe(out IsReparented);
+            reader.ReadValueSafe(out m_BitField);
-            if (IsReparented)
+            if (!RemoveParent)
             {
-                reader.ReadValueSafe(out IsLatestParentSet);
                 if (IsLatestParentSet)
                 {
-                    reader.ReadValueSafe(out ulong latestParent);
+                    ByteUnpacker.ReadValueBitPacked(reader, out ulong latestParent);
                     LatestParent = latestParent;
                 }
             }
 
+            // Whether parenting or removing a parent, we always update the position, rotation, and scale
+            reader.ReadValueSafe(out Position);
+            reader.ReadValueSafe(out Rotation);
+            reader.ReadValueSafe(out Scale);
+
             if (!networkManager.SpawnManager.SpawnedObjects.ContainsKey(NetworkObjectId))
             {
                 networkManager.DeferredMessageManager.DeferMessage(IDeferredMessageManager.TriggerType.OnSpawn, NetworkObjectId, reader, ref context);
                 return false;
             }
-
             return true;
         }
 
@@ -59,8 +95,22 @@ namespace Unity.Netcode
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             var networkObject = networkManager.SpawnManager.SpawnedObjects[NetworkObjectId];
-            networkObject.SetNetworkParenting(IsReparented, LatestParent);
+            networkObject.SetNetworkParenting(LatestParent, WorldPositionStays);
-            networkObject.ApplyNetworkParenting();
+            networkObject.ApplyNetworkParenting(RemoveParent);
+
+            // We set all of the transform values after parenting as they are
+            // the values of the server-side post-parenting transform values
+            if (!WorldPositionStays)
+            {
+                networkObject.transform.localPosition = Position;
+                networkObject.transform.localRotation = Rotation;
+            }
+            else
+            {
+                networkObject.transform.position = Position;
+                networkObject.transform.rotation = Rotation;
+            }
+            networkObject.transform.localScale = Scale;
         }
     }
 }

Runtime/Messaging/Messages/RpcMessages.cs

@@ -8,24 +8,17 @@ namespace Unity.Netcode
     {
         public static unsafe void Serialize(ref FastBufferWriter writer, ref RpcMetadata metadata, ref FastBufferWriter payload)
         {
-            if (!writer.TryBeginWrite(FastBufferWriter.GetWriteSize<RpcMetadata>() + payload.Length))
+            BytePacker.WriteValueBitPacked(writer, metadata.NetworkObjectId);
-            {
+            BytePacker.WriteValueBitPacked(writer, metadata.NetworkBehaviourId);
-                throw new OverflowException("Not enough space in the buffer to store RPC data.");
+            BytePacker.WriteValueBitPacked(writer, metadata.NetworkRpcMethodId);
-            }
+            writer.WriteBytesSafe(payload.GetUnsafePtr(), payload.Length);
-
-            writer.WriteValue(metadata);
-            writer.WriteBytes(payload.GetUnsafePtr(), payload.Length);
         }
 
         public static unsafe bool Deserialize(ref FastBufferReader reader, ref NetworkContext context, ref RpcMetadata metadata, ref FastBufferReader payload)
         {
-            int metadataSize = FastBufferWriter.GetWriteSize<RpcMetadata>();
+            ByteUnpacker.ReadValueBitPacked(reader, out metadata.NetworkObjectId);
-            if (!reader.TryBeginRead(metadataSize))
+            ByteUnpacker.ReadValueBitPacked(reader, out metadata.NetworkBehaviourId);
-            {
+            ByteUnpacker.ReadValueBitPacked(reader, out metadata.NetworkRpcMethodId);
-                throw new InvalidOperationException("Not enough data in the buffer to read RPC meta.");
-            }
-
-            reader.ReadValue(out metadata);
 
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.SpawnManager.SpawnedObjects.ContainsKey(metadata.NetworkObjectId))
@@ -46,7 +39,7 @@ namespace Unity.Netcode
                 return false;
             }
 
-            payload = new FastBufferReader(reader.GetUnsafePtr() + metadataSize, Allocator.None, reader.Length - metadataSize);
+            payload = new FastBufferReader(reader.GetUnsafePtrAtCurrentPosition(), Allocator.None, reader.Length - reader.Position);
 
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
             if (NetworkManager.__rpc_name_table.TryGetValue(metadata.NetworkRpcMethodId, out var rpcMethodName))
@@ -92,17 +85,19 @@ namespace Unity.Netcode
 
     internal struct ServerRpcMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public RpcMetadata Metadata;
 
         public FastBufferWriter WriteBuffer;
         public FastBufferReader ReadBuffer;
 
-        public unsafe void Serialize(FastBufferWriter writer)
+        public unsafe void Serialize(FastBufferWriter writer, int targetVersion)
         {
             RpcMessageHelpers.Serialize(ref writer, ref Metadata, ref WriteBuffer);
         }
 
-        public unsafe bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public unsafe bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             return RpcMessageHelpers.Deserialize(ref reader, ref context, ref Metadata, ref ReadBuffer);
         }
@@ -125,17 +120,19 @@ namespace Unity.Netcode
 
     internal struct ClientRpcMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public RpcMetadata Metadata;
 
         public FastBufferWriter WriteBuffer;
         public FastBufferReader ReadBuffer;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
             RpcMessageHelpers.Serialize(ref writer, ref Metadata, ref WriteBuffer);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             return RpcMessageHelpers.Deserialize(ref reader, ref context, ref Metadata, ref ReadBuffer);
         }

Runtime/Messaging/Messages/SceneEventMessage.cs

@@ -4,16 +4,18 @@ namespace Unity.Netcode
     // like most of the other messages when we have some more time and can come back and refactor this.
     internal struct SceneEventMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public SceneEventData EventData;
 
         private FastBufferReader m_ReceivedData;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
             EventData.Serialize(writer);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             m_ReceivedData = reader;
             return true;

Runtime/Messaging/Messages/ServerLogMessage.cs

@@ -2,6 +2,8 @@ namespace Unity.Netcode
 {
     internal struct ServerLogMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public NetworkLog.LogType LogType;
         // It'd be lovely to be able to replace this with FixedString or NativeArray...
         // But it's not really practical. On the sending side, the user is likely to want
@@ -11,13 +13,13 @@ namespace Unity.Netcode
         public string Message;
 
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
             writer.WriteValueSafe(LogType);
             BytePacker.WriteValuePacked(writer, Message);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (networkManager.IsServer && networkManager.NetworkConfig.EnableNetworkLogs)

Runtime/Messaging/Messages/TimeSyncMessage.cs

@@ -2,21 +2,23 @@ namespace Unity.Netcode
 {
     internal struct TimeSyncMessage : INetworkMessage, INetworkSerializeByMemcpy
     {
+        public int Version => 0;
+
         public int Tick;
 
-        public void Serialize(FastBufferWriter writer)
+        public void Serialize(FastBufferWriter writer, int targetVersion)
         {
-            writer.WriteValueSafe(this);
+            BytePacker.WriteValueBitPacked(writer, Tick);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             var networkManager = (NetworkManager)context.SystemOwner;
             if (!networkManager.IsClient)
             {
                 return false;
             }
-            reader.ReadValueSafe(out this);
+            ByteUnpacker.ReadValueBitPacked(reader, out Tick);
             return true;
         }
 

Runtime/Messaging/Messages/UnnamedMessage.cs

@@ -2,15 +2,17 @@ namespace Unity.Netcode
 {
     internal struct UnnamedMessage : INetworkMessage
     {
+        public int Version => 0;
+
         public FastBufferWriter SendData;
         private FastBufferReader m_ReceivedData;
 
-        public unsafe void Serialize(FastBufferWriter writer)
+        public unsafe void Serialize(FastBufferWriter writer, int targetVersion)
         {
             writer.WriteBytesSafe(SendData.GetUnsafePtr(), SendData.Length);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
         {
             m_ReceivedData = reader;
             return true;

Runtime/Messaging/MessagingSystem.cs

@@ -8,6 +8,11 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
+    internal class HandlerNotRegisteredException : SystemException
+    {
+        public HandlerNotRegisteredException() { }
+        public HandlerNotRegisteredException(string issue) : base(issue) { }
+    }
 
     internal class InvalidMessageStructureException : SystemException
     {
@@ -41,15 +46,22 @@ namespace Unity.Netcode
         }
 
         internal delegate void MessageHandler(FastBufferReader reader, ref NetworkContext context, MessagingSystem system);
+        internal delegate int VersionGetter();
 
         private NativeList<ReceiveQueueItem> m_IncomingMessageQueue = new NativeList<ReceiveQueueItem>(16, Allocator.Persistent);
 
-        private MessageHandler[] m_MessageHandlers = new MessageHandler[255];
+        // These array will grow as we need more message handlers. 4 is just a starting size.
-        private Type[] m_ReverseTypeMap = new Type[255];
+        private MessageHandler[] m_MessageHandlers = new MessageHandler[4];
+        private Type[] m_ReverseTypeMap = new Type[4];
 
         private Dictionary<Type, uint> m_MessageTypes = new Dictionary<Type, uint>();
         private Dictionary<ulong, NativeList<SendQueueItem>> m_SendQueues = new Dictionary<ulong, NativeList<SendQueueItem>>();
 
+        // This is m_PerClientMessageVersion[clientId][messageType] = version
+        private Dictionary<ulong, Dictionary<Type, int>> m_PerClientMessageVersions = new Dictionary<ulong, Dictionary<Type, int>>();
+        private Dictionary<uint, Type> m_MessagesByHash = new Dictionary<uint, Type>();
+        private Dictionary<Type, int> m_LocalVersions = new Dictionary<Type, int>();
+
         private List<INetworkHooks> m_Hooks = new List<INetworkHooks>();
 
         private uint m_HighMessageType;
@@ -59,6 +71,7 @@ namespace Unity.Netcode
 
         internal Type[] MessageTypes => m_ReverseTypeMap;
         internal MessageHandler[] MessageHandlers => m_MessageHandlers;
+
         internal uint MessageHandlerCount => m_HighMessageType;
 
         internal uint GetMessageType(Type t)
@@ -67,12 +80,40 @@ namespace Unity.Netcode
         }
 
         public const int NON_FRAGMENTED_MESSAGE_MAX_SIZE = 1300;
-        public const int FRAGMENTED_MESSAGE_MAX_SIZE = BytePacker.BitPackedIntMax;
+        public const int FRAGMENTED_MESSAGE_MAX_SIZE = int.MaxValue;
 
         internal struct MessageWithHandler
         {
             public Type MessageType;
             public MessageHandler Handler;
+            public VersionGetter GetVersion;
+        }
+
+        internal List<MessageWithHandler> PrioritizeMessageOrder(List<MessageWithHandler> allowedTypes)
+        {
+            var prioritizedTypes = new List<MessageWithHandler>();
+
+            // first pass puts the priority message in the first indices
+            // Those are the messages that must be delivered in order to allow re-ordering the others later
+            foreach (var t in allowedTypes)
+            {
+                if (t.MessageType.FullName == typeof(ConnectionRequestMessage).FullName ||
+                    t.MessageType.FullName == typeof(ConnectionApprovedMessage).FullName)
+                {
+                    prioritizedTypes.Add(t);
+                }
+            }
+
+            foreach (var t in allowedTypes)
+            {
+                if (t.MessageType.FullName != typeof(ConnectionRequestMessage).FullName &&
+                    t.MessageType.FullName != typeof(ConnectionApprovedMessage).FullName)
+                {
+                    prioritizedTypes.Add(t);
+                }
+            }
+
+            return prioritizedTypes;
         }
 
         public MessagingSystem(IMessageSender messageSender, object owner, IMessageProvider provider = null)
@@ -89,6 +130,7 @@ namespace Unity.Netcode
                 var allowedTypes = provider.GetMessages();
 
                 allowedTypes.Sort((a, b) => string.CompareOrdinal(a.MessageType.FullName, b.MessageType.FullName));
+                allowedTypes = PrioritizeMessageOrder(allowedTypes);
                 foreach (var type in allowedTypes)
                 {
                     RegisterMessageType(type);
@@ -143,9 +185,23 @@ namespace Unity.Netcode
 
         private void RegisterMessageType(MessageWithHandler messageWithHandler)
         {
+            // if we are out of space, perform amortized linear growth
+            if (m_HighMessageType == m_MessageHandlers.Length)
+            {
+                Array.Resize(ref m_MessageHandlers, 2 * m_MessageHandlers.Length);
+                Array.Resize(ref m_ReverseTypeMap, 2 * m_ReverseTypeMap.Length);
+            }
+
             m_MessageHandlers[m_HighMessageType] = messageWithHandler.Handler;
             m_ReverseTypeMap[m_HighMessageType] = messageWithHandler.MessageType;
+            m_MessagesByHash[XXHash.Hash32(messageWithHandler.MessageType.FullName)] = messageWithHandler.MessageType;
             m_MessageTypes[messageWithHandler.MessageType] = m_HighMessageType++;
+            m_LocalVersions[messageWithHandler.MessageType] = messageWithHandler.GetVersion();
+        }
+
+        public int GetLocalVersion(Type messageType)
+        {
+            return m_LocalVersions[messageType];
         }
 
         internal void HandleIncomingData(ulong clientId, ArraySegment<byte> data, float receiveTime)
@@ -226,6 +282,55 @@ namespace Unity.Netcode
             return true;
         }
 
+        internal Type GetMessageForHash(uint messageHash)
+        {
+            if (!m_MessagesByHash.ContainsKey(messageHash))
+            {
+                return null;
+            }
+            return m_MessagesByHash[messageHash];
+        }
+
+        internal void SetVersion(ulong clientId, uint messageHash, int version)
+        {
+            if (!m_MessagesByHash.ContainsKey(messageHash))
+            {
+                return;
+            }
+            var messageType = m_MessagesByHash[messageHash];
+
+            if (!m_PerClientMessageVersions.ContainsKey(clientId))
+            {
+                m_PerClientMessageVersions[clientId] = new Dictionary<Type, int>();
+            }
+
+            m_PerClientMessageVersions[clientId][messageType] = version;
+        }
+
+        internal void SetServerMessageOrder(NativeArray<uint> messagesInIdOrder)
+        {
+            var oldHandlers = m_MessageHandlers;
+            var oldTypes = m_MessageTypes;
+            m_ReverseTypeMap = new Type[messagesInIdOrder.Length];
+            m_MessageHandlers = new MessageHandler[messagesInIdOrder.Length];
+            m_MessageTypes = new Dictionary<Type, uint>();
+
+            for (var i = 0; i < messagesInIdOrder.Length; ++i)
+            {
+                if (!m_MessagesByHash.ContainsKey(messagesInIdOrder[i]))
+                {
+                    continue;
+                }
+                var messageType = m_MessagesByHash[messagesInIdOrder[i]];
+                var oldId = oldTypes[messageType];
+                var handler = oldHandlers[oldId];
+                var newId = (uint)i;
+                m_MessageTypes[messageType] = newId;
+                m_MessageHandlers[newId] = handler;
+                m_ReverseTypeMap[newId] = messageType;
+            }
+        }
+
         public void HandleMessage(in MessageHeader header, FastBufferReader reader, ulong senderId, float timestamp, int serializedHeaderSize)
         {
             if (header.MessageType >= m_HighMessageType)
@@ -258,6 +363,16 @@ namespace Unity.Netcode
 
             var handler = m_MessageHandlers[header.MessageType];
             using (reader)
+            {
+                // This will also log an exception is if the server knows about a message type the client doesn't know
+                // about. In this case the handler will be null. It is still an issue the user must deal with: If the
+                // two connecting builds know about different messages, the server should not send a message to a client
+                // that doesn't know about it
+                if (handler == null)
+                {
+                    Debug.LogException(new HandlerNotRegisteredException(header.MessageType.ToString()));
+                }
+                else
                 {
                     // No user-land message handler exceptions should escape the receive loop.
                     // If an exception is throw, the message is ignored.
@@ -273,6 +388,7 @@ namespace Unity.Netcode
                         Debug.LogException(e);
                     }
                 }
+            }
             for (var hookIdx = 0; hookIdx < m_Hooks.Count; ++hookIdx)
             {
                 m_Hooks[hookIdx].OnAfterReceiveMessage(senderId, type, reader.Length + FastBufferWriter.GetWriteSize<MessageHeader>());
@@ -314,7 +430,7 @@ namespace Unity.Netcode
             m_SendQueues.Remove(clientId);
         }
 
-        private unsafe void CleanupDisconnectedClient(ulong clientId)
+        private void CleanupDisconnectedClient(ulong clientId)
         {
             var queue = m_SendQueues[clientId];
             for (var i = 0; i < queue.Length; ++i)
@@ -325,10 +441,67 @@ namespace Unity.Netcode
             queue.Dispose();
         }
 
+        internal void CleanupDisconnectedClients()
+        {
+            var removeList = new NativeList<ulong>(Allocator.Temp);
+            foreach (var clientId in m_PerClientMessageVersions.Keys)
+            {
+                if (!m_SendQueues.ContainsKey(clientId))
+                {
+                    removeList.Add(clientId);
+                }
+            }
+
+            foreach (var clientId in removeList)
+            {
+                m_PerClientMessageVersions.Remove(clientId);
+            }
+        }
+
+        public static int CreateMessageAndGetVersion<T>() where T : INetworkMessage, new()
+        {
+            return new T().Version;
+        }
+
+        internal int GetMessageVersion(Type type, ulong clientId, bool forReceive = false)
+        {
+            if (!m_PerClientMessageVersions.TryGetValue(clientId, out var versionMap))
+            {
+                if (forReceive)
+                {
+                    Debug.LogWarning($"Trying to receive {type.Name} from client {clientId} which is not in a connected state.");
+
+                }
+                else
+                {
+                    Debug.LogWarning($"Trying to send {type.Name} to client {clientId} which is not in a connected state.");
+                }
+                return -1;
+            }
+            if (!versionMap.TryGetValue(type, out var messageVersion))
+            {
+                return -1;
+            }
+
+            return messageVersion;
+        }
+
         public static void ReceiveMessage<T>(FastBufferReader reader, ref NetworkContext context, MessagingSystem system) where T : INetworkMessage, new()
         {
             var message = new T();
-            if (message.Deserialize(reader, ref context))
+            var messageVersion = 0;
+            // Special cases because these are the messages that carry the version info - thus the version info isn't
+            // populated yet when we get these. The first part of these messages always has to be the version data
+            // and can't change.
+            if (typeof(T) != typeof(ConnectionRequestMessage) && typeof(T) != typeof(ConnectionApprovedMessage) && typeof(T) != typeof(DisconnectReasonMessage))
+            {
+                messageVersion = system.GetMessageVersion(typeof(T), context.SenderId, true);
+                if (messageVersion < 0)
+                {
+                    return;
+                }
+            }
+            if (message.Deserialize(reader, ref context, messageVersion))
             {
                 for (var hookIdx = 0; hookIdx < system.m_Hooks.Count; ++hookIdx)
                 {
@@ -366,16 +539,47 @@ namespace Unity.Netcode
                 return 0;
             }
 
+            var largestSerializedSize = 0;
+            var sentMessageVersions = new NativeHashSet<int>(clientIds.Count, Allocator.Temp);
+            for (var i = 0; i < clientIds.Count; ++i)
+            {
+                var messageVersion = 0;
+                // Special case because this is the message that carries the version info - thus the version info isn't
+                // populated yet when we get this. The first part of this message always has to be the version data
+                // and can't change.
+                if (typeof(TMessageType) != typeof(ConnectionRequestMessage))
+                {
+                    messageVersion = GetMessageVersion(typeof(TMessageType), clientIds[i]);
+                    if (messageVersion < 0)
+                    {
+                        // Client doesn't know this message exists, don't send it at all.
+                        continue;
+                    }
+                }
+
+                if (sentMessageVersions.Contains(messageVersion))
+                {
+                    continue;
+                }
+
+                sentMessageVersions.Add(messageVersion);
+
                 var maxSize = delivery == NetworkDelivery.ReliableFragmentedSequenced ? FRAGMENTED_MESSAGE_MAX_SIZE : NON_FRAGMENTED_MESSAGE_MAX_SIZE;
 
                 using var tmpSerializer = new FastBufferWriter(NON_FRAGMENTED_MESSAGE_MAX_SIZE - FastBufferWriter.GetWriteSize<MessageHeader>(), Allocator.Temp, maxSize - FastBufferWriter.GetWriteSize<MessageHeader>());
 
-            message.Serialize(tmpSerializer);
+                message.Serialize(tmpSerializer, messageVersion);
 
-            return SendPreSerializedMessage(tmpSerializer, maxSize, ref message, delivery, clientIds);
+                var size = SendPreSerializedMessage(tmpSerializer, maxSize, ref message, delivery, clientIds, messageVersion);
+                largestSerializedSize = size > largestSerializedSize ? size : largestSerializedSize;
             }
 
-        internal unsafe int SendPreSerializedMessage<TMessageType>(in FastBufferWriter tmpSerializer, int maxSize, ref TMessageType message, NetworkDelivery delivery, in IReadOnlyList<ulong> clientIds)
+            sentMessageVersions.Dispose();
+
+            return largestSerializedSize;
+        }
+
+        internal unsafe int SendPreSerializedMessage<TMessageType>(in FastBufferWriter tmpSerializer, int maxSize, ref TMessageType message, NetworkDelivery delivery, in IReadOnlyList<ulong> clientIds, int messageVersionFilter)
             where TMessageType : INetworkMessage
         {
             using var headerSerializer = new FastBufferWriter(FastBufferWriter.GetWriteSize<MessageHeader>(), Allocator.Temp);
@@ -390,6 +594,25 @@ namespace Unity.Netcode
 
             for (var i = 0; i < clientIds.Count; ++i)
             {
+                var messageVersion = 0;
+                // Special case because this is the message that carries the version info - thus the version info isn't
+                // populated yet when we get this. The first part of this message always has to be the version data
+                // and can't change.
+                if (typeof(TMessageType) != typeof(ConnectionRequestMessage))
+                {
+                    messageVersion = GetMessageVersion(typeof(TMessageType), clientIds[i]);
+                    if (messageVersion < 0)
+                    {
+                        // Client doesn't know this message exists, don't send it at all.
+                        continue;
+                    }
+
+                    if (messageVersion != messageVersionFilter)
+                    {
+                        continue;
+                    }
+                }
+
                 var clientId = clientIds[i];
 
                 if (!CanSend(clientId, typeof(TMessageType), delivery))
@@ -440,8 +663,22 @@ namespace Unity.Netcode
         internal unsafe int SendPreSerializedMessage<TMessageType>(in FastBufferWriter tmpSerializer, int maxSize, ref TMessageType message, NetworkDelivery delivery, ulong clientId)
             where TMessageType : INetworkMessage
         {
+            var messageVersion = 0;
+            // Special case because this is the message that carries the version info - thus the version info isn't
+            // populated yet when we get this. The first part of this message always has to be the version data
+            // and can't change.
+            if (typeof(TMessageType) != typeof(ConnectionRequestMessage))
+            {
+                messageVersion = GetMessageVersion(typeof(TMessageType), clientId);
+                if (messageVersion < 0)
+                {
+                    // Client doesn't know this message exists, don't send it at all.
+                    return 0;
+                }
+            }
+
             ulong* clientIds = stackalloc ulong[] { clientId };
-            return SendPreSerializedMessage(tmpSerializer, maxSize, ref message, delivery, new PointerListWrapper<ulong>(clientIds, 1));
+            return SendPreSerializedMessage(tmpSerializer, maxSize, ref message, delivery, new PointerListWrapper<ulong>(clientIds, 1), messageVersion);
         }
 
         private struct PointerListWrapper<T> : IReadOnlyList<T>

Runtime/Messaging/RpcParams.cs

@@ -3,21 +3,52 @@ using Unity.Collections;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Server-Side RPC
+    /// Place holder.  <see cref="ServerRpcParams"/>
+    /// Note: Clients always send to one destination when sending RPCs to the server
+    /// so this structure is a place holder
+    /// </summary>
     public struct ServerRpcSendParams
     {
     }
 
+    /// <summary>
+    /// The receive parameters for server-side remote procedure calls
+    /// </summary>
     public struct ServerRpcReceiveParams
     {
+        /// <summary>
+        /// Server-Side RPC
+        /// The client identifier of the sender
+        /// </summary>
         public ulong SenderClientId;
     }
 
+    /// <summary>
+    /// Server-Side RPC
+    /// Can be used with any sever-side remote procedure call
+    /// Note: typically this is use primarily for the <see cref="ServerRpcReceiveParams"/>
+    /// </summary>
     public struct ServerRpcParams
     {
+        /// <summary>
+        /// The server RPC send parameters (currently a place holder)
+        /// </summary>
         public ServerRpcSendParams Send;
+
+        /// <summary>
+        /// The client RPC receive parameters provides you with the sender's identifier
+        /// </summary>
         public ServerRpcReceiveParams Receive;
     }
 
+    /// <summary>
+    /// Client-Side RPC
+    /// The send parameters, when sending client RPCs, provides you wil the ability to
+    /// target specific clients as a managed or unmanaged list:
+    /// <see cref="TargetClientIds"/> and <see cref="TargetClientIdsNativeArray"/>
+    /// </summary>
     public struct ClientRpcSendParams
     {
         /// <summary>
@@ -34,13 +65,32 @@ namespace Unity.Netcode
         public NativeArray<ulong>? TargetClientIdsNativeArray;
     }
 
+    /// <summary>
+    /// Client-Side RPC
+    /// Place holder.  <see cref="ServerRpcParams"/>
+    /// Note: Server will always be the sender, so this structure is a place holder
+    /// </summary>
     public struct ClientRpcReceiveParams
     {
     }
 
+    /// <summary>
+    /// Client-Side RPC
+    /// Can be used with any client-side remote procedure call
+    /// Note: Typically this is used primarily for sending to a specific list
+    /// of clients as opposed to the default (all).
+    /// <see cref="ClientRpcSendParams"/>
+    /// </summary>
     public struct ClientRpcParams
     {
+        /// <summary>
+        /// The client RPC send parameters provides you with the ability to send to a specific list of clients
+        /// </summary>
         public ClientRpcSendParams Send;
+
+        /// <summary>
+        /// The client RPC receive parameters (currently a place holder)
+        /// </summary>
         public ClientRpcReceiveParams Receive;
     }
 

Runtime/Metrics/NetworkMetrics.cs

@@ -5,17 +5,14 @@ using Unity.Multiplayer.Tools;
 using Unity.Multiplayer.Tools.MetricTypes;
 using Unity.Multiplayer.Tools.NetStats;
 using Unity.Profiling;
-using UnityEngine;
 
 namespace Unity.Netcode
 {
     internal class NetworkMetrics : INetworkMetrics
     {
-        const ulong k_MaxMetricsPerFrame = 1000L;
+        private const ulong k_MaxMetricsPerFrame = 1000L;
-
+        private static Dictionary<uint, string> s_SceneEventTypeNames;
-        static Dictionary<uint, string> s_SceneEventTypeNames;
+        private static ProfilerMarker s_FrameDispatch = new ProfilerMarker($"{nameof(NetworkMetrics)}.DispatchFrame");
-
-        static ProfilerMarker s_FrameDispatch = new ProfilerMarker($"{nameof(NetworkMetrics)}.DispatchFrame");
 
         static NetworkMetrics()
         {

Runtime/Metrics/NetworkObjectProvider.cs

@@ -4,7 +4,7 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
-    class NetworkObjectProvider : INetworkObjectProvider
+    internal class NetworkObjectProvider : INetworkObjectProvider
     {
         private readonly NetworkManager m_NetworkManager;
 

Runtime/NetworkVariable/Collections/NetworkList.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using Unity.Collections;
+using UnityEngine;
 
 namespace Unity.Netcode
 {
@@ -11,7 +12,6 @@ namespace Unity.Netcode
     public class NetworkList<T> : NetworkVariableBase where T : unmanaged, IEquatable<T>
     {
         private NativeList<T> m_List = new NativeList<T>(64, Allocator.Persistent);
-        private NativeList<T> m_ListAtLastReset = new NativeList<T>(64, Allocator.Persistent);
         private NativeList<NetworkListEvent<T>> m_DirtyEvents = new NativeList<NetworkListEvent<T>>(64, Allocator.Persistent);
 
         /// <summary>
@@ -25,18 +25,29 @@ namespace Unity.Netcode
         /// </summary>
         public event OnListChangedDelegate OnListChanged;
 
+        /// <summary>
+        /// Constructor method for <see cref="NetworkList"/>
+        /// </summary>
         public NetworkList() { }
 
+        /// <inheritdoc/>
+        /// <param name="values"></param>
+        /// <param name="readPerm"></param>
+        /// <param name="writePerm"></param>
         public NetworkList(IEnumerable<T> values = default,
             NetworkVariableReadPermission readPerm = DefaultReadPerm,
             NetworkVariableWritePermission writePerm = DefaultWritePerm)
             : base(readPerm, writePerm)
+        {
+            // allow null IEnumerable<T> to mean "no values"
+            if (values != null)
             {
                 foreach (var value in values)
                 {
                     m_List.Add(value);
                 }
             }
+        }
 
         /// <inheritdoc />
         public override void ResetDirty()
@@ -45,7 +56,6 @@ namespace Unity.Netcode
             if (m_DirtyEvents.Length > 0)
             {
                 m_DirtyEvents.Clear();
-                m_ListAtLastReset.CopyFrom(m_List);
             }
         }
 
@@ -56,6 +66,18 @@ namespace Unity.Netcode
             return base.IsDirty() || m_DirtyEvents.Length > 0;
         }
 
+        internal void MarkNetworkObjectDirty()
+        {
+            if (m_NetworkBehaviour == null)
+            {
+                Debug.LogWarning($"NetworkList is written to, but doesn't know its NetworkBehaviour yet. " +
+                                 "Are you modifying a NetworkList before the NetworkObject is spawned?");
+                return;
+            }
+
+            m_NetworkBehaviour.NetworkManager.MarkNetworkObjectDirty(m_NetworkBehaviour.NetworkObject);
+        }
+
         /// <inheritdoc />
         public override void WriteDelta(FastBufferWriter writer)
         {
@@ -115,10 +137,10 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public override void WriteField(FastBufferWriter writer)
         {
-            writer.WriteValueSafe((ushort)m_ListAtLastReset.Length);
+            writer.WriteValueSafe((ushort)m_List.Length);
-            for (int i = 0; i < m_ListAtLastReset.Length; i++)
+            for (int i = 0; i < m_List.Length; i++)
             {
-                NetworkVariableSerialization<T>.Write(writer, ref m_ListAtLastReset.ElementAt(i));
+                NetworkVariableSerialization<T>.Write(writer, ref m_List.ElementAt(i));
             }
         }
 
@@ -129,7 +151,8 @@ namespace Unity.Netcode
             reader.ReadValueSafe(out ushort count);
             for (int i = 0; i < count; i++)
             {
-                NetworkVariableSerialization<T>.Read(reader, out T value);
+                var value = new T();
+                NetworkVariableSerialization<T>.Read(reader, ref value);
                 m_List.Add(value);
             }
         }
@@ -145,7 +168,8 @@ namespace Unity.Netcode
                 {
                     case NetworkListEvent<T>.EventType.Add:
                         {
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
                             m_List.Add(value);
 
                             if (OnListChanged != null)
@@ -166,15 +190,25 @@ namespace Unity.Netcode
                                     Index = m_List.Length - 1,
                                     Value = m_List[m_List.Length - 1]
                                 });
+                                MarkNetworkObjectDirty();
                             }
                         }
                         break;
                     case NetworkListEvent<T>.EventType.Insert:
                         {
                             reader.ReadValueSafe(out int index);
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
+
+                            if (index < m_List.Length)
+                            {
                                 m_List.InsertRangeWithBeginEnd(index, index + 1);
                                 m_List[index] = value;
+                            }
+                            else
+                            {
+                                m_List.Add(value);
+                            }
 
                             if (OnListChanged != null)
                             {
@@ -194,12 +228,14 @@ namespace Unity.Netcode
                                     Index = index,
                                     Value = m_List[index]
                                 });
+                                MarkNetworkObjectDirty();
                             }
                         }
                         break;
                     case NetworkListEvent<T>.EventType.Remove:
                         {
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
                             int index = m_List.IndexOf(value);
                             if (index == -1)
                             {
@@ -226,6 +262,7 @@ namespace Unity.Netcode
                                     Index = index,
                                     Value = value
                                 });
+                                MarkNetworkObjectDirty();
                             }
                         }
                         break;
@@ -253,13 +290,15 @@ namespace Unity.Netcode
                                     Index = index,
                                     Value = value
                                 });
+                                MarkNetworkObjectDirty();
                             }
                         }
                         break;
                     case NetworkListEvent<T>.EventType.Value:
                         {
                             reader.ReadValueSafe(out int index);
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
                             if (index >= m_List.Length)
                             {
                                 throw new Exception("Shouldn't be here, index is higher than list length");
@@ -288,6 +327,7 @@ namespace Unity.Netcode
                                     Value = value,
                                     PreviousValue = previousValue
                                 });
+                                MarkNetworkObjectDirty();
                             }
                         }
                         break;
@@ -310,6 +350,7 @@ namespace Unity.Netcode
                                 {
                                     Type = eventType
                                 });
+                                MarkNetworkObjectDirty();
                             }
                         }
                         break;
@@ -332,6 +373,12 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public void Add(T item)
         {
+            // check write permissions
+            if (!CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
+            {
+                throw new InvalidOperationException("Client is not allowed to write to this NetworkList");
+            }
+
             m_List.Add(item);
 
             var listEvent = new NetworkListEvent<T>()
@@ -347,6 +394,12 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public void Clear()
         {
+            // check write permissions
+            if (!CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
+            {
+                throw new InvalidOperationException("Client is not allowed to write to this NetworkList");
+            }
+
             m_List.Clear();
 
             var listEvent = new NetworkListEvent<T>()
@@ -360,14 +413,20 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public bool Contains(T item)
         {
-            int index = NativeArrayExtensions.IndexOf(m_List, item);
+            int index = m_List.IndexOf(item);
             return index != -1;
         }
 
         /// <inheritdoc />
         public bool Remove(T item)
         {
-            int index = NativeArrayExtensions.IndexOf(m_List, item);
+            // check write permissions
+            if (!CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
+            {
+                throw new InvalidOperationException("Client is not allowed to write to this NetworkList");
+            }
+
+            int index = m_List.IndexOf(item);
             if (index == -1)
             {
                 return false;
@@ -395,9 +454,22 @@ namespace Unity.Netcode
 
         /// <inheritdoc />
         public void Insert(int index, T item)
+        {
+            // check write permissions
+            if (!CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
+            {
+                throw new InvalidOperationException("Client is not allowed to write to this NetworkList");
+            }
+
+            if (index < m_List.Length)
             {
                 m_List.InsertRangeWithBeginEnd(index, index + 1);
                 m_List[index] = item;
+            }
+            else
+            {
+                m_List.Add(item);
+            }
 
             var listEvent = new NetworkListEvent<T>()
             {
@@ -412,6 +484,12 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public void RemoveAt(int index)
         {
+            // check write permissions
+            if (!CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
+            {
+                throw new InvalidOperationException("Client is not allowed to write to this NetworkList");
+            }
+
             m_List.RemoveAt(index);
 
             var listEvent = new NetworkListEvent<T>()
@@ -429,13 +507,21 @@ namespace Unity.Netcode
             get => m_List[index];
             set
             {
+                // check write permissions
+                if (!CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
+                {
+                    throw new InvalidOperationException("Client is not allowed to write to this NetworkList");
+                }
+
+                var previousValue = m_List[index];
                 m_List[index] = value;
 
                 var listEvent = new NetworkListEvent<T>()
                 {
                     Type = NetworkListEvent<T>.EventType.Value,
                     Index = index,
-                    Value = value
+                    Value = value,
+                    PreviousValue = previousValue
                 };
 
                 HandleAddListEvent(listEvent);
@@ -445,9 +531,13 @@ namespace Unity.Netcode
         private void HandleAddListEvent(NetworkListEvent<T> listEvent)
         {
             m_DirtyEvents.Add(listEvent);
+            MarkNetworkObjectDirty();
             OnListChanged?.Invoke(listEvent);
         }
 
+        /// <summary>
+        /// This is actually unused left-over from a previous interface
+        /// </summary>
         public int LastModifiedTick
         {
             get
@@ -457,10 +547,14 @@ namespace Unity.Netcode
             }
         }
 
+        /// <summary>
+        /// Overridden <see cref="IDisposable"/> implementation.
+        /// CAUTION: If you derive from this class and override the <see cref="Dispose"/> method,
+        /// you **must** always invoke the base.Dispose() method!
+        /// </summary>
         public override void Dispose()
         {
             m_List.Dispose();
-            m_ListAtLastReset.Dispose();
             m_DirtyEvents.Dispose();
         }
     }

Runtime/NetworkVariable/NetworkVariable.cs

@@ -1,15 +1,14 @@
 using UnityEngine;
 using System;
-using System.Runtime.CompilerServices;
-using Unity.Collections.LowLevel.Unsafe;
 
 namespace Unity.Netcode
 {
     /// <summary>
     /// A variable that can be synchronized over the network.
     /// </summary>
+    /// <typeparam name="T">the unmanaged type for <see cref="NetworkVariable{T}"/> </typeparam>
     [Serializable]
-    public class NetworkVariable<T> : NetworkVariableBase where T : unmanaged
+    public class NetworkVariable<T> : NetworkVariableBase
     {
         /// <summary>
         /// Delegate type for value changed event
@@ -22,7 +21,12 @@ namespace Unity.Netcode
         /// </summary>
         public OnValueChangedDelegate OnValueChanged;
 
-
+        /// <summary>
+        /// Constructor for <see cref="NetworkVariable{T}"/>
+        /// </summary>
+        /// <param name="value">initial value set that is of type T</param>
+        /// <param name="readPerm">the <see cref="NetworkVariableReadPermission"/> for this <see cref="NetworkVariable{T}"/></param>
+        /// <param name="writePerm">the <see cref="NetworkVariableWritePermission"/> for this <see cref="NetworkVariable{T}"/></param>
         public NetworkVariable(T value = default,
             NetworkVariableReadPermission readPerm = DefaultReadPerm,
             NetworkVariableWritePermission writePerm = DefaultWritePerm)
@@ -31,6 +35,9 @@ namespace Unity.Netcode
             m_InternalValue = value;
         }
 
+        /// <summary>
+        /// The internal value of the NetworkVariable
+        /// </summary>
         [SerializeField]
         private protected T m_InternalValue;
 
@@ -43,7 +50,7 @@ namespace Unity.Netcode
             set
             {
                 // Compare bitwise
-                if (ValueEquals(ref m_InternalValue, ref value))
+                if (NetworkVariableSerialization<T>.AreEqual(ref m_InternalValue, ref value))
                 {
                     return;
                 }
@@ -57,24 +64,14 @@ namespace Unity.Netcode
             }
         }
 
-        // Compares two values of the same unmanaged type by underlying memory
+        /// <summary>
-        // Ignoring any overriden value checks
+        /// Sets the <see cref="Value"/>, marks the <see cref="NetworkVariable{T}"/> dirty, and invokes the <see cref="OnValueChanged"/> callback
-        // Size is fixed
+        /// if there are subscribers to that event.
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        /// </summary>
-        private static unsafe bool ValueEquals(ref T a, ref T b)
+        /// <param name="value">the new value of type `T` to be set/></param>
-        {
-            // get unmanaged pointers
-            var aptr = UnsafeUtility.AddressOf(ref a);
-            var bptr = UnsafeUtility.AddressOf(ref b);
-
-            // compare addresses
-            return UnsafeUtility.MemCmp(aptr, bptr, sizeof(T)) == 0;
-        }
-
-
         private protected void Set(T value)
         {
-            m_IsDirty = true;
+            SetDirty(true);
             T previousValue = m_InternalValue;
             m_InternalValue = value;
             OnValueChanged?.Invoke(previousValue, m_InternalValue);
@@ -102,11 +99,11 @@ namespace Unity.Netcode
             // would be stored in different fields
 
             T previousValue = m_InternalValue;
-            NetworkVariableSerialization<T>.Read(reader, out m_InternalValue);
+            NetworkVariableSerialization<T>.Read(reader, ref m_InternalValue);
 
             if (keepDirtyDelta)
             {
-                m_IsDirty = true;
+                SetDirty(true);
             }
 
             OnValueChanged?.Invoke(previousValue, m_InternalValue);
@@ -115,7 +112,7 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public override void ReadField(FastBufferReader reader)
         {
-            NetworkVariableSerialization<T>.Read(reader, out m_InternalValue);
+            NetworkVariableSerialization<T>.Read(reader, ref m_InternalValue);
         }
 
         /// <inheritdoc />

Runtime/NetworkVariable/NetworkVariableBase.cs

@@ -1,4 +1,5 @@
 using System;
+using UnityEngine;
 
 namespace Unity.Netcode
 {
@@ -12,16 +13,36 @@ namespace Unity.Netcode
         /// </summary>
         internal const NetworkDelivery Delivery = NetworkDelivery.ReliableFragmentedSequenced;
 
+        /// <summary>
+        /// Maintains a link to the associated NetworkBehaviour
+        /// </summary>
         private protected NetworkBehaviour m_NetworkBehaviour;
 
+        /// <summary>
+        /// Initializes the NetworkVariable
+        /// </summary>
+        /// <param name="networkBehaviour">The NetworkBehaviour the NetworkVariable belongs to</param>
         public void Initialize(NetworkBehaviour networkBehaviour)
         {
             m_NetworkBehaviour = networkBehaviour;
         }
 
+        /// <summary>
+        /// The default read permissions
+        /// </summary>
         public const NetworkVariableReadPermission DefaultReadPerm = NetworkVariableReadPermission.Everyone;
+
+        /// <summary>
+        /// The default write permissions
+        /// </summary>
         public const NetworkVariableWritePermission DefaultWritePerm = NetworkVariableWritePermission.Server;
 
+        /// <summary>
+        /// The default constructor for <see cref="NetworkVariableBase"/> that can be used to create a
+        /// custom NetworkVariable.
+        /// </summary>
+        /// <param name="readPerm">the <see cref="NetworkVariableReadPermission"/> access settings</param>
+        /// <param name="writePerm">the <see cref="NetworkVariableWritePermission"/> access settings</param>
         protected NetworkVariableBase(
             NetworkVariableReadPermission readPerm = DefaultReadPerm,
             NetworkVariableWritePermission writePerm = DefaultWritePerm)
@@ -30,7 +51,11 @@ namespace Unity.Netcode
             WritePerm = writePerm;
         }
 
-        private protected bool m_IsDirty;
+        /// <summary>
+        /// The <see cref="m_IsDirty"/> property is used to determine if the
+        /// value of the `NetworkVariable` has changed.
+        /// </summary>
+        private bool m_IsDirty;
 
         /// <summary>
         /// Gets or sets the name of the network variable's instance
@@ -43,14 +68,29 @@ namespace Unity.Netcode
         /// </summary>
         public readonly NetworkVariableReadPermission ReadPerm;
 
+        /// <summary>
+        /// The write permission for this var
+        /// </summary>
         public readonly NetworkVariableWritePermission WritePerm;
 
         /// <summary>
         /// Sets whether or not the variable needs to be delta synced
         /// </summary>
+        /// <param name="isDirty">Whether or not the var is dirty</param>
         public virtual void SetDirty(bool isDirty)
         {
             m_IsDirty = isDirty;
+
+            if (m_IsDirty)
+            {
+                if (m_NetworkBehaviour == null)
+                {
+                    Debug.LogWarning($"NetworkVariable is written to, but doesn't know its NetworkBehaviour yet. " +
+                                     "Are you modifying a NetworkVariable before the NetworkObject is spawned?");
+                    return;
+                }
+                m_NetworkBehaviour.NetworkManager.MarkNetworkObjectDirty(m_NetworkBehaviour.NetworkObject);
+            }
         }
 
         /// <summary>
@@ -70,6 +110,11 @@ namespace Unity.Netcode
             return m_IsDirty;
         }
 
+        /// <summary>
+        /// Gets if a specific client has permission to read the var or not
+        /// </summary>
+        /// <param name="clientId">The client id</param>
+        /// <returns>Whether or not the client has permission to read</returns>
         public bool CanClientRead(ulong clientId)
         {
             switch (ReadPerm)
@@ -78,10 +123,15 @@ namespace Unity.Netcode
                 case NetworkVariableReadPermission.Everyone:
                     return true;
                 case NetworkVariableReadPermission.Owner:
-                    return clientId == m_NetworkBehaviour.NetworkObject.OwnerClientId;
+                    return clientId == m_NetworkBehaviour.NetworkObject.OwnerClientId || NetworkManager.ServerClientId == clientId;
             }
         }
 
+        /// <summary>
+        /// Gets if a specific client has permission to write the var or not
+        /// </summary>
+        /// <param name="clientId">The client id</param>
+        /// <returns>Whether or not the client has permission to write</returns>
         public bool CanClientWrite(ulong clientId)
         {
             switch (WritePerm)
@@ -127,6 +177,9 @@ namespace Unity.Netcode
         /// <param name="keepDirtyDelta">Whether or not the delta should be kept as dirty or consumed</param>
         public abstract void ReadDelta(FastBufferReader reader, bool keepDirtyDelta);
 
+        /// <summary>
+        /// Virtual <see cref="IDisposable"/> implementation
+        /// </summary>
         public virtual void Dispose()
         {
         }

Runtime/NetworkVariable/NetworkVariablePermission.cs

@@ -1,14 +1,32 @@
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// The permission types for reading a var
+    /// </summary>
     public enum NetworkVariableReadPermission
     {
+        /// <summary>
+        /// Everyone can read
+        /// </summary>
         Everyone,
+        /// <summary>
+        /// Only the owner and the server can read
+        /// </summary>
         Owner,
     }
 
+    /// <summary>
+    ///  The permission types for writing a var
+    /// </summary>
     public enum NetworkVariableWritePermission
     {
+        /// <summary>
+        /// Only the server can write
+        /// </summary>
         Server,
+        /// <summary>
+        /// Only the owner can write
+        /// </summary>
         Owner
     }
 }

Runtime/NetworkVariable/NetworkVariableSerialization.cs

@@ -1,6 +1,7 @@
 using System;
-using System.Collections.Generic;
 using Unity.Collections;
+using Unity.Collections.LowLevel.Unsafe;
+using UnityEditor;
 using UnityEngine;
 
 namespace Unity.Netcode
@@ -18,7 +19,97 @@ namespace Unity.Netcode
         // Taking T as an in parameter like we do in other places would require making a copy
         // of it to pass it as a ref parameter.
         public void Write(FastBufferWriter writer, ref T value);
-        public void Read(FastBufferReader reader, out T value);
+        public void Read(FastBufferReader reader, ref T value);
+    }
+
+    /// <summary>
+    /// Packing serializer for shorts
+    /// </summary>
+    internal class ShortSerializer : INetworkVariableSerializer<short>
+    {
+        public void Write(FastBufferWriter writer, ref short value)
+        {
+            BytePacker.WriteValueBitPacked(writer, value);
+        }
+        public void Read(FastBufferReader reader, ref short value)
+        {
+            ByteUnpacker.ReadValueBitPacked(reader, out value);
+        }
+    }
+
+    /// <summary>
+    /// Packing serializer for shorts
+    /// </summary>
+    internal class UshortSerializer : INetworkVariableSerializer<ushort>
+    {
+        public void Write(FastBufferWriter writer, ref ushort value)
+        {
+            BytePacker.WriteValueBitPacked(writer, value);
+        }
+        public void Read(FastBufferReader reader, ref ushort value)
+        {
+            ByteUnpacker.ReadValueBitPacked(reader, out value);
+        }
+    }
+
+    /// <summary>
+    /// Packing serializer for ints
+    /// </summary>
+    internal class IntSerializer : INetworkVariableSerializer<int>
+    {
+        public void Write(FastBufferWriter writer, ref int value)
+        {
+            BytePacker.WriteValueBitPacked(writer, value);
+        }
+        public void Read(FastBufferReader reader, ref int value)
+        {
+            ByteUnpacker.ReadValueBitPacked(reader, out value);
+        }
+    }
+
+    /// <summary>
+    /// Packing serializer for ints
+    /// </summary>
+    internal class UintSerializer : INetworkVariableSerializer<uint>
+    {
+        public void Write(FastBufferWriter writer, ref uint value)
+        {
+            BytePacker.WriteValueBitPacked(writer, value);
+        }
+        public void Read(FastBufferReader reader, ref uint value)
+        {
+            ByteUnpacker.ReadValueBitPacked(reader, out value);
+        }
+    }
+
+    /// <summary>
+    /// Packing serializer for longs
+    /// </summary>
+    internal class LongSerializer : INetworkVariableSerializer<long>
+    {
+        public void Write(FastBufferWriter writer, ref long value)
+        {
+            BytePacker.WriteValueBitPacked(writer, value);
+        }
+        public void Read(FastBufferReader reader, ref long value)
+        {
+            ByteUnpacker.ReadValueBitPacked(reader, out value);
+        }
+    }
+
+    /// <summary>
+    /// Packing serializer for longs
+    /// </summary>
+    internal class UlongSerializer : INetworkVariableSerializer<ulong>
+    {
+        public void Write(FastBufferWriter writer, ref ulong value)
+        {
+            BytePacker.WriteValueBitPacked(writer, value);
+        }
+        public void Read(FastBufferReader reader, ref ulong value)
+        {
+            ByteUnpacker.ReadValueBitPacked(reader, out value);
+        }
     }
 
     /// <summary>
@@ -35,79 +126,80 @@ namespace Unity.Netcode
         {
             writer.WriteUnmanagedSafe(value);
         }
-        public void Read(FastBufferReader reader, out T value)
+        public void Read(FastBufferReader reader, ref T value)
         {
             reader.ReadUnmanagedSafe(out value);
         }
     }
 
     /// <summary>
-    /// Serializer for FixedStrings, which does the same thing FastBufferWriter/FastBufferReader do,
+    /// Serializer for FixedStrings
-    /// but is implemented to get the data it needs using open instance delegates that are passed in
-    /// via reflection. This prevents needing T to meet any interface requirements (which isn't achievable
-    /// without incurring GC allocs on every call to Write or Read - reflection + Open Instance Delegates
-    /// circumvent that.)
-    ///
-    /// Tests show that calling these delegates doesn't cause any GC allocations even though they're
-    /// obtained via reflection and Delegate.CreateDelegate() and called on types that, at compile time,
-    /// aren't known to actually contain those methods.
     /// </summary>
     /// <typeparam name="T"></typeparam>
-    internal class FixedStringSerializer<T> : INetworkVariableSerializer<T> where T : unmanaged
+    internal class FixedStringSerializer<T> : INetworkVariableSerializer<T> where T : unmanaged, INativeList<byte>, IUTF8Bytes
     {
-        internal delegate int GetLengthDelegate(ref T value);
+        public void Write(FastBufferWriter writer, ref T value)
-        internal delegate void SetLengthDelegate(ref T value, int length);
-        internal unsafe delegate byte* GetUnsafePtrDelegate(ref T value);
-
-        internal GetLengthDelegate GetLength;
-        internal SetLengthDelegate SetLength;
-        internal GetUnsafePtrDelegate GetUnsafePtr;
-
-        public unsafe void Write(FastBufferWriter writer, ref T value)
         {
-            int length = GetLength(ref value);
+            writer.WriteValueSafe(value);
-            byte* data = GetUnsafePtr(ref value);
-            writer.WriteUnmanagedSafe(length);
-            writer.WriteBytesSafe(data, length);
         }
-        public unsafe void Read(FastBufferReader reader, out T value)
+        public void Read(FastBufferReader reader, ref T value)
         {
-            value = new T();
+            reader.ReadValueSafeInPlace(ref value);
-            reader.ReadValueSafe(out int length);
-            SetLength(ref value, length);
-            reader.ReadBytesSafe(GetUnsafePtr(ref value), length);
         }
     }
 
     /// <summary>
-    /// Serializer for INetworkSerializable types, which does the same thing
+    /// Serializer for unmanaged INetworkSerializable types
-    /// FastBufferWriter/FastBufferReader do, but is implemented to call the NetworkSerialize() method
-    /// via open instance delegates passed in via reflection. This prevents needing T to meet any interface
-    /// requirements (which isn't achievable without incurring GC allocs on every call to Write or Read -
-    /// reflection + Open Instance Delegates circumvent that.)
-    ///
-    /// Tests show that calling these delegates doesn't cause any GC allocations even though they're
-    /// obtained via reflection and Delegate.CreateDelegate() and called on types that, at compile time,
-    /// aren't known to actually contain those methods.
     /// </summary>
     /// <typeparam name="T"></typeparam>
-    internal class NetworkSerializableSerializer<T> : INetworkVariableSerializer<T> where T : unmanaged
+    internal class UnmanagedNetworkSerializableSerializer<T> : INetworkVariableSerializer<T> where T : unmanaged, INetworkSerializable
     {
-        internal delegate void WriteValueDelegate(ref T value, BufferSerializer<BufferSerializerWriter> serializer);
-        internal delegate void ReadValueDelegate(ref T value, BufferSerializer<BufferSerializerReader> serializer);
-
-        internal WriteValueDelegate WriteValue;
-        internal ReadValueDelegate ReadValue;
         public void Write(FastBufferWriter writer, ref T value)
         {
             var bufferSerializer = new BufferSerializer<BufferSerializerWriter>(new BufferSerializerWriter(writer));
-            WriteValue(ref value, bufferSerializer);
+            value.NetworkSerialize(bufferSerializer);
         }
-        public void Read(FastBufferReader reader, out T value)
+        public void Read(FastBufferReader reader, ref T value)
+        {
+            var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(reader));
+            value.NetworkSerialize(bufferSerializer);
+
+        }
+    }
+
+    /// <summary>
+    /// Serializer for managed INetworkSerializable types, which differs from the unmanaged implementation in that it
+    /// has to be null-aware
+    /// <typeparam name="T"></typeparam>
+    internal class ManagedNetworkSerializableSerializer<T> : INetworkVariableSerializer<T> where T : class, INetworkSerializable, new()
+    {
+        public void Write(FastBufferWriter writer, ref T value)
+        {
+            var bufferSerializer = new BufferSerializer<BufferSerializerWriter>(new BufferSerializerWriter(writer));
+            bool isNull = (value == null);
+            bufferSerializer.SerializeValue(ref isNull);
+            if (!isNull)
+            {
+                value.NetworkSerialize(bufferSerializer);
+            }
+        }
+        public void Read(FastBufferReader reader, ref T value)
+        {
+            var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(reader));
+            bool isNull = false;
+            bufferSerializer.SerializeValue(ref isNull);
+            if (isNull)
+            {
+                value = null;
+            }
+            else
+            {
+                if (value == null)
                 {
                     value = new T();
-            var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(reader));
+                }
-            ReadValue(ref value, bufferSerializer);
+                value.NetworkSerialize(bufferSerializer);
+            }
         }
     }
 
@@ -120,10 +212,28 @@ namespace Unity.Netcode
     /// <typeparam name="T"></typeparam>
     public class UserNetworkVariableSerialization<T>
     {
+        /// <summary>
+        /// The write value delegate handler definition
+        /// </summary>
+        /// <param name="writer">The <see cref="FastBufferWriter"/> to write the value of type `T`</param>
+        /// <param name="value">The value of type `T` to be written</param>
         public delegate void WriteValueDelegate(FastBufferWriter writer, in T value);
+
+        /// <summary>
+        /// The read value delegate handler definition
+        /// </summary>
+        /// <param name="reader">The <see cref="FastBufferReader"/> to read the value of type `T`</param>
+        /// <param name="value">The value of type `T` to be read</param>
         public delegate void ReadValueDelegate(FastBufferReader reader, out T value);
 
+        /// <summary>
+        /// The <see cref="WriteValueDelegate"/> delegate handler declaration
+        /// </summary>
         public static WriteValueDelegate WriteValue;
+
+        /// <summary>
+        /// The <see cref="ReadValueDelegate"/> delegate handler declaration
+        /// </summary>
         public static ReadValueDelegate ReadValue;
     }
 
@@ -146,7 +256,7 @@ namespace Unity.Netcode
             }
             UserNetworkVariableSerialization<T>.WriteValue(writer, value);
         }
-        public void Read(FastBufferReader reader, out T value)
+        public void Read(FastBufferReader reader, ref T value)
         {
             if (UserNetworkVariableSerialization<T>.ReadValue == null || UserNetworkVariableSerialization<T>.WriteValue == null)
             {
@@ -156,34 +266,115 @@ namespace Unity.Netcode
         }
     }
 
-    internal static class NetworkVariableSerializationTypes
+    /// <summary>
+    /// This class contains initialization functions for various different types used in NetworkVariables.
+    /// Generally speaking, these methods are called by a module initializer created by codegen (NetworkBehaviourILPP)
+    /// and do not need to be called manually.
+    ///
+    /// There are two types of initializers: Serializers and EqualityCheckers. Every type must have an EqualityChecker
+    /// registered to it in order to be used in NetworkVariable; however, not all types need a Serializer. Types without
+    /// a serializer registered will fall back to using the delegates in <see cref="UserNetworkVariableSerialization{T}"/>.
+    /// If no such delegate has been registered, a type without a serializer will throw an exception on the first attempt
+    /// to serialize or deserialize it. (Again, however, codegen handles this automatically and this registration doesn't
+    /// typically need to be performed manually.)
+    /// </summary>
+    public static class NetworkVariableSerializationTypes
     {
-        internal static readonly HashSet<Type> BaseSupportedTypes = new HashSet<Type>
+        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterAssembliesLoaded)]
+#if UNITY_EDITOR
+        [InitializeOnLoadMethod]
+#endif
+        internal static void InitializeIntegerSerialization()
         {
-            typeof(bool),
+            NetworkVariableSerialization<short>.Serializer = new ShortSerializer();
-            typeof(byte),
+            NetworkVariableSerialization<short>.AreEqual = NetworkVariableSerialization<short>.ValueEquals;
-            typeof(sbyte),
+            NetworkVariableSerialization<ushort>.Serializer = new UshortSerializer();
-            typeof(char),
+            NetworkVariableSerialization<ushort>.AreEqual = NetworkVariableSerialization<ushort>.ValueEquals;
-            typeof(decimal),
+            NetworkVariableSerialization<int>.Serializer = new IntSerializer();
-            typeof(double),
+            NetworkVariableSerialization<int>.AreEqual = NetworkVariableSerialization<int>.ValueEquals;
-            typeof(float),
+            NetworkVariableSerialization<uint>.Serializer = new UintSerializer();
-            typeof(int),
+            NetworkVariableSerialization<uint>.AreEqual = NetworkVariableSerialization<uint>.ValueEquals;
-            typeof(uint),
+            NetworkVariableSerialization<long>.Serializer = new LongSerializer();
-            typeof(long),
+            NetworkVariableSerialization<long>.AreEqual = NetworkVariableSerialization<long>.ValueEquals;
-            typeof(ulong),
+            NetworkVariableSerialization<ulong>.Serializer = new UlongSerializer();
-            typeof(short),
+            NetworkVariableSerialization<ulong>.AreEqual = NetworkVariableSerialization<ulong>.ValueEquals;
-            typeof(ushort),
+        }
-            typeof(Vector2),
+
-            typeof(Vector3),
+        /// <summary>
-            typeof(Vector2Int),
+        /// Registeres an unmanaged type that will be serialized by a direct memcpy into a buffer
-            typeof(Vector3Int),
+        /// </summary>
-            typeof(Vector4),
+        /// <typeparam name="T"></typeparam>
-            typeof(Quaternion),
+        public static void InitializeSerializer_UnmanagedByMemcpy<T>() where T : unmanaged
-            typeof(Color),
+        {
-            typeof(Color32),
+            NetworkVariableSerialization<T>.Serializer = new UnmanagedTypeSerializer<T>();
-            typeof(Ray),
+        }
-            typeof(Ray2D)
+
-        };
+        /// <summary>
+        /// Registers an unmanaged type that implements INetworkSerializable and will be serialized through a call to
+        /// NetworkSerialize
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeSerializer_UnmanagedINetworkSerializable<T>() where T : unmanaged, INetworkSerializable
+        {
+            NetworkVariableSerialization<T>.Serializer = new UnmanagedNetworkSerializableSerializer<T>();
+        }
+
+        /// <summary>
+        /// Registers a managed type that implements INetworkSerializable and will be serialized through a call to
+        /// NetworkSerialize
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeSerializer_ManagedINetworkSerializable<T>() where T : class, INetworkSerializable, new()
+        {
+            NetworkVariableSerialization<T>.Serializer = new ManagedNetworkSerializableSerializer<T>();
+        }
+
+        /// <summary>
+        /// Registers a FixedString type that will be serialized through FastBufferReader/FastBufferWriter's FixedString
+        /// serializers
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeSerializer_FixedString<T>() where T : unmanaged, INativeList<byte>, IUTF8Bytes
+        {
+            NetworkVariableSerialization<T>.Serializer = new FixedStringSerializer<T>();
+        }
+
+        /// <summary>
+        /// Registers a managed type that will be checked for equality using T.Equals()
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeEqualityChecker_ManagedIEquatable<T>() where T : class, IEquatable<T>
+        {
+            NetworkVariableSerialization<T>.AreEqual = NetworkVariableSerialization<T>.EqualityEqualsObject;
+        }
+
+        /// <summary>
+        /// Registers an unmanaged type that will be checked for equality using T.Equals()
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeEqualityChecker_UnmanagedIEquatable<T>() where T : unmanaged, IEquatable<T>
+        {
+            NetworkVariableSerialization<T>.AreEqual = NetworkVariableSerialization<T>.EqualityEquals;
+        }
+
+        /// <summary>
+        /// Registers an unmanaged type that will be checked for equality using memcmp and only considered
+        /// equal if they are bitwise equivalent in memory
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeEqualityChecker_UnmanagedValueEquals<T>() where T : unmanaged
+        {
+            NetworkVariableSerialization<T>.AreEqual = NetworkVariableSerialization<T>.ValueEquals;
+        }
+
+        /// <summary>
+        /// Registers a managed type that will be checked for equality using the == operator
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeEqualityChecker_ManagedClassEquals<T>() where T : class
+        {
+            NetworkVariableSerialization<T>.AreEqual = NetworkVariableSerialization<T>.ClassEquals;
+        }
     }
 
     /// <summary>
@@ -192,57 +383,61 @@ namespace Unity.Netcode
     /// but there's no way to achieve the same thing with a class, this sets up various read/write schemes
     /// based on which constraints are met by `T` using reflection, which is done at module load time.
     /// </summary>
+    /// <typeparam name="T">The type the associated NetworkVariable is templated on</typeparam>
     [Serializable]
-    public static class NetworkVariableSerialization<T> where T : unmanaged
+    public static class NetworkVariableSerialization<T>
     {
-        private static INetworkVariableSerializer<T> s_Serializer = GetSerializer();
+        internal static INetworkVariableSerializer<T> Serializer = new FallbackSerializer<T>();
 
-        private static INetworkVariableSerializer<T> GetSerializer()
+        internal delegate bool EqualsDelegate(ref T a, ref T b);
+        internal static EqualsDelegate AreEqual;
+
+        // Compares two values of the same unmanaged type by underlying memory
+        // Ignoring any overridden value checks
+        // Size is fixed
+        internal static unsafe bool ValueEquals<TValueType>(ref TValueType a, ref TValueType b) where TValueType : unmanaged
         {
-            if (NetworkVariableSerializationTypes.BaseSupportedTypes.Contains(typeof(T)))
+            // get unmanaged pointers
-            {
+            var aptr = UnsafeUtility.AddressOf(ref a);
-                return new UnmanagedTypeSerializer<T>();
+            var bptr = UnsafeUtility.AddressOf(ref b);
-            }
+
-            if (typeof(INetworkSerializeByMemcpy).IsAssignableFrom(typeof(T)))
+            // compare addresses
-            {
+            return UnsafeUtility.MemCmp(aptr, bptr, sizeof(TValueType)) == 0;
-                return new UnmanagedTypeSerializer<T>();
-            }
-            if (typeof(Enum).IsAssignableFrom(typeof(T)))
-            {
-                return new UnmanagedTypeSerializer<T>();
         }
 
-            if (typeof(INetworkSerializable).IsAssignableFrom(typeof(T)))
+        internal static bool EqualityEqualsObject<TValueType>(ref TValueType a, ref TValueType b) where TValueType : class, IEquatable<TValueType>
         {
-                // Obtains "Open Instance Delegates" for the type's NetworkSerialize() methods -
+            if (a == null)
-                // one for an instance of the generic method taking BufferSerializerWriter as T,
+            {
-                // one for an instance of the generic method taking BufferSerializerReader as T
+                return b == null;
-                var writeMethod = (NetworkSerializableSerializer<T>.WriteValueDelegate)Delegate.CreateDelegate(typeof(NetworkSerializableSerializer<T>.WriteValueDelegate), null, typeof(T).GetMethod(nameof(INetworkSerializable.NetworkSerialize)).MakeGenericMethod(typeof(BufferSerializerWriter)));
-                var readMethod = (NetworkSerializableSerializer<T>.ReadValueDelegate)Delegate.CreateDelegate(typeof(NetworkSerializableSerializer<T>.ReadValueDelegate), null, typeof(T).GetMethod(nameof(INetworkSerializable.NetworkSerialize)).MakeGenericMethod(typeof(BufferSerializerReader)));
-                return new NetworkSerializableSerializer<T> { WriteValue = writeMethod, ReadValue = readMethod };
             }
 
-            if (typeof(IUTF8Bytes).IsAssignableFrom(typeof(T)) && typeof(INativeList<byte>).IsAssignableFrom(typeof(T)))
+            if (b == null)
             {
-                // Get "OpenInstanceDelegates" for the Length property (get and set, which are prefixed
+                return false;
-                // with "get_" and "set_" under the hood and emitted as methods) and GetUnsafePtr()
-                var getLength = (FixedStringSerializer<T>.GetLengthDelegate)Delegate.CreateDelegate(typeof(FixedStringSerializer<T>.GetLengthDelegate), null, typeof(T).GetMethod("get_" + nameof(INativeList<byte>.Length)));
-                var setLength = (FixedStringSerializer<T>.SetLengthDelegate)Delegate.CreateDelegate(typeof(FixedStringSerializer<T>.SetLengthDelegate), null, typeof(T).GetMethod("set_" + nameof(INativeList<byte>.Length)));
-                var getUnsafePtr = (FixedStringSerializer<T>.GetUnsafePtrDelegate)Delegate.CreateDelegate(typeof(FixedStringSerializer<T>.GetUnsafePtrDelegate), null, typeof(T).GetMethod(nameof(IUTF8Bytes.GetUnsafePtr)));
-                return new FixedStringSerializer<T> { GetLength = getLength, SetLength = setLength, GetUnsafePtr = getUnsafePtr };
             }
 
-            return new FallbackSerializer<T>();
+            return a.Equals(b);
+        }
+
+        internal static bool EqualityEquals<TValueType>(ref TValueType a, ref TValueType b) where TValueType : unmanaged, IEquatable<TValueType>
+        {
+            return a.Equals(b);
+        }
+
+        internal static bool ClassEquals<TValueType>(ref TValueType a, ref TValueType b) where TValueType : class
+        {
+            return a == b;
         }
 
         internal static void Write(FastBufferWriter writer, ref T value)
         {
-            s_Serializer.Write(writer, ref value);
+            Serializer.Write(writer, ref value);
         }
 
-        internal static void Read(FastBufferReader reader, out T value)
+        internal static void Read(FastBufferReader reader, ref T value)
         {
-            s_Serializer.Read(reader, out value);
+            Serializer.Read(reader, ref value);
         }
     }
 }

Runtime/SceneManagement/ISceneManagerHandler.cs

@@ -1,4 +1,3 @@
-using System;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
@@ -10,25 +9,8 @@ namespace Unity.Netcode
     /// </summary>
     internal interface ISceneManagerHandler
     {
-        // Generic action to call when a scene is finished loading/unloading
+        AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, SceneEventProgress sceneEventProgress);
-        struct SceneEventAction
-        {
-            internal uint SceneEventId;
-            internal Action<uint> EventAction;
-            /// <summary>
-            /// Used server-side for integration testing in order to
-            /// invoke the SceneEventProgress once done loading
-            /// </summary>
-            internal Action Completed;
-            internal void Invoke()
-            {
-                Completed?.Invoke();
-                EventAction.Invoke(SceneEventId);
-            }
-        }
 
-        AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, SceneEventAction sceneEventAction);
+        AsyncOperation UnloadSceneAsync(Scene scene, SceneEventProgress sceneEventProgress);
-
-        AsyncOperation UnloadSceneAsync(Scene scene, SceneEventAction sceneEventAction);
     }
 }

Runtime/SceneManagement/NetworkSceneManager.cs

@@ -338,17 +338,17 @@ namespace Unity.Netcode
         /// </summary>
         private class DefaultSceneManagerHandler : ISceneManagerHandler
         {
-            public AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, ISceneManagerHandler.SceneEventAction sceneEventAction)
+            public AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, SceneEventProgress sceneEventProgress)
             {
                 var operation = SceneManager.LoadSceneAsync(sceneName, loadSceneMode);
-                operation.completed += new Action<AsyncOperation>(asyncOp2 => { sceneEventAction.Invoke(); });
+                sceneEventProgress.SetAsyncOperation(operation);
                 return operation;
             }
 
-            public AsyncOperation UnloadSceneAsync(Scene scene, ISceneManagerHandler.SceneEventAction sceneEventAction)
+            public AsyncOperation UnloadSceneAsync(Scene scene, SceneEventProgress sceneEventProgress)
             {
                 var operation = SceneManager.UnloadSceneAsync(scene);
-                operation.completed += new Action<AsyncOperation>(asyncOp2 => { sceneEventAction.Invoke(); });
+                sceneEventProgress.SetAsyncOperation(operation);
                 return operation;
             }
         }
@@ -887,12 +887,14 @@ namespace Unity.Netcode
         private bool OnSceneEventProgressCompleted(SceneEventProgress sceneEventProgress)
         {
             var sceneEventData = BeginSceneEvent();
+            var clientsThatCompleted = sceneEventProgress.GetClientsWithStatus(true);
+            var clientsThatTimedOut = sceneEventProgress.GetClientsWithStatus(false);
             sceneEventData.SceneEventProgressId = sceneEventProgress.Guid;
             sceneEventData.SceneHash = sceneEventProgress.SceneHash;
             sceneEventData.SceneEventType = sceneEventProgress.SceneEventType;
-            sceneEventData.ClientsCompleted = sceneEventProgress.DoneClients;
+            sceneEventData.ClientsCompleted = clientsThatCompleted;
             sceneEventData.LoadSceneMode = sceneEventProgress.LoadSceneMode;
-            sceneEventData.ClientsTimedOut = sceneEventProgress.ClientsThatStartedSceneEvent.Except(sceneEventProgress.DoneClients).ToList();
+            sceneEventData.ClientsTimedOut = clientsThatTimedOut;
 
             var message = new SceneEventMessage
             {
@@ -913,8 +915,8 @@ namespace Unity.Netcode
                 SceneName = SceneNameFromHash(sceneEventProgress.SceneHash),
                 ClientId = NetworkManager.ServerClientId,
                 LoadSceneMode = sceneEventProgress.LoadSceneMode,
-                ClientsThatCompleted = sceneEventProgress.DoneClients,
+                ClientsThatCompleted = clientsThatCompleted,
-                ClientsThatTimedOut = m_NetworkManager.ConnectedClients.Keys.Except(sceneEventProgress.DoneClients).ToList(),
+                ClientsThatTimedOut = clientsThatTimedOut,
             });
 
             if (sceneEventData.SceneEventType == SceneEventType.LoadEventCompleted)
@@ -935,7 +937,7 @@ namespace Unity.Netcode
         /// Unloads an additively loaded scene.  If you want to unload a <see cref="LoadSceneMode.Single"/> mode loaded scene load another <see cref="LoadSceneMode.Single"/> scene.
         /// When applicable, the <see cref="AsyncOperation"/> is delivered within the <see cref="SceneEvent"/> via the <see cref="OnSceneEvent"/>
         /// </summary>
-        /// <param name="sceneName">scene name to unload</param>
+        /// <param name="scene"></param>
         /// <returns><see cref="SceneEventProgressStatus"/> (<see cref="SceneEventProgressStatus.Started"/> means it was successful)</returns>
         public SceneEventProgressStatus UnloadScene(Scene scene)
         {
@@ -969,18 +971,9 @@ namespace Unity.Netcode
             sceneEventProgress.SceneEventType = SceneEventType.UnloadEventCompleted;
 
             ScenesLoaded.Remove(scene.handle);
-            var sceneEventAction = new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventData.SceneEventId, EventAction = OnSceneUnloaded };
+            sceneEventProgress.SceneEventId = sceneEventData.SceneEventId;
-            var sceneUnload = SceneManagerHandler.UnloadSceneAsync(scene, sceneEventAction);
+            sceneEventProgress.OnSceneEventCompleted = OnSceneUnloaded;
-
+            var sceneUnload = SceneManagerHandler.UnloadSceneAsync(scene, sceneEventProgress);
-            // If integration testing, IntegrationTestSceneHandler returns null
-            if (sceneUnload == null)
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneEventAction);
-            }
-            else
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneUnload);
-            }
 
             // Notify local server that a scene is going to be unloaded
             OnSceneEvent?.Invoke(new SceneEvent()
@@ -1024,9 +1017,10 @@ namespace Unity.Netcode
                     $"because the client scene handle {sceneHandle} was not found in ScenesLoaded!");
             }
             m_IsSceneEventActive = true;
-
+            var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
-            var sceneUnload = SceneManagerHandler.UnloadSceneAsync(ScenesLoaded[sceneHandle],
+            sceneEventProgress.SceneEventId = sceneEventData.SceneEventId;
-                new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventData.SceneEventId, EventAction = OnSceneUnloaded });
+            sceneEventProgress.OnSceneEventCompleted = OnSceneUnloaded;
+            var sceneUnload = SceneManagerHandler.UnloadSceneAsync(ScenesLoaded[sceneHandle], sceneEventProgress);
 
             ScenesLoaded.Remove(sceneHandle);
 
@@ -1070,7 +1064,7 @@ namespace Unity.Netcode
                 //Only if we are a host do we want register having loaded for the associated SceneEventProgress
                 if (SceneEventProgressTracking.ContainsKey(sceneEventData.SceneEventProgressId) && m_NetworkManager.IsHost)
                 {
-                    SceneEventProgressTracking[sceneEventData.SceneEventProgressId].AddClientAsDone(NetworkManager.ServerClientId);
+                    SceneEventProgressTracking[sceneEventData.SceneEventProgressId].ClientFinishedSceneEvent(NetworkManager.ServerClientId);
                 }
             }
 
@@ -1119,8 +1113,10 @@ namespace Unity.Netcode
                 // Validate the scene as well as ignore the DDOL (which will have a negative buildIndex)
                 if (currentActiveScene.name != keyHandleEntry.Value.name && keyHandleEntry.Value.buildIndex >= 0)
                 {
-                    var sceneUnload = SceneManagerHandler.UnloadSceneAsync(keyHandleEntry.Value,
+                    var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
-                        new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = EmptySceneUnloadedOperation });
+                    sceneEventProgress.SceneEventId = sceneEventId;
+                    sceneEventProgress.OnSceneEventCompleted = EmptySceneUnloadedOperation;
+                    var sceneUnload = SceneManagerHandler.UnloadSceneAsync(keyHandleEntry.Value, sceneEventProgress);
                     SceneUnloadEventHandler.RegisterScene(this, keyHandleEntry.Value, LoadSceneMode.Additive, sceneUnload);
                 }
             }
@@ -1134,6 +1130,7 @@ namespace Unity.Netcode
         /// When applicable, the <see cref="AsyncOperation"/> is delivered within the <see cref="SceneEvent"/> via <see cref="OnSceneEvent"/>
         /// </summary>
         /// <param name="sceneName">the name of the scene to be loaded</param>
+        /// <param name="loadSceneMode">how the scene will be loaded (single or additive mode)</param>
         /// <returns><see cref="SceneEventProgressStatus"/> (<see cref="SceneEventProgressStatus.Started"/> means it was successful)</returns>
         public SceneEventProgressStatus LoadScene(string sceneName, LoadSceneMode loadSceneMode)
         {
@@ -1179,18 +1176,9 @@ namespace Unity.Netcode
             }
 
             // Now start loading the scene
-            var sceneEventAction = new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = OnSceneLoaded };
+            sceneEventProgress.SceneEventId = sceneEventId;
-            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode, sceneEventAction);
+            sceneEventProgress.OnSceneEventCompleted = OnSceneLoaded;
-            // If integration testing, IntegrationTestSceneHandler returns null
+            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode, sceneEventProgress);
-            if (sceneLoad == null)
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneEventAction);
-            }
-            else
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneLoad);
-            }
-
             // Notify the local server that a scene loading event has begun
             OnSceneEvent?.Invoke(new SceneEvent()
             {
@@ -1354,9 +1342,10 @@ namespace Unity.Netcode
                 SceneUnloadEventHandler.RegisterScene(this, SceneManager.GetActiveScene(), LoadSceneMode.Single);
 
             }
-
+            var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
-            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, sceneEventData.LoadSceneMode,
+            sceneEventProgress.SceneEventId = sceneEventId;
-                new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = OnSceneLoaded });
+            sceneEventProgress.OnSceneEventCompleted = OnSceneLoaded;
+            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, sceneEventData.LoadSceneMode, sceneEventProgress);
 
             OnSceneEvent?.Invoke(new SceneEvent()
             {
@@ -1452,6 +1441,9 @@ namespace Unity.Netcode
                 }
             }
 
+            // Add any despawned when spawned in-scene placed NetworkObjects to the scene event data
+            sceneEventData.AddDespawnedInSceneNetworkObjects();
+
             // Set the server's scene's handle so the client can build a look up table
             sceneEventData.SceneHandle = scene.handle;
 
@@ -1487,7 +1479,7 @@ namespace Unity.Netcode
             //Second, only if we are a host do we want register having loaded for the associated SceneEventProgress
             if (SceneEventProgressTracking.ContainsKey(sceneEventData.SceneEventProgressId) && m_NetworkManager.IsHost)
             {
-                SceneEventProgressTracking[sceneEventData.SceneEventProgressId].AddClientAsDone(NetworkManager.ServerClientId);
+                SceneEventProgressTracking[sceneEventData.SceneEventProgressId].ClientFinishedSceneEvent(NetworkManager.ServerClientId);
             }
             EndSceneEvent(sceneEventId);
         }
@@ -1661,8 +1653,10 @@ namespace Unity.Netcode
             if (!shouldPassThrough)
             {
                 // If not, then load the scene
-                sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode,
+                var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
-                new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = ClientLoadedSynchronization });
+                sceneEventProgress.SceneEventId = sceneEventId;
+                sceneEventProgress.OnSceneEventCompleted = ClientLoadedSynchronization;
+                sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode, sceneEventProgress);
 
                 // Notify local client that a scene load has begun
                 OnSceneEvent?.Invoke(new SceneEvent()
@@ -1879,7 +1873,7 @@ namespace Unity.Netcode
 
                         if (SceneEventProgressTracking.ContainsKey(sceneEventData.SceneEventProgressId))
                         {
-                            SceneEventProgressTracking[sceneEventData.SceneEventProgressId].AddClientAsDone(clientId);
+                            SceneEventProgressTracking[sceneEventData.SceneEventProgressId].ClientFinishedSceneEvent(clientId);
                         }
                         EndSceneEvent(sceneEventId);
                         break;
@@ -1888,7 +1882,7 @@ namespace Unity.Netcode
                     {
                         if (SceneEventProgressTracking.ContainsKey(sceneEventData.SceneEventProgressId))
                         {
-                            SceneEventProgressTracking[sceneEventData.SceneEventProgressId].AddClientAsDone(clientId);
+                            SceneEventProgressTracking[sceneEventData.SceneEventProgressId].ClientFinishedSceneEvent(clientId);
                         }
                         // Notify the local server that the client has finished unloading a scene
                         OnSceneEvent?.Invoke(new SceneEvent()
@@ -2024,7 +2018,11 @@ namespace Unity.Netcode
                 ScenePlacedObjects.Clear();
             }
 
+#if UNITY_2023_1_OR_NEWER
+            var networkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID);
+#else
             var networkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>();
+#endif
 
             // Just add every NetworkObject found that isn't already in the list
             // With additive scenes, we can have multiple in-scene placed NetworkObjects with the same GlobalObjectIdHash value

Runtime/SceneManagement/SceneEventData.cs

@@ -243,13 +243,38 @@ namespace Unity.Netcode
                     m_NetworkObjectsSync.Add(sobj);
                 }
             }
+
+            // Sort by parents before children
+            m_NetworkObjectsSync.Sort(SortParentedNetworkObjects);
+
+            // Sort by INetworkPrefabInstanceHandler implementation before the
+            // NetworkObjects spawned by the implementation
             m_NetworkObjectsSync.Sort(SortNetworkObjects);
+
+            // This is useful to know what NetworkObjects a client is going to be synchronized with
+            // as well as the order in which they will be deserialized
+            if (m_NetworkManager.LogLevel == LogLevel.Developer)
+            {
+                var messageBuilder = new System.Text.StringBuilder(0xFFFF);
+                messageBuilder.Append("[Server-Side Client-Synchronization] NetworkObject serialization order:");
+                foreach (var networkObject in m_NetworkObjectsSync)
+                {
+                    messageBuilder.Append($"{networkObject.name}");
+                }
+                NetworkLog.LogInfo(messageBuilder.ToString());
+            }
         }
 
         internal void AddDespawnedInSceneNetworkObjects()
         {
             m_DespawnedInSceneObjectsSync.Clear();
-            var inSceneNetworkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>().Where((c) => c.NetworkManager == m_NetworkManager);
+            // Find all active and non-active in-scene placed NetworkObjects
+#if UNITY_2023_1_OR_NEWER
+            var inSceneNetworkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(UnityEngine.FindObjectsInactive.Include, UnityEngine.FindObjectsSortMode.InstanceID).Where((c) => c.NetworkManager == m_NetworkManager);
+#else
+            var inSceneNetworkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>(includeInactive: true).Where((c) => c.NetworkManager == m_NetworkManager);
+
+#endif
             foreach (var sobj in inSceneNetworkObjects)
             {
                 if (sobj.IsSceneObject.HasValue && sobj.IsSceneObject.Value && !sobj.IsSpawned)
@@ -323,6 +348,32 @@ namespace Unity.Netcode
             return 0;
         }
 
+        /// <summary>
+        /// Sorts the synchronization order of the NetworkObjects to be serialized
+        /// by parents before children.
+        /// </summary>
+        /// <remarks>
+        /// This only handles late joining players. Spawning and nesting several children
+        /// dynamically is still handled by the orphaned child list when deserialized out of
+        /// hierarchical order (i.e. Spawn parent and child dynamically, parent message is
+        /// dropped and re-sent but child object is received and processed)
+        /// </remarks>
+        private int SortParentedNetworkObjects(NetworkObject first, NetworkObject second)
+        {
+            // If the first has a parent, move the first down
+            if (first.transform.parent != null)
+            {
+                return 1;
+            }
+            else // If the second has a parent and the first does not, then move the first up
+            if (second.transform.parent != null)
+            {
+                return -1;
+            }
+            return 0;
+        }
+
+
         /// <summary>
         /// Client and Server Side:
         /// Serializes data based on the SceneEvent type (<see cref="SceneEventType"/>)
@@ -334,7 +385,7 @@ namespace Unity.Netcode
             writer.WriteValueSafe(SceneEventType);
 
             // Write the scene loading mode
-            writer.WriteValueSafe(LoadSceneMode);
+            writer.WriteValueSafe((byte)LoadSceneMode);
 
             // Write the scene event progress Guid
             if (SceneEventType != SceneEventType.Synchronize)
@@ -398,27 +449,26 @@ namespace Unity.Netcode
             int totalBytes = 0;
 
             // Write the number of NetworkObjects we are serializing
-            BytePacker.WriteValuePacked(writer, m_NetworkObjectsSync.Count());
+            writer.WriteValueSafe(m_NetworkObjectsSync.Count);
+
             // Serialize all NetworkObjects that are spawned
-            for (var i = 0; i < m_NetworkObjectsSync.Count(); ++i)
+            for (var i = 0; i < m_NetworkObjectsSync.Count; ++i)
             {
                 var noStart = writer.Position;
                 var sceneObject = m_NetworkObjectsSync[i].GetMessageSceneObject(TargetClientId);
-                BytePacker.WriteValuePacked(writer, m_NetworkObjectsSync[i].GetSceneOriginHandle());
                 sceneObject.Serialize(writer);
                 var noStop = writer.Position;
                 totalBytes += (int)(noStop - noStart);
             }
 
             // Write the number of despawned in-scene placed NetworkObjects
-            writer.WriteValueSafe(m_DespawnedInSceneObjectsSync.Count());
+            writer.WriteValueSafe(m_DespawnedInSceneObjectsSync.Count);
             // Write the scene handle and GlobalObjectIdHash value
-            for (var i = 0; i < m_DespawnedInSceneObjectsSync.Count(); ++i)
+            for (var i = 0; i < m_DespawnedInSceneObjectsSync.Count; ++i)
             {
                 var noStart = writer.Position;
-                var sceneObject = m_DespawnedInSceneObjectsSync[i].GetMessageSceneObject(TargetClientId);
+                writer.WriteValueSafe(m_DespawnedInSceneObjectsSync[i].GetSceneOriginHandle());
-                BytePacker.WriteValuePacked(writer, m_DespawnedInSceneObjectsSync[i].GetSceneOriginHandle());
+                writer.WriteValueSafe(m_DespawnedInSceneObjectsSync[i].GlobalObjectIdHash);
-                BytePacker.WriteValuePacked(writer, m_DespawnedInSceneObjectsSync[i].GlobalObjectIdHash);
                 var noStop = writer.Position;
                 totalBytes += (int)(noStop - noStart);
             }
@@ -452,8 +502,6 @@ namespace Unity.Netcode
                 {
                     if (keyValuePairBySceneHandle.Value.Observers.Contains(TargetClientId))
                     {
-                        // Write our server relative scene handle for the NetworkObject being serialized
-                        writer.WriteValueSafe(keyValuePairBySceneHandle.Key);
                         // Serialize the NetworkObject
                         var sceneObject = keyValuePairBySceneHandle.Value.GetMessageSceneObject(TargetClientId);
                         sceneObject.Serialize(writer);
@@ -462,6 +510,15 @@ namespace Unity.Netcode
                 }
             }
 
+            // Write the number of despawned in-scene placed NetworkObjects
+            writer.WriteValueSafe(m_DespawnedInSceneObjectsSync.Count);
+            // Write the scene handle and GlobalObjectIdHash value
+            for (var i = 0; i < m_DespawnedInSceneObjectsSync.Count; ++i)
+            {
+                writer.WriteValueSafe(m_DespawnedInSceneObjectsSync[i].GetSceneOriginHandle());
+                writer.WriteValueSafe(m_DespawnedInSceneObjectsSync[i].GlobalObjectIdHash);
+            }
+
             var tailPosition = writer.Position;
             // Reposition to our count position to the head before we wrote our object count
             writer.Seek(headPosition);
@@ -479,7 +536,8 @@ namespace Unity.Netcode
         internal void Deserialize(FastBufferReader reader)
         {
             reader.ReadValueSafe(out SceneEventType);
-            reader.ReadValueSafe(out LoadSceneMode);
+            reader.ReadValueSafe(out byte loadSceneMode);
+            LoadSceneMode = (LoadSceneMode)loadSceneMode;
 
             if (SceneEventType != SceneEventType.Synchronize)
             {
@@ -570,15 +628,19 @@ namespace Unity.Netcode
 
                 for (ushort i = 0; i < newObjectsCount; i++)
                 {
-                    InternalBuffer.ReadValueSafe(out int sceneHandle);
-                    // Set our relative scene to the NetworkObject
-                    m_NetworkManager.SceneManager.SetTheSceneBeingSynchronized(sceneHandle);
-
-                    // Deserialize the NetworkObject
                     var sceneObject = new NetworkObject.SceneObject();
                     sceneObject.Deserialize(InternalBuffer);
+
+                    if (sceneObject.IsSceneObject)
+                    {
+                        // Set our relative scene to the NetworkObject
+                        m_NetworkManager.SceneManager.SetTheSceneBeingSynchronized(sceneObject.NetworkSceneHandle);
+                    }
+
                     NetworkObject.AddSceneObject(sceneObject, InternalBuffer, m_NetworkManager);
                 }
+                // Now deserialize the despawned in-scene placed NetworkObjects list (if any)
+                DeserializeDespawnedInScenePlacedNetworkObjects();
             }
             finally
             {
@@ -600,7 +662,11 @@ namespace Unity.Netcode
 
             if (networkObjectsToRemove.Length > 0)
             {
+#if UNITY_2023_1_OR_NEWER
+                var networkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(UnityEngine.FindObjectsSortMode.InstanceID);
+#else
                 var networkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>();
+#endif
                 var networkObjectIdToNetworkObject = new Dictionary<ulong, NetworkObject>();
                 foreach (var networkObject in networkObjects)
                 {
@@ -702,38 +768,11 @@ namespace Unity.Netcode
         }
 
         /// <summary>
-        /// Client Side:
+        /// For synchronizing any despawned in-scene placed NetworkObjects that were
-        /// During the processing of a server sent Event_Sync, this method will be called for each scene once
+        /// despawned by the server during synchronization or scene loading
-        /// it is finished loading.  The client will also build a list of NetworkObjects that it spawned during
-        /// this process which will be used as part of the Event_Sync_Complete response.
         /// </summary>
-        /// <param name="networkManager"></param>
+        private void DeserializeDespawnedInScenePlacedNetworkObjects()
-        internal void SynchronizeSceneNetworkObjects(NetworkManager networkManager)
         {
-            try
-            {
-                // Process all spawned NetworkObjects for this network session
-                ByteUnpacker.ReadValuePacked(InternalBuffer, out int newObjectsCount);
-
-
-                for (int i = 0; i < newObjectsCount; i++)
-                {
-                    // We want to make sure for each NetworkObject we have the appropriate scene selected as the scene that is
-                    // currently being synchronized.  This assures in-scene placed NetworkObjects will use the right NetworkObject
-                    // from the list of populated <see cref="NetworkSceneManager.ScenePlacedObjects"/>
-                    ByteUnpacker.ReadValuePacked(InternalBuffer, out int handle);
-                    m_NetworkManager.SceneManager.SetTheSceneBeingSynchronized(handle);
-
-                    var sceneObject = new NetworkObject.SceneObject();
-                    sceneObject.Deserialize(InternalBuffer);
-
-                    var spawnedNetworkObject = NetworkObject.AddSceneObject(sceneObject, InternalBuffer, networkManager);
-                    if (!m_NetworkObjectsSync.Contains(spawnedNetworkObject))
-                    {
-                        m_NetworkObjectsSync.Add(spawnedNetworkObject);
-                    }
-                }
-
             // Process all de-spawned in-scene NetworkObjects for this network session
             m_DespawnedInSceneObjects.Clear();
             InternalBuffer.ReadValueSafe(out int despawnedObjectsCount);
@@ -742,8 +781,8 @@ namespace Unity.Netcode
             for (int i = 0; i < despawnedObjectsCount; i++)
             {
                 // We just need to get the scene
-                    ByteUnpacker.ReadValuePacked(InternalBuffer, out int networkSceneHandle);
+                InternalBuffer.ReadValueSafe(out int networkSceneHandle);
-                    ByteUnpacker.ReadValuePacked(InternalBuffer, out uint globalObjectIdHash);
+                InternalBuffer.ReadValueSafe(out uint globalObjectIdHash);
                 var sceneRelativeNetworkObjects = new Dictionary<uint, NetworkObject>();
                 if (!sceneCache.ContainsKey(networkSceneHandle))
                 {
@@ -753,13 +792,24 @@ namespace Unity.Netcode
                         if (m_NetworkManager.SceneManager.ScenesLoaded.ContainsKey(localSceneHandle))
                         {
                             var objectRelativeScene = m_NetworkManager.SceneManager.ScenesLoaded[localSceneHandle];
-                                var inSceneNetworkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>().Where((c) =>
+
+                            // Find all active and non-active in-scene placed NetworkObjects
+#if UNITY_2023_1_OR_NEWER
+                            var inSceneNetworkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(UnityEngine.FindObjectsInactive.Include, UnityEngine.FindObjectsSortMode.InstanceID).Where((c) =>
                             c.GetSceneOriginHandle() == localSceneHandle && (c.IsSceneObject != false)).ToList();
+#else
+                            var inSceneNetworkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>(includeInactive: true).Where((c) =>
+                            c.GetSceneOriginHandle() == localSceneHandle && (c.IsSceneObject != false)).ToList();
+#endif
+
 
                             foreach (var inSceneObject in inSceneNetworkObjects)
+                            {
+                                if (!sceneRelativeNetworkObjects.ContainsKey(inSceneObject.GlobalObjectIdHash))
                                 {
                                     sceneRelativeNetworkObjects.Add(inSceneObject.GlobalObjectIdHash, inSceneObject);
                                 }
+                            }
                             // Add this to a cache so we don't have to run this potentially multiple times (nothing will spawn or despawn during this time
                             sceneCache.Add(networkSceneHandle, sceneRelativeNetworkObjects);
                         }
@@ -793,7 +843,6 @@ namespace Unity.Netcode
                     {
                         m_NetworkManager.SceneManager.ScenePlacedObjects[globalObjectIdHash].Add(sceneRelativeNetworkObjects[globalObjectIdHash].GetSceneOriginHandle(), sceneRelativeNetworkObjects[globalObjectIdHash]);
                     }
-
                 }
                 else
                 {
@@ -801,6 +850,46 @@ namespace Unity.Netcode
                 }
             }
         }
+
+        /// <summary>
+        /// Client Side:
+        /// During the processing of a server sent Event_Sync, this method will be called for each scene once
+        /// it is finished loading.  The client will also build a list of NetworkObjects that it spawned during
+        /// this process which will be used as part of the Event_Sync_Complete response.
+        /// </summary>
+        /// <param name="networkManager"></param>
+        internal void SynchronizeSceneNetworkObjects(NetworkManager networkManager)
+        {
+            try
+            {
+                // Process all spawned NetworkObjects for this network session
+                InternalBuffer.ReadValueSafe(out int newObjectsCount);
+                for (int i = 0; i < newObjectsCount; i++)
+                {
+                    var sceneObject = new NetworkObject.SceneObject();
+                    sceneObject.Deserialize(InternalBuffer);
+
+                    // If the sceneObject is in-scene placed, then set the scene being synchronized
+                    if (sceneObject.IsSceneObject)
+                    {
+                        m_NetworkManager.SceneManager.SetTheSceneBeingSynchronized(sceneObject.NetworkSceneHandle);
+                    }
+                    var spawnedNetworkObject = NetworkObject.AddSceneObject(sceneObject, InternalBuffer, networkManager);
+
+                    // If we failed to deserialize the NetowrkObject then don't add null to the list
+                    if (spawnedNetworkObject != null)
+                    {
+                        if (!m_NetworkObjectsSync.Contains(spawnedNetworkObject))
+                        {
+                            m_NetworkObjectsSync.Add(spawnedNetworkObject);
+                        }
+                    }
+                }
+
+                // Now deserialize the despawned in-scene placed NetworkObjects list (if any)
+                DeserializeDespawnedInScenePlacedNetworkObjects();
+
+            }
             finally
             {
                 InternalBuffer.Dispose();

Runtime/SceneManagement/SceneEventProgress.cs

@@ -58,12 +58,13 @@ namespace Unity.Netcode
         /// <summary>
         /// List of clientIds of those clients that is done loading the scene.
         /// </summary>
-        internal List<ulong> DoneClients { get; } = new List<ulong>();
+        internal Dictionary<ulong, bool> ClientsProcessingSceneEvent { get; } = new Dictionary<ulong, bool>();
+        internal List<ulong> ClientsThatDisconnected = new List<ulong>();
 
         /// <summary>
-        /// The local time when the scene event was "roughly started"
+        /// This is when the current scene event will have timed out
         /// </summary>
-        internal float TimeAtInitiation { get; }
+        internal float WhenSceneEventHasTimedOut;
 
         /// <summary>
         /// Delegate type for when the switch scene progress is completed. Either by all clients done loading the scene or by time out.
@@ -75,17 +76,15 @@ namespace Unity.Netcode
         /// </summary>
         internal OnCompletedDelegate OnComplete;
 
-        /// <summary>
+        internal Action<uint> OnSceneEventCompleted;
-        /// Is this scene switch progresses completed, all clients are done loading the scene or a timeout has occurred.
-        /// </summary>
-        internal bool IsCompleted { get; private set; }
-
-        internal bool TimedOut { get; private set; }
 
         /// <summary>
-        /// If all clients are done loading the scene, at the moment of completed.
+        /// This will make sure that we only have timed out if we never completed
         /// </summary>
-        internal bool AreAllClientsDoneLoading { get; private set; }
+        internal bool HasTimedOut()
+        {
+            return WhenSceneEventHasTimedOut <= Time.realtimeSinceStartup;
+        }
 
         /// <summary>
         /// The hash value generated from the full scene path
@@ -93,9 +92,10 @@ namespace Unity.Netcode
         internal uint SceneHash { get; set; }
 
         internal Guid Guid { get; } = Guid.NewGuid();
+        internal uint SceneEventId;
 
         private Coroutine m_TimeOutCoroutine;
-        private AsyncOperation m_SceneLoadOperation;
+        private AsyncOperation m_AsyncOperation;
 
         private NetworkManager m_NetworkManager { get; }
 
@@ -105,21 +105,85 @@ namespace Unity.Netcode
 
         internal LoadSceneMode LoadSceneMode;
 
-        internal List<ulong> ClientsThatStartedSceneEvent;
+        internal List<ulong> GetClientsWithStatus(bool completedSceneEvent)
+        {
+            var clients = new List<ulong>();
+            if (completedSceneEvent)
+            {
+                // If we are the host, then add the host-client to the list
+                // of clients that completed if the AsyncOperation is done.
+                if (m_NetworkManager.IsHost && m_AsyncOperation.isDone)
+                {
+                    clients.Add(m_NetworkManager.LocalClientId);
+                }
+
+                // Add all clients that completed the scene event
+                foreach (var clientStatus in ClientsProcessingSceneEvent)
+                {
+                    if (clientStatus.Value == completedSceneEvent)
+                    {
+                        clients.Add(clientStatus.Key);
+                    }
+                }
+            }
+            else
+            {
+                // If we are the host, then add the host-client to the list
+                // of clients that did not complete if the AsyncOperation is
+                // not done.
+                if (m_NetworkManager.IsHost && !m_AsyncOperation.isDone)
+                {
+                    clients.Add(m_NetworkManager.LocalClientId);
+                }
+
+                // If we are getting the list of clients that have not completed the
+                // scene event, then add any clients that disconnected during this
+                // scene event.
+                clients.AddRange(ClientsThatDisconnected);
+            }
+            return clients;
+        }
 
         internal SceneEventProgress(NetworkManager networkManager, SceneEventProgressStatus status = SceneEventProgressStatus.Started)
         {
             if (status == SceneEventProgressStatus.Started)
             {
-                // Track the clients that were connected when we started this event
-                ClientsThatStartedSceneEvent = new List<ulong>(networkManager.ConnectedClientsIds);
                 m_NetworkManager = networkManager;
+
+                if (networkManager.IsServer)
+                {
+                    m_NetworkManager.OnClientDisconnectCallback += OnClientDisconnectCallback;
+                    // Track the clients that were connected when we started this event
+                    foreach (var connectedClientId in networkManager.ConnectedClientsIds)
+                    {
+                        // Ignore the host client
+                        if (NetworkManager.ServerClientId == connectedClientId)
+                        {
+                            continue;
+                        }
+                        ClientsProcessingSceneEvent.Add(connectedClientId, false);
+                    }
+
+                    WhenSceneEventHasTimedOut = Time.realtimeSinceStartup + networkManager.NetworkConfig.LoadSceneTimeOut;
                     m_TimeOutCoroutine = m_NetworkManager.StartCoroutine(TimeOutSceneEventProgress());
-                TimeAtInitiation = Time.realtimeSinceStartup;
+                }
             }
             Status = status;
         }
 
+        /// <summary>
+        /// Remove the client from the clients processing the current scene event
+        /// Add this client to the clients that disconnected list
+        /// </summary>
+        private void OnClientDisconnectCallback(ulong clientId)
+        {
+            if (ClientsProcessingSceneEvent.ContainsKey(clientId))
+            {
+                ClientsThatDisconnected.Add(clientId);
+                ClientsProcessingSceneEvent.Remove(clientId);
+            }
+        }
+
         /// <summary>
         /// Coroutine that checks to see if the scene event is complete every network tick period.
         /// This will handle completing the scene event when one or more client(s) disconnect(s)
@@ -129,79 +193,107 @@ namespace Unity.Netcode
         internal IEnumerator TimeOutSceneEventProgress()
         {
             var waitForNetworkTick = new WaitForSeconds(1.0f / m_NetworkManager.NetworkConfig.TickRate);
-            while (!TimedOut && !IsCompleted)
+            while (!HasTimedOut())
             {
                 yield return waitForNetworkTick;
 
-                CheckCompletion();
+                TryFinishingSceneEventProgress();
-                if (!IsCompleted)
-                {
-                    TimedOut = TimeAtInitiation - Time.realtimeSinceStartup >= m_NetworkManager.NetworkConfig.LoadSceneTimeOut;
             }
         }
-        }
-
-        internal void AddClientAsDone(ulong clientId)
-        {
-            DoneClients.Add(clientId);
-            CheckCompletion();
-        }
-
-        internal void RemoveClientAsDone(ulong clientId)
-        {
-            DoneClients.Remove(clientId);
-            CheckCompletion();
-        }
-
-        internal void SetSceneLoadOperation(AsyncOperation sceneLoadOperation)
-        {
-            m_SceneLoadOperation = sceneLoadOperation;
-            m_SceneLoadOperation.completed += operation => CheckCompletion();
-        }
 
         /// <summary>
-        /// Called only on the server-side during integration test (NetcodeIntegrationTest specific)
+        /// Sets the client's scene event progress to finished/true
-        /// scene loading and unloading.
-        ///
-        /// Note: During integration testing we must queue all scene loading and unloading requests for
-        /// both the server and all clients so they can be processed in a FIFO/linear fashion to avoid
-        /// conflicts when the  <see cref="SceneManager.sceneLoaded"/> and <see cref="SceneManager.sceneUnloaded"/>
-        /// events are triggered. The Completed action simulates the <see cref="AsyncOperation.completed"/> event.
-        /// (See: Unity.Netcode.TestHelpers.Runtime.IntegrationTestSceneHandler)
         /// </summary>
-        internal void SetSceneLoadOperation(ISceneManagerHandler.SceneEventAction sceneEventAction)
+        internal void ClientFinishedSceneEvent(ulong clientId)
         {
-            sceneEventAction.Completed = SetComplete;
+            if (ClientsProcessingSceneEvent.ContainsKey(clientId))
+            {
+                ClientsProcessingSceneEvent[clientId] = true;
+                TryFinishingSceneEventProgress();
+            }
         }
 
         /// <summary>
-        /// Finalizes the SceneEventProgress
+        /// Determines if the scene event has finished for both
+        /// client(s) and server.
         /// </summary>
-        internal void SetComplete()
+        /// <remarks>
+        /// The server checks if all known clients processing this scene event
+        /// have finished and then it returns its local AsyncOperation status.
+        /// Clients finish when their AsyncOperation finishes.
+        /// </remarks>
+        private bool HasFinished()
         {
-            IsCompleted = true;
+            // If the network session is terminated/terminating then finish tracking
-            AreAllClientsDoneLoading = true;
+            // this scene event
+            if (!IsNetworkSessionActive())
+            {
+                return true;
+            }
 
-            // If OnComplete is not registered or it is and returns true then remove this from the progress tracking
+            // Clients skip over this
-            if (OnComplete == null || (OnComplete != null && OnComplete.Invoke(this)))
+            foreach (var clientStatus in ClientsProcessingSceneEvent)
             {
+                if (!clientStatus.Value)
+                {
+                    return false;
+                }
+            }
+
+            // Return the local scene event's AsyncOperation status
+            // Note: Integration tests process scene loading through a queue
+            // and the AsyncOperation could not be assigned for several
+            // network tick periods. Return false if that is the case.
+            return m_AsyncOperation == null ? false : m_AsyncOperation.isDone;
+        }
+
+        /// <summary>
+        /// Sets the AsyncOperation for the scene load/unload event
+        /// </summary>
+        internal void SetAsyncOperation(AsyncOperation asyncOperation)
+        {
+            m_AsyncOperation = asyncOperation;
+            m_AsyncOperation.completed += new Action<AsyncOperation>(asyncOp2 =>
+            {
+                // Don't invoke the callback if the network session is disconnected
+                // during a SceneEventProgress
+                if (IsNetworkSessionActive())
+                {
+                    OnSceneEventCompleted?.Invoke(SceneEventId);
+                }
+
+                // Go ahead and try finishing even if the network session is terminated/terminating
+                // as we might need to stop the coroutine
+                TryFinishingSceneEventProgress();
+            });
+        }
+
+
+        internal bool IsNetworkSessionActive()
+        {
+            return m_NetworkManager != null && m_NetworkManager.IsListening && !m_NetworkManager.ShutdownInProgress;
+        }
+
+        /// <summary>
+        /// Will try to finish the current scene event in progress as long as
+        /// all conditions are met.
+        /// </summary>
+        internal void TryFinishingSceneEventProgress()
+        {
+            if (HasFinished() || HasTimedOut())
+            {
+                // Don't attempt to finalize this scene event if we are no longer listening or a shutdown is in progress
+                if (IsNetworkSessionActive())
+                {
+                    OnComplete?.Invoke(this);
                     m_NetworkManager.SceneManager.SceneEventProgressTracking.Remove(Guid);
+                    m_NetworkManager.OnClientDisconnectCallback -= OnClientDisconnectCallback;
                 }
+
+                if (m_TimeOutCoroutine != null)
+                {
                     m_NetworkManager.StopCoroutine(m_TimeOutCoroutine);
                 }
-
-        internal void CheckCompletion()
-        {
-            try
-            {
-                if ((!IsCompleted && DoneClients.Count == m_NetworkManager.ConnectedClientsList.Count && (m_SceneLoadOperation == null || m_SceneLoadOperation.isDone)) || (!IsCompleted && TimedOut))
-                {
-                    SetComplete();
-                }
-            }
-            catch (Exception ex)
-            {
-                Debug.LogException(ex);
             }
         }
     }

Runtime/Serialization/BitCounter.cs

@@ -2,6 +2,9 @@ using System.Runtime.CompilerServices;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Utility class to count the number of bytes or bits needed to serialize a value.
+    /// </summary>
     public static class BitCounter
     {
         // Since we don't have access to BitOperations.LeadingZeroCount() (which would have been the fastest)

Runtime/Serialization/BitReader.cs

@@ -21,6 +21,8 @@ namespace Unity.Netcode
 
         private const int k_BitsPerByte = 8;
 
+        private int BytePosition => m_BitPosition >> 3;
+
         /// <summary>
         /// Whether or not the current BitPosition is evenly divisible by 8. I.e. whether or not the BitPosition is at a byte boundary.
         /// </summary>
@@ -98,11 +100,6 @@ namespace Unity.Netcode
                 throw new ArgumentOutOfRangeException(nameof(bitCount), "Cannot read more than 64 bits from a 64-bit value!");
             }
 
-            if (bitCount < 0)
-            {
-                throw new ArgumentOutOfRangeException(nameof(bitCount), "Cannot read fewer than 0 bits!");
-            }
-
             int checkPos = (int)(m_BitPosition + bitCount);
             if (checkPos > m_AllowedBitwiseReadMark)
             {
@@ -165,7 +162,7 @@ namespace Unity.Netcode
 #endif
 
             int offset = m_BitPosition & 7;
-            int pos = m_BitPosition >> 3;
+            int pos = BytePosition;
             bit = (m_BufferPointer[pos] & (1 << offset)) != 0;
             ++m_BitPosition;
         }
@@ -175,7 +172,7 @@ namespace Unity.Netcode
         {
             var val = new T();
             byte* ptr = ((byte*)&val) + offsetBytes;
-            byte* bufferPointer = m_BufferPointer + m_Position;
+            byte* bufferPointer = m_BufferPointer + BytePosition;
             UnsafeUtility.MemCpy(ptr, bufferPointer, bytesToRead);
 
             m_BitPosition += bytesToRead * k_BitsPerByte;

Runtime/Serialization/BitWriter.cs

@@ -29,6 +29,8 @@ namespace Unity.Netcode
             get => (m_BitPosition & 7) == 0;
         }
 
+        private int BytePosition => m_BitPosition >> 3;
+
         internal unsafe BitWriter(FastBufferWriter writer)
         {
             m_Writer = writer;
@@ -181,7 +183,7 @@ namespace Unity.Netcode
 #endif
 
             int offset = m_BitPosition & 7;
-            int pos = m_BitPosition >> 3;
+            int pos = BytePosition;
             ++m_BitPosition;
             m_BufferPointer[pos] = (byte)(bit ? (m_BufferPointer[pos] & ~(1 << offset)) | (1 << offset) : (m_BufferPointer[pos] & ~(1 << offset)));
         }
@@ -190,7 +192,7 @@ namespace Unity.Netcode
         private unsafe void WritePartialValue<T>(T value, int bytesToWrite, int offsetBytes = 0) where T : unmanaged
         {
             byte* ptr = ((byte*)&value) + offsetBytes;
-            byte* bufferPointer = m_BufferPointer + m_Position;
+            byte* bufferPointer = m_BufferPointer + BytePosition;
             UnsafeUtility.MemCpy(bufferPointer, ptr, bytesToWrite);
 
             m_BitPosition += bytesToWrite * k_BitsPerByte;

Runtime/Serialization/BufferSerializer.cs

@@ -62,80 +62,507 @@ namespace Unity.Netcode
             return m_Implementation.GetFastBufferWriter();
         }
 
+
+        /// <summary>
+        /// Read or write a string
+        /// </summary>
+        /// <param name="s">The value to read/write</param>
+        /// <param name="oneByteChars">If true, characters will be limited to one-byte ASCII characters</param>
         public void SerializeValue(ref string s, bool oneByteChars = false) => m_Implementation.SerializeValue(ref s, oneByteChars);
+
+        /// <summary>
+        /// Read or write a single byte
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref byte value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of primitive values (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an enum value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of enum values
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a struct value implementing ISerializeByMemcpy
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of struct values implementing ISerializeByMemcpy
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a struct or class value implementing INetworkSerializable
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of struct or class values implementing INetworkSerializable
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Vector2 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Vector2 value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Vector2 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Vector2[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Vector3 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Vector3 value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Vector3 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Vector3[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Vector2Int value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Vector2Int value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Vector2Int values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Vector2Int[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Vector3Int value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Vector3Int value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Vector3Int values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Vector3Int[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Vector4 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Vector4 value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Vector4 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Vector4[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Quaternion value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Quaternion value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Quaternion values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Quaternion[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Color value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Color value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Color values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Color[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Color32 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Color32 value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Color32 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Color32[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Ray value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Ray value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Ray values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Ray[] value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write a Ray2D value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValue(ref Ray2D value) => m_Implementation.SerializeValue(ref value);
+
+        /// <summary>
+        /// Read or write an array of Ray2D values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValue(ref Ray2D[] value) => m_Implementation.SerializeValue(ref value);
 
         // There are many FixedString types, but all of them share the interfaces INativeList<bool> and IUTF8Bytes.
         // INativeList<bool> provides the Length property
         // IUTF8Bytes provides GetUnsafePtr()
         // Those two are necessary to serialize FixedStrings efficiently
-        // - otherwise we'd just be memcpying the whole thing even if
+        // - otherwise we'd just be memcpy'ing the whole thing even if
         // most of it isn't used.
+        /// <summary>
+        /// Read or write a FixedString value
+        /// </summary>
+        /// <typeparam name="T">The network serializable type</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution of FixedStrings</param>
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes => m_Implementation.SerializeValue(ref value);
 
+        /// <summary>
+        /// Read or write a NetworkSerializable value.
+        /// SerializeValue() is the preferred method to do this - this is provided for backward compatibility only.
+        /// </summary>
+        /// <typeparam name="T">The network serializable type</typeparam>
+        /// <param name="value">The values to read/write</param>
         public void SerializeNetworkSerializable<T>(ref T value) where T : INetworkSerializable, new() => m_Implementation.SerializeNetworkSerializable(ref value);
 
+        /// <summary>
+        /// Performs an advance check to ensure space is available to read/write one or more values.
+        /// This provides a performance benefit for serializing multiple values using the
+        /// SerializeValuePreChecked methods. But note that the benefit is small and only likely to be
+        /// noticeable if serializing a very large number of items.
+        /// </summary>
+        /// <param name="amount"></param>
+        /// <returns></returns>
         public bool PreCheck(int amount)
         {
             return m_Implementation.PreCheck(amount);
         }
 
+        /// <summary>
+        /// Serialize a string, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="s">The value to read/write</param>
+        /// <param name="oneByteChars">If true, characters will be limited to one-byte ASCII characters</param>
         public void SerializeValuePreChecked(ref string s, bool oneByteChars = false) => m_Implementation.SerializeValuePreChecked(ref s, oneByteChars);
+
+        /// <summary>
+        /// Serialize a byte, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref byte value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a primitive, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable type</typeparam>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         public void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize an array of primitives, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable types in an array</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution of primitives</param>
         public void SerializeValuePreChecked<T>(ref T[] value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize an enum, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable type</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution of enums</param>
         public void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize an array of enums, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable types in an array</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution of enums</param>
         public void SerializeValuePreChecked<T>(ref T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a struct, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable type</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution of structs</param>
         public void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize an array of structs, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable types in an array</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution of structs</param>
         public void SerializeValuePreChecked<T>(ref T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector2, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector2 value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector2 array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValuePreChecked(ref Vector2[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector3, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector3 value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector3 array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValuePreChecked(ref Vector3[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector2Int, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector2Int value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector2Int array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         public void SerializeValuePreChecked(ref Vector2Int[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector3Int, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector3Int value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector3Int array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector3Int[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector4, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector4 value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Vector4Array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Vector4[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Quaternion, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Quaternion value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Quaternion array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Quaternion[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Color, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Color value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Color array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Color[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Color32, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Color32 value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Color32 array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Color32[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Ray, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Ray value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Ray array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Ray[] value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Ray2D, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Ray2D value) => m_Implementation.SerializeValuePreChecked(ref value);
+
+        /// <summary>
+        /// Serialize a Ray2D array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         public void SerializeValuePreChecked(ref Ray2D[] value) => m_Implementation.SerializeValuePreChecked(ref value);
 
         // There are many FixedString types, but all of them share the interfaces INativeList<bool> and IUTF8Bytes.
@@ -144,6 +571,16 @@ namespace Unity.Netcode
         // Those two are necessary to serialize FixedStrings efficiently
         // - otherwise we'd just be memcpying the whole thing even if
         // most of it isn't used.
+
+        /// <summary>
+        /// Serialize a FixedString, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The network serializable type</typeparam>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution for fixed strings</param>
         public void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes => m_Implementation.SerializeValuePreChecked(ref value);
     }

Runtime/Serialization/BufferSerializerReader.cs

@@ -34,7 +34,7 @@ namespace Unity.Netcode
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => m_Reader.ReadValueSafe(out value);
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => m_Reader.ReadValueSafe(out value);
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => m_Reader.ReadValueSafe(out value);
-        public void SerializeValue<T>(ref T value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => m_Reader.ReadValue(out value);
+        public void SerializeValue<T>(ref T value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => m_Reader.ReadNetworkSerializableInPlace(ref value);
         public void SerializeValue<T>(ref T[] value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => m_Reader.ReadValue(out value);
 
         public void SerializeValue<T>(ref T value, FastBufferWriter.ForFixedStrings unused = default)

Runtime/Serialization/BytePacker.cs

@@ -6,6 +6,7 @@ namespace Unity.Netcode
 {
     /// <summary>
     /// Utility class for packing values in serialization.
+    /// <seealso cref="ByteUnpacker"/> to unpack packed values.
     /// </summary>
     public static class BytePacker
     {
@@ -49,7 +50,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void WriteValuePacked(FastBufferWriter writer, float value)
         {
-            WriteUInt32Packed(writer, ToUint(value));
+            WriteValueBitPacked(writer, ToUint(value));
         }
 
         /// <summary>
@@ -60,7 +61,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void WriteValuePacked(FastBufferWriter writer, double value)
         {
-            WriteUInt64Packed(writer, ToUlong(value));
+            WriteValueBitPacked(writer, ToUlong(value));
         }
 
         /// <summary>
@@ -97,7 +98,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, short value) => WriteUInt32Packed(writer, (ushort)Arithmetic.ZigZagEncode(value));
+        public static void WriteValuePacked(FastBufferWriter writer, short value) => WriteValueBitPacked(writer, value);
 
         /// <summary>
         /// Write an unsigned short (UInt16) as a varint to the buffer.
@@ -108,7 +109,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, ushort value) => WriteUInt32Packed(writer, value);
+        public static void WriteValuePacked(FastBufferWriter writer, ushort value) => WriteValueBitPacked(writer, value);
 
         /// <summary>
         /// Write a two-byte character as a varint to the buffer.
@@ -119,7 +120,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="c">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, char c) => WriteUInt32Packed(writer, c);
+        public static void WriteValuePacked(FastBufferWriter writer, char c) => WriteValueBitPacked(writer, c);
 
         /// <summary>
         /// Write a signed int (Int32) as a ZigZag encoded varint to the buffer.
@@ -127,7 +128,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, int value) => WriteUInt32Packed(writer, (uint)Arithmetic.ZigZagEncode(value));
+        public static void WriteValuePacked(FastBufferWriter writer, int value) => WriteValueBitPacked(writer, value);
 
         /// <summary>
         /// Write an unsigned int (UInt32) to the buffer.
@@ -135,7 +136,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, uint value) => WriteUInt32Packed(writer, value);
+        public static void WriteValuePacked(FastBufferWriter writer, uint value) => WriteValueBitPacked(writer, value);
 
         /// <summary>
         /// Write an unsigned long (UInt64) to the buffer.
@@ -143,7 +144,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, ulong value) => WriteUInt64Packed(writer, value);
+        public static void WriteValuePacked(FastBufferWriter writer, ulong value) => WriteValueBitPacked(writer, value);
 
         /// <summary>
         /// Write a signed long (Int64) as a ZigZag encoded varint to the buffer.
@@ -151,7 +152,7 @@ namespace Unity.Netcode
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">Value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void WriteValuePacked(FastBufferWriter writer, long value) => WriteUInt64Packed(writer, Arithmetic.ZigZagEncode(value));
+        public static void WriteValuePacked(FastBufferWriter writer, long value) => WriteValueBitPacked(writer, value);
 
         /// <summary>
         /// Convenience method that writes two packed Vector3 from the ray to the buffer
@@ -281,196 +282,183 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueBitPacked<T>(FastBufferWriter writer, T value) where T: unmanaged => writer.WriteValueSafe(value);
 #else
-
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const ushort BitPackedUshortMax = (1 << 15) - 1;
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const short BitPackedShortMax = (1 << 14) - 1;
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const short BitPackedShortMin = -(1 << 14);
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const uint BitPackedUintMax = (1 << 30) - 1;
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const int BitPackedIntMax = (1 << 29) - 1;
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const int BitPackedIntMin = -(1 << 29);
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const ulong BitPackedULongMax = (1L << 61) - 1;
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const long BitPackedLongMax = (1L << 60) - 1;
+
+        /// <summary>
+        /// Obsolete value that no longer carries meaning. Do not use.
+        /// </summary>
         public const long BitPackedLongMin = -(1L << 60);
 
         /// <summary>
-        /// Writes a 14-bit signed short to the buffer in a bit-encoded packed format.
+        /// Writes a 16-bit signed short to the buffer in a bit-encoded packed format.
-        /// The first bit indicates whether the value is 1 byte or 2.
+        /// Zig-zag encoding is used to move the sign bit to the least significant bit, so that negative values
-        /// The sign bit takes up another bit.
+        /// are still able to be compressed.
-        /// That leaves 14 bits for the value.
+        /// The first two bits indicate whether the value is 1, 2, or 3 bytes.
-        /// A value greater than 2^14-1 or less than -2^14 will throw an exception in editor and development builds.
+        /// If the value uses 14 bits or less, the remaining 14 bits contain the value.
-        /// In release builds builds the exception is not thrown and the value is truncated by losing its two
+        /// For performance, reasons, if the value is 15 bits or more, there will be six 0 bits, followed
-        /// most significant bits after zig-zag encoding.
+        /// by the original unmodified 16-bit value in the next 2 bytes.
         /// </summary>
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">The value to pack</param>
         public static void WriteValueBitPacked(FastBufferWriter writer, short value) => WriteValueBitPacked(writer, (ushort)Arithmetic.ZigZagEncode(value));
 
         /// <summary>
-        /// Writes a 15-bit unsigned short to the buffer in a bit-encoded packed format.
+        /// Writes a 16-bit unsigned short to the buffer in a bit-encoded packed format.
-        /// The first bit indicates whether the value is 1 byte or 2.
+        /// The first two bits indicate whether the value is 1, 2, or 3 bytes.
-        /// That leaves 15 bits for the value.
+        /// If the value uses 14 bits or less, the remaining 14 bits contain the value.
-        /// A value greater than 2^15-1 will throw an exception in editor and development builds.
+        /// For performance, reasons, if the value is 15 bits or more, there will be six 0 bits, followed
-        /// In release builds builds the exception is not thrown and the value is truncated by losing its
+        /// by the original unmodified 16-bit value in the next 2 bytes.
-        /// most significant bit.
         /// </summary>
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">The value to pack</param>
         public static void WriteValueBitPacked(FastBufferWriter writer, ushort value)
         {
-#if DEVELOPMENT_BUILD || UNITY_EDITOR
+            if (value > (1 << 14) - 1)
-            if (value >= BitPackedUshortMax)
             {
-                throw new ArgumentException("BitPacked ushorts must be <= 15 bits");
+                if (!writer.TryBeginWriteInternal(3))
-            }
-#endif
-
-            if (value <= 0b0111_1111)
-            {
-                if (!writer.TryBeginWriteInternal(1))
                 {
                     throw new OverflowException("Writing past the end of the buffer");
                 }
-                writer.WriteByte((byte)(value << 1));
+                writer.WriteByte(3);
+                writer.WriteValue(value);
                 return;
             }
 
-            if (!writer.TryBeginWriteInternal(2))
-            {
-                throw new OverflowException("Writing past the end of the buffer");
-            }
-            writer.WriteValue((ushort)((value << 1) | 0b1));
-        }
-
-        /// <summary>
-        /// Writes a 29-bit signed int to the buffer in a bit-encoded packed format.
-        /// The first two bits indicate whether the value is 1, 2, 3, or 4 bytes.
-        /// The sign bit takes up another bit.
-        /// That leaves 29 bits for the value.
-        /// A value greater than 2^29-1 or less than -2^29 will throw an exception in editor and development builds.
-        /// In release builds builds the exception is not thrown and the value is truncated by losing its three
-        /// most significant bits after zig-zag encoding.
-        /// </summary>
-        /// <param name="writer">The writer to write to</param>
-        /// <param name="value">The value to pack</param>
-        public static void WriteValueBitPacked(FastBufferWriter writer, int value) => WriteValueBitPacked(writer, (uint)Arithmetic.ZigZagEncode(value));
-
-        /// <summary>
-        /// Writes a 30-bit unsigned int to the buffer in a bit-encoded packed format.
-        /// The first two bits indicate whether the value is 1, 2, 3, or 4 bytes.
-        /// That leaves 30 bits for the value.
-        /// A value greater than 2^30-1 will throw an exception in editor and development builds.
-        /// In release builds builds the exception is not thrown and the value is truncated by losing its two
-        /// most significant bits.
-        /// </summary>
-        /// <param name="writer">The writer to write to</param>
-        /// <param name="value">The value to pack</param>
-        public static void WriteValueBitPacked(FastBufferWriter writer, uint value)
-        {
-#if DEVELOPMENT_BUILD || UNITY_EDITOR
-            if (value > BitPackedUintMax)
-            {
-                throw new ArgumentException("BitPacked uints must be <= 30 bits");
-            }
-#endif
             value <<= 2;
             var numBytes = BitCounter.GetUsedByteCount(value);
             if (!writer.TryBeginWriteInternal(numBytes))
             {
                 throw new OverflowException("Writing past the end of the buffer");
             }
-            writer.WritePartialValue(value | (uint)(numBytes - 1), numBytes);
+            writer.WritePartialValue(value | (ushort)(numBytes), numBytes);
         }
 
         /// <summary>
-        /// Writes a 60-bit signed long to the buffer in a bit-encoded packed format.
+        /// Writes a 32-bit signed int to the buffer in a bit-encoded packed format.
-        /// The first three bits indicate whether the value is 1, 2, 3, 4, 5, 6, 7, or 8 bytes.
+        /// Zig-zag encoding is used to move the sign bit to the least significant bit, so that negative values
-        /// The sign bit takes up another bit.
+        /// are still able to be compressed.
-        /// That leaves 60 bits for the value.
+        /// The first three bits indicate whether the value is 1, 2, 3, 4, or 5 bytes.
-        /// A value greater than 2^60-1 or less than -2^60 will throw an exception in editor and development builds.
+        /// If the value uses 29 bits or less, the remaining 29 bits contain the value.
-        /// In release builds builds the exception is not thrown and the value is truncated by losing its four
+        /// For performance, reasons, if the value is 30 bits or more, there will be five 0 bits, followed
-        /// most significant bits after zig-zag encoding.
+        /// by the original unmodified 32-bit value in the next 4 bytes.
         /// </summary>
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">The value to pack</param>
-        public static void WriteValueBitPacked(FastBufferWriter writer, long value) => WriteValueBitPacked(writer, Arithmetic.ZigZagEncode(value));
+        public static void WriteValueBitPacked(FastBufferWriter writer, int value) => WriteValueBitPacked(writer, (uint)Arithmetic.ZigZagEncode(value));
 
         /// <summary>
-        /// Writes a 61-bit unsigned long to the buffer in a bit-encoded packed format.
+        /// Writes a 32-bit unsigned int to the buffer in a bit-encoded packed format.
-        /// The first three bits indicate whether the value is 1, 2, 3, 4, 5, 6, 7, or 8 bytes.
+        /// The first three bits indicate whether the value is 1, 2, 3, 4, or 5 bytes.
-        /// That leaves 31 bits for the value.
+        /// If the value uses 29 bits or less, the remaining 29 bits contain the value.
-        /// A value greater than 2^61-1 will throw an exception in editor and development builds.
+        /// For performance, reasons, if the value is 30 bits or more, there will be five 0 bits, followed
-        /// In release builds builds the exception is not thrown and the value is truncated by losing its three
+        /// by the original unmodified 32-bit value in the next 4 bytes.
-        /// most significant bits.
         /// </summary>
         /// <param name="writer">The writer to write to</param>
         /// <param name="value">The value to pack</param>
-        public static void WriteValueBitPacked(FastBufferWriter writer, ulong value)
+        public static void WriteValueBitPacked(FastBufferWriter writer, uint value)
         {
-#if DEVELOPMENT_BUILD || UNITY_EDITOR
+            if (value > (1 << 29) - 1)
-            if (value > BitPackedULongMax)
             {
-                throw new ArgumentException("BitPacked ulongs must be <= 61 bits");
+                if (!writer.TryBeginWriteInternal(5))
+                {
+                    throw new OverflowException("Writing past the end of the buffer");
                 }
-#endif
+                writer.WriteByte(5);
+                writer.WriteValue(value);
+                return;
+            }
+
             value <<= 3;
             var numBytes = BitCounter.GetUsedByteCount(value);
             if (!writer.TryBeginWriteInternal(numBytes))
             {
                 throw new OverflowException("Writing past the end of the buffer");
             }
-            writer.WritePartialValue(value | (uint)(numBytes - 1), numBytes);
+            writer.WritePartialValue(value | (uint)(numBytes), numBytes);
+        }
+
+        /// <summary>
+        /// Writes a 64-bit signed long to the buffer in a bit-encoded packed format.
+        /// Zig-zag encoding is used to move the sign bit to the least significant bit, so that negative values
+        /// are still able to be compressed.
+        /// The first four bits indicate whether the value is 1, 2, 3, 4, 5, 6, 7, 8, or 9 bytes.
+        /// If the value uses 60 bits or less, the remaining 60 bits contain the value.
+        /// For performance, reasons, if the value is 61 bits or more, there will be four 0 bits, followed
+        /// by the original unmodified 64-bit value in the next 8 bytes.
+        /// </summary>
+        /// <param name="writer">The writer to write to</param>
+        /// <param name="value">The value to pack</param>
+        public static void WriteValueBitPacked(FastBufferWriter writer, long value) => WriteValueBitPacked(writer, Arithmetic.ZigZagEncode(value));
+
+        /// <summary>
+        /// Writes a 64-bit unsigned long to the buffer in a bit-encoded packed format.
+        /// The first four bits indicate whether the value is 1, 2, 3, 4, 5, 6, 7, 8, or 9 bytes.
+        /// If the value uses 60 bits or less, the remaining 60 bits contain the value.
+        /// For performance, reasons, if the value is 61 bits or more, there will be four 0 bits, followed
+        /// by the original unmodified 64-bit value in the next 8 bytes.
+        /// </summary>
+        /// <param name="writer">The writer to write to</param>
+        /// <param name="value">The value to pack</param>
+        public static void WriteValueBitPacked(FastBufferWriter writer, ulong value)
+        {
+            if (value > (1L << 60) - 1)
+            {
+                if (!writer.TryBeginWriteInternal(9))
+                {
+                    throw new OverflowException("Writing past the end of the buffer");
+                }
+                writer.WriteByte(9);
+                writer.WriteValue(value);
+                return;
+            }
+
+            value <<= 4;
+            var numBytes = BitCounter.GetUsedByteCount(value);
+            if (!writer.TryBeginWriteInternal(numBytes))
+            {
+                throw new OverflowException("Writing past the end of the buffer");
+            }
+            writer.WritePartialValue(value | (uint)(numBytes), numBytes);
         }
 #endif
-
-        private static void WriteUInt64Packed(FastBufferWriter writer, ulong value)
-        {
-            if (value <= 240)
-            {
-                writer.WriteByteSafe((byte)value);
-                return;
-            }
-            if (value <= 2287)
-            {
-                writer.WriteByteSafe((byte)(((value - 240) >> 8) + 241));
-                writer.WriteByteSafe((byte)(value - 240));
-                return;
-            }
-            var writeBytes = BitCounter.GetUsedByteCount(value);
-
-            if (!writer.TryBeginWriteInternal(writeBytes + 1))
-            {
-                throw new OverflowException("Writing past the end of the buffer");
-            }
-            writer.WriteByte((byte)(247 + writeBytes));
-            writer.WritePartialValue(value, writeBytes);
-        }
-
-        // Looks like the same code as WriteUInt64Packed?
-        // It's actually different because it will call the more efficient 32-bit version
-        // of BytewiseUtility.GetUsedByteCount().
-        private static void WriteUInt32Packed(FastBufferWriter writer, uint value)
-        {
-            if (value <= 240)
-            {
-                writer.WriteByteSafe((byte)value);
-                return;
-            }
-            if (value <= 2287)
-            {
-                writer.WriteByteSafe((byte)(((value - 240) >> 8) + 241));
-                writer.WriteByteSafe((byte)(value - 240));
-                return;
-            }
-            var writeBytes = BitCounter.GetUsedByteCount(value);
-
-            if (!writer.TryBeginWriteInternal(writeBytes + 1))
-            {
-                throw new OverflowException("Writing past the end of the buffer");
-            }
-            writer.WriteByte((byte)(247 + writeBytes));
-            writer.WritePartialValue(value, writeBytes);
-        }
-
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static unsafe uint ToUint<T>(T value) where T : unmanaged
         {

Runtime/Serialization/ByteUnpacker.cs

@@ -4,14 +4,25 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Byte Unpacking Helper Class
+    /// Use this class to unpack values during deserialization for values that were packed.
+    /// <seealso cref="BytePacker"/> to pack unpacked values
+    /// </summary>
     public static class ByteUnpacker
     {
-
 #if UNITY_NETCODE_DEBUG_NO_PACKING
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValuePacked<T>(FastBufferReader reader, out T value) where T: unmanaged => reader.ReadValueSafe(out value);
 #else
+        /// <summary>
+        /// Read a packed enum value
+        /// </summary>
+        /// <param name="reader">The reader to read from</param>
+        /// <param name="value">The value that's read</param>
+        /// <typeparam name="TEnum">Type of enum to read</typeparam>
+        /// <exception cref="InvalidOperationException">Throws InvalidOperationException if an enum somehow ends up not being the size of a byte, short, int, or long (which should be impossible)</exception>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static unsafe void ReadValuePacked<TEnum>(FastBufferReader reader, out TEnum value) where TEnum : unmanaged, Enum
         {
@@ -46,7 +57,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void ReadValuePacked(FastBufferReader reader, out float value)
         {
-            ReadUInt32Packed(reader, out uint asUInt);
+            ReadValueBitPacked(reader, out uint asUInt);
             value = ToSingle(asUInt);
         }
 
@@ -58,7 +69,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void ReadValuePacked(FastBufferReader reader, out double value)
         {
-            ReadUInt64Packed(reader, out ulong asULong);
+            ReadValueBitPacked(reader, out ulong asULong);
             value = ToDouble(asULong);
         }
 
@@ -97,11 +108,7 @@ namespace Unity.Netcode
         /// <param name="reader">The reader to read from</param>
         /// <param name="value">Value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReadValuePacked(FastBufferReader reader, out short value)
+        public static void ReadValuePacked(FastBufferReader reader, out short value) => ReadValueBitPacked(reader, out value);
-        {
-            ReadUInt32Packed(reader, out uint readValue);
-            value = (short)Arithmetic.ZigZagDecode(readValue);
-        }
 
         /// <summary>
         /// Read an unsigned short (UInt16) as a varint from the stream.
@@ -109,11 +116,7 @@ namespace Unity.Netcode
         /// <param name="reader">The reader to read from</param>
         /// <param name="value">Value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReadValuePacked(FastBufferReader reader, out ushort value)
+        public static void ReadValuePacked(FastBufferReader reader, out ushort value) => ReadValueBitPacked(reader, out value);
-        {
-            ReadUInt32Packed(reader, out uint readValue);
-            value = (ushort)readValue;
-        }
 
         /// <summary>
         /// Read a two-byte character as a varint from the stream.
@@ -123,7 +126,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void ReadValuePacked(FastBufferReader reader, out char c)
         {
-            ReadUInt32Packed(reader, out uint readValue);
+            ReadValueBitPacked(reader, out ushort readValue);
             c = (char)readValue;
         }
 
@@ -133,11 +136,7 @@ namespace Unity.Netcode
         /// <param name="reader">The reader to read from</param>
         /// <param name="value">Value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReadValuePacked(FastBufferReader reader, out int value)
+        public static void ReadValuePacked(FastBufferReader reader, out int value) => ReadValueBitPacked(reader, out value);
-        {
-            ReadUInt32Packed(reader, out uint readValue);
-            value = (int)Arithmetic.ZigZagDecode(readValue);
-        }
 
         /// <summary>
         /// Read an unsigned int (UInt32) from the stream.
@@ -145,7 +144,7 @@ namespace Unity.Netcode
         /// <param name="reader">The reader to read from</param>
         /// <param name="value">Value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReadValuePacked(FastBufferReader reader, out uint value) => ReadUInt32Packed(reader, out value);
+        public static void ReadValuePacked(FastBufferReader reader, out uint value) => ReadValueBitPacked(reader, out value);
 
         /// <summary>
         /// Read an unsigned long (UInt64) from the stream.
@@ -153,7 +152,7 @@ namespace Unity.Netcode
         /// <param name="reader">The reader to read from</param>
         /// <param name="value">Value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReadValuePacked(FastBufferReader reader, out ulong value) => ReadUInt64Packed(reader, out value);
+        public static void ReadValuePacked(FastBufferReader reader, out ulong value) => ReadValueBitPacked(reader, out value);
 
         /// <summary>
         /// Read a signed long (Int64) as a ZigZag encoded varint from the stream.
@@ -163,8 +162,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void ReadValuePacked(FastBufferReader reader, out long value)
         {
-            ReadUInt64Packed(reader, out ulong readValue);
+            ReadValueBitPacked(reader, out value);
-            value = Arithmetic.ZigZagDecode(readValue);
         }
 
         /// <summary>
@@ -329,7 +327,9 @@ namespace Unity.Netcode
             ushort returnValue = 0;
             byte* ptr = ((byte*)&returnValue);
             byte* data = reader.GetUnsafePtrAtCurrentPosition();
-            int numBytes = (data[0] & 0b1) + 1;
+            // Mask out the first two bits - they contain the total byte count
+            // (1, 2, or 3)
+            int numBytes = (data[0] & 0b11);
             if (!reader.TryBeginReadInternal(numBytes))
             {
                 throw new OverflowException("Reading past the end of the buffer");
@@ -338,17 +338,23 @@ namespace Unity.Netcode
             switch (numBytes)
             {
                 case 1:
-                    *ptr = *data;
+                    ptr[0] = data[0];
                     break;
                 case 2:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
                     break;
+                case 3:
+                    // First byte contains no data, it's just a marker. The data is in the remaining two bytes.
+                    ptr[0] = data[1];
+                    ptr[1] = data[2];
+                    value = returnValue;
+                    return;
                 default:
                     throw new InvalidOperationException("Could not read bit-packed value: impossible byte count");
             }
 
-            value = (ushort)(returnValue >> 1);
+            value = (ushort)(returnValue >> 2);
         }
 
         /// <summary>
@@ -374,7 +380,8 @@ namespace Unity.Netcode
             uint returnValue = 0;
             byte* ptr = ((byte*)&returnValue);
             byte* data = reader.GetUnsafePtrAtCurrentPosition();
-            int numBytes = (data[0] & 0b11) + 1;
+            // Mask out the first three bits - they contain the total byte count (1-5)
+            int numBytes = (data[0] & 0b111);
             if (!reader.TryBeginReadInternal(numBytes))
             {
                 throw new OverflowException("Reading past the end of the buffer");
@@ -383,26 +390,34 @@ namespace Unity.Netcode
             switch (numBytes)
             {
                 case 1:
-                    *ptr = *data;
+                    ptr[0] = data[0];
                     break;
                 case 2:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
                     break;
                 case 3:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
                     break;
                 case 4:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
-                    *(ptr + 3) = *(data + 3);
+                    ptr[3] = data[3];
                     break;
+                case 5:
+                    // First byte contains no data, it's just a marker. The data is in the remaining two bytes.
+                    ptr[0] = data[1];
+                    ptr[1] = data[2];
+                    ptr[2] = data[3];
+                    ptr[3] = data[4];
+                    value = returnValue;
+                    return;
             }
 
-            value = returnValue >> 2;
+            value = returnValue >> 3;
         }
 
         /// <summary>
@@ -428,7 +443,8 @@ namespace Unity.Netcode
             ulong returnValue = 0;
             byte* ptr = ((byte*)&returnValue);
             byte* data = reader.GetUnsafePtrAtCurrentPosition();
-            int numBytes = (data[0] & 0b111) + 1;
+            // Mask out the first four bits - they contain the total byte count (1-9)
+            int numBytes = (data[0] & 0b1111);
             if (!reader.TryBeginReadInternal(numBytes))
             {
                 throw new OverflowException("Reading past the end of the buffer");
@@ -437,109 +453,74 @@ namespace Unity.Netcode
             switch (numBytes)
             {
                 case 1:
-                    *ptr = *data;
+                    ptr[0] = data[0];
                     break;
                 case 2:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
                     break;
                 case 3:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
                     break;
                 case 4:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
-                    *(ptr + 3) = *(data + 3);
+                    ptr[3] = data[3];
                     break;
                 case 5:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
-                    *(ptr + 3) = *(data + 3);
+                    ptr[3] = data[3];
-                    *(ptr + 4) = *(data + 4);
+                    ptr[4] = data[4];
                     break;
                 case 6:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
-                    *(ptr + 3) = *(data + 3);
+                    ptr[3] = data[3];
-                    *(ptr + 4) = *(data + 4);
+                    ptr[4] = data[4];
-                    *(ptr + 5) = *(data + 5);
+                    ptr[5] = data[5];
                     break;
                 case 7:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
-                    *(ptr + 3) = *(data + 3);
+                    ptr[3] = data[3];
-                    *(ptr + 4) = *(data + 4);
+                    ptr[4] = data[4];
-                    *(ptr + 5) = *(data + 5);
+                    ptr[5] = data[5];
-                    *(ptr + 6) = *(data + 6);
+                    ptr[6] = data[6];
                     break;
                 case 8:
-                    *ptr = *data;
+                    ptr[0] = data[0];
-                    *(ptr + 1) = *(data + 1);
+                    ptr[1] = data[1];
-                    *(ptr + 2) = *(data + 2);
+                    ptr[2] = data[2];
-                    *(ptr + 3) = *(data + 3);
+                    ptr[3] = data[3];
-                    *(ptr + 4) = *(data + 4);
+                    ptr[4] = data[4];
-                    *(ptr + 5) = *(data + 5);
+                    ptr[5] = data[5];
-                    *(ptr + 6) = *(data + 6);
+                    ptr[6] = data[6];
-                    *(ptr + 7) = *(data + 7);
+                    ptr[7] = data[7];
                     break;
+                case 9:
+                    // First byte contains no data, it's just a marker. The data is in the remaining two bytes.
+                    ptr[0] = data[1];
+                    ptr[1] = data[2];
+                    ptr[2] = data[3];
+                    ptr[3] = data[4];
+                    ptr[4] = data[5];
+                    ptr[5] = data[6];
+                    ptr[6] = data[7];
+                    ptr[7] = data[8];
+                    value = returnValue;
+                    return;
             }
 
-            value = returnValue >> 3;
+            value = returnValue >> 4;
         }
 #endif
-        private static void ReadUInt64Packed(FastBufferReader reader, out ulong value)
-        {
-            reader.ReadByteSafe(out byte firstByte);
-            if (firstByte <= 240)
-            {
-                value = firstByte;
-                return;
-            }
-
-            if (firstByte <= 248)
-            {
-                reader.ReadByteSafe(out byte secondByte);
-                value = 240UL + ((firstByte - 241UL) << 8) + secondByte;
-                return;
-            }
-
-            var numBytes = firstByte - 247;
-            if (!reader.TryBeginReadInternal(numBytes))
-            {
-                throw new OverflowException("Reading past the end of the buffer");
-            }
-            reader.ReadPartialValue(out value, numBytes);
-        }
-
-        private static void ReadUInt32Packed(FastBufferReader reader, out uint value)
-        {
-            reader.ReadByteSafe(out byte firstByte);
-            if (firstByte <= 240)
-            {
-                value = firstByte;
-                return;
-            }
-
-            if (firstByte <= 248)
-            {
-                reader.ReadByteSafe(out byte secondByte);
-                value = 240U + ((firstByte - 241U) << 8) + secondByte;
-                return;
-            }
-
-            var numBytes = firstByte - 247;
-            if (!reader.TryBeginReadInternal(numBytes))
-            {
-                throw new OverflowException("Reading past the end of the buffer");
-            }
-            reader.ReadPartialValue(out value, numBytes);
-        }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static unsafe float ToSingle<T>(T value) where T : unmanaged

Runtime/Serialization/ByteUtility.cs

@@ -0,0 +1,58 @@
+using System.Runtime.CompilerServices;
+
+namespace Unity.Netcode
+{
+    internal class ByteUtility
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe byte ToByte(bool b) => *(byte*)&b;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool GetBit(byte bitField, ushort bitPosition)
+        {
+            return (bitField & (1 << bitPosition)) != 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static void SetBit(ref byte bitField, ushort bitPosition, bool value)
+        {
+            bitField = (byte)((bitField & ~(1 << bitPosition)) | (ToByte(value) << bitPosition));
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool GetBit(ushort bitField, ushort bitPosition)
+        {
+            return (bitField & (1 << bitPosition)) != 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static void SetBit(ref ushort bitField, ushort bitPosition, bool value)
+        {
+            bitField = (ushort)((bitField & ~(1 << bitPosition)) | (ToByte(value) << bitPosition));
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool GetBit(uint bitField, ushort bitPosition)
+        {
+            return (bitField & (1 << bitPosition)) != 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static void SetBit(ref uint bitField, ushort bitPosition, bool value)
+        {
+            bitField = (uint)((bitField & ~(1 << bitPosition)) | ((uint)ToByte(value) << bitPosition));
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool GetBit(ulong bitField, ushort bitPosition)
+        {
+            return (bitField & (ulong)(1 << bitPosition)) != 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static void SetBit(ref ulong bitField, ushort bitPosition, bool value)
+        {
+            bitField = ((bitField & (ulong)~(1 << bitPosition)) | ((ulong)ToByte(value) << bitPosition));
+        }
+    }
+}

Runtime/Serialization/ByteUtility.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 25bb0dd7157c423b8cfe0ecf06e15ae5
+timeCreated: 1666711082

Runtime/Serialization/FastBufferReader.cs

@@ -6,6 +6,12 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Optimized class used for reading values from a byte stream
+    /// <seealso cref="FastBufferWriter"/>
+    /// <seealso cref="BytePacker"/>
+    /// <seealso cref="ByteUnpacker"/>
+    /// </summary>
     public struct FastBufferReader : IDisposable
     {
         internal struct ReaderHandle
@@ -59,7 +65,7 @@ namespace Unity.Netcode
             ReaderHandle* readerHandle = null;
             if (copyAllocator == Allocator.None)
             {
-                readerHandle = (ReaderHandle*)UnsafeUtility.Malloc(sizeof(ReaderHandle) + length, UnsafeUtility.AlignOf<byte>(), internalAllocator);
+                readerHandle = (ReaderHandle*)UnsafeUtility.Malloc(sizeof(ReaderHandle), UnsafeUtility.AlignOf<byte>(), internalAllocator);
                 readerHandle->BufferPointer = buffer;
                 readerHandle->Position = offset;
             }
@@ -87,15 +93,15 @@ namespace Unity.Netcode
         /// <summary>
         /// Create a FastBufferReader from a NativeArray.
         ///
-        /// A new buffer will be created using the given <param name="copyAllocator"> and the value will be copied in.
+        /// A new buffer will be created using the given <param name="copyAllocator"></param> and the value will be copied in.
         /// FastBufferReader will then own the data.
         ///
-        /// The exception to this is when the <param name="copyAllocator"> passed in is Allocator.None. In this scenario,
+        /// The exception to this is when the <param name="copyAllocator"></param> passed in is Allocator.None. In this scenario,
         /// ownership of the data remains with the caller and the reader will point at it directly.
         /// When created with Allocator.None, FastBufferReader will allocate some internal data using
         /// Allocator.Temp so it should be treated as if it's a ref struct and not allowed to outlive
         /// the context in which it was created (it should neither be returned from that function nor
-        /// stored anywhere in heap memory). This is true, unless the <param name="internalAllocator"> param is explicitly set
+        /// stored anywhere in heap memory). This is true, unless the <param name="internalAllocator"></param> param is explicitly set
         /// to i.e.: Allocator.Persistent in which case it would allow the internal data to Persist for longer, but the caller
         /// should manually call Dispose() when it is no longer needed.
         /// </summary>
@@ -162,15 +168,15 @@ namespace Unity.Netcode
         /// <summary>
         /// Create a FastBufferReader from an existing byte buffer.
         ///
-        /// A new buffer will be created using the given <param name="copyAllocator"> and the value will be copied in.
+        /// A new buffer will be created using the given <param name="copyAllocator"></param> and the value will be copied in.
         /// FastBufferReader will then own the data.
         ///
-        /// The exception to this is when the <param name="copyAllocator"> passed in is Allocator.None. In this scenario,
+        /// The exception to this is when the <param name="copyAllocator"></param> passed in is Allocator.None. In this scenario,
         /// ownership of the data remains with the caller and the reader will point at it directly.
         /// When created with Allocator.None, FastBufferReader will allocate some internal data using
         /// Allocator.Temp, so it should be treated as if it's a ref struct and not allowed to outlive
         /// the context in which it was created (it should neither be returned from that function nor
-        /// stored anywhere in heap memory). This is true, unless the <param name="internalAllocator"> param is explicitly set
+        /// stored anywhere in heap memory). This is true, unless the <param name="internalAllocator"></param> param is explicitly set
         /// to i.e.: Allocator.Persistent in which case it would allow the internal data to Persist for longer, but the caller
         /// should manually call Dispose() when it is no longer needed.
         /// </summary>
@@ -187,15 +193,15 @@ namespace Unity.Netcode
         /// <summary>
         /// Create a FastBufferReader from a FastBufferWriter.
         ///
-        /// A new buffer will be created using the given <param name="copyAllocator"> and the value will be copied in.
+        /// A new buffer will be created using the given <param name="copyAllocator"></param> and the value will be copied in.
         /// FastBufferReader will then own the data.
         ///
-        /// The exception to this is when the <param name="copyAllocator"> passed in is Allocator.None. In this scenario,
+        /// The exception to this is when the <param name="copyAllocator"></param> passed in is Allocator.None. In this scenario,
         /// ownership of the data remains with the caller and the reader will point at it directly.
         /// When created with Allocator.None, FastBufferReader will allocate some internal data using
         /// Allocator.Temp, so it should be treated as if it's a ref struct and not allowed to outlive
         /// the context in which it was created (it should neither be returned from that function nor
-        /// stored anywhere in heap memory). This is true, unless the <param name="internalAllocator"> param is explicitly set
+        /// stored anywhere in heap memory). This is true, unless the <param name="internalAllocator"></param> param is explicitly set
         /// to i.e.: Allocator.Persistent in which case it would allow the internal data to Persist for longer, but the caller
         /// should manually call Dispose() when it is no longer needed.
         /// </summary>
@@ -214,10 +220,10 @@ namespace Unity.Netcode
         /// want to change the copyAllocator that a reader is allocated to - for example, upgrading a Temp reader to
         /// a Persistent one to be processed later.
         ///
-        /// A new buffer will be created using the given <param name="copyAllocator"> and the value will be copied in.
+        /// A new buffer will be created using the given <param name="copyAllocator"></param> and the value will be copied in.
         /// FastBufferReader will then own the data.
         ///
-        /// The exception to this is when the <param name="copyAllocator"> passed in is Allocator.None. In this scenario,
+        /// The exception to this is when the <param name="copyAllocator"></param> passed in is Allocator.None. In this scenario,
         /// ownership of the data remains with the caller and the reader will point at it directly.
         /// When created with Allocator.None, FastBufferReader will allocate some internal data using
         /// Allocator.Temp, so it should be treated as if it's a ref struct and not allowed to outlive
@@ -235,7 +241,7 @@ namespace Unity.Netcode
         }
 
         /// <summary>
-        /// Frees the allocated buffer
+        /// <see cref="IDisposable"/> implementation that frees the allocated buffer
         /// </summary>
         public unsafe void Dispose()
         {
@@ -335,6 +341,7 @@ namespace Unity.Netcode
         /// for performance reasons, since the point of using TryBeginRead is to avoid bounds checking in the following
         /// operations in release builds.
         /// </summary>
+        /// <typeparam name="T">the type `T` of the value you are trying to read</typeparam>
         /// <param name="value">The value you want to read</param>
         /// <returns>True if the read is allowed, false otherwise</returns>
         /// <exception cref="InvalidOperationException">If called while in a bitwise context</exception>
@@ -364,7 +371,7 @@ namespace Unity.Netcode
         /// Differs from TryBeginRead only in that it won't ever move the AllowedReadMark backward.
         /// </summary>
         /// <param name="bytes"></param>
-        /// <returns></returns>
+        /// <returns>true upon success</returns>
         /// <exception cref="InvalidOperationException"></exception>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal unsafe bool TryBeginReadInternal(int bytes)
@@ -393,7 +400,7 @@ namespace Unity.Netcode
         /// Returns an array representation of the underlying byte buffer.
         /// !!Allocates a new array!!
         /// </summary>
-        /// <returns></returns>
+        /// <returns>byte array</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe byte[] ToArray()
         {
@@ -408,7 +415,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Gets a direct pointer to the underlying buffer
         /// </summary>
-        /// <returns></returns>
+        /// <returns><see cref="byte"/> pointer</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe byte* GetUnsafePtr()
         {
@@ -418,7 +425,7 @@ namespace Unity.Netcode
         /// <summary>
         /// Gets a direct pointer to the underlying buffer at the current read position
         /// </summary>
-        /// <returns></returns>
+        /// <returns><see cref="byte"/> pointer</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe byte* GetUnsafePtrAtCurrentPosition()
         {
@@ -428,8 +435,8 @@ namespace Unity.Netcode
         /// <summary>
         /// Read an INetworkSerializable
         /// </summary>
-        /// <param name="value">INetworkSerializable instance</param>
         /// <typeparam name="T"></typeparam>
+        /// <param name="value">INetworkSerializable instance</param>
         /// <exception cref="NotImplementedException"></exception>
         public void ReadNetworkSerializable<T>(out T value) where T : INetworkSerializable, new()
         {
@@ -442,7 +449,7 @@ namespace Unity.Netcode
         /// Read an array of INetworkSerializables
         /// </summary>
         /// <param name="value">INetworkSerializable instance</param>
-        /// <typeparam name="T"></typeparam>
+        /// <typeparam name="T">the array to read the values of type `T` into</typeparam>
         /// <exception cref="NotImplementedException"></exception>
         public void ReadNetworkSerializable<T>(out T[] value) where T : INetworkSerializable, new()
         {
@@ -454,6 +461,19 @@ namespace Unity.Netcode
             }
         }
 
+        /// <summary>
+        /// Read an INetworkSerializable in-place, without constructing a new one
+        /// Note that this will NOT check for null before calling NetworkSerialize
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="value">INetworkSerializable instance</param>
+        /// <exception cref="NotImplementedException"></exception>
+        public void ReadNetworkSerializableInPlace<T>(ref T value) where T : INetworkSerializable
+        {
+            var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(this));
+            value.NetworkSerialize(bufferSerializer);
+        }
+
         /// <summary>
         /// Reads a string
         /// NOTE: ALLOCATES
@@ -537,7 +557,7 @@ namespace Unity.Netcode
         /// <param name="value">Value to read</param>
         /// <param name="bytesToRead">Number of bytes</param>
         /// <param name="offsetBytes">Offset into the value to write the bytes</param>
-        /// <typeparam name="T"></typeparam>
+        /// <typeparam name="T">the type value to read the value into</typeparam>
         /// <exception cref="InvalidOperationException"></exception>
         /// <exception cref="OverflowException"></exception>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -738,127 +758,522 @@ namespace Unity.Netcode
             }
         }
 
+        /// <summary>
+        /// Read a NetworkSerializable value
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => ReadNetworkSerializable(out value);
+
+        /// <summary>
+        /// Read a NetworkSerializable array
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T[] value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => ReadNetworkSerializable(out value);
 
+        /// <summary>
+        /// Read a NetworkSerializable value
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => ReadNetworkSerializable(out value);
+
+        /// <summary>
+        /// Read a NetworkSerializable array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T[] value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new() => ReadNetworkSerializable(out value);
 
+
+        /// <summary>
+        /// Read a struct
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a struct array
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => ReadUnmanaged(out value);
 
+        /// <summary>
+        /// Read a struct
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a struct array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => ReadUnmanagedSafe(out value);
 
+        /// <summary>
+        /// Read a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a primitive value array (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T[] value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => ReadUnmanaged(out value);
 
+        /// <summary>
+        /// Read a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T[] value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => ReadUnmanagedSafe(out value);
 
+        /// <summary>
+        /// Read an enum value
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read an enum array
+        /// </summary>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue<T>(out T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => ReadUnmanaged(out value);
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
 
+        /// <summary>
+        /// Read an enum value
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => ReadUnmanagedSafe(out value);
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
 
+        /// <summary>
+        /// Read an enum array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe<T>(out T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum => ReadUnmanagedSafe(out value);
 
+        /// <summary>
+        /// Read a Vector2
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector2 value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector2 array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector2[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector3
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector3 value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector3 array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector3[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector2Int
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector2Int value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector2Int array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector2Int[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector3Int
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector3Int value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector3Int array
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector3Int[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector4
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector4 value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Vector4
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Vector4[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Quaternion
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Quaternion value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Quaternion array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Quaternion[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Color
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Color value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Color array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Color[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Color32
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Color32 value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Color32 array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Color32[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Ray
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Ray value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Ray array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Ray[] value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Ray2D
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Ray2D value) => ReadUnmanaged(out value);
+
+        /// <summary>
+        /// Read a Ray2D array
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValue(out Ray2D[] value) => ReadUnmanaged(out value);
 
+
+        /// <summary>
+        /// Read a Vector2
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector2 value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector2 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector2[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector3
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector3 value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector3 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector3[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector2Int
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector2Int value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector2Int array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector2Int[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector3Int
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector3Int value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector3Int array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector3Int[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector4
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector4 value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Vector4 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Vector4[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Quaternion
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Quaternion value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Quaternion array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Quaternion[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Color
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Color value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Collor array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Color[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Color32
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Color32 value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Color32 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Color32[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Ray
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Ray value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Ray array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Ray[] value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Ray2D
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Ray2D value) => ReadUnmanagedSafe(out value);
+
+        /// <summary>
+        /// Read a Ray2D array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the values to read</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void ReadValueSafe(out Ray2D[] value) => ReadUnmanagedSafe(out value);
 
@@ -868,6 +1283,17 @@ namespace Unity.Netcode
         // Those two are necessary to serialize FixedStrings efficiently
         // - otherwise we'd just be memcpying the whole thing even if
         // most of it isn't used.
+
+        /// <summary>
+        /// Read a FixedString value.
+        /// This method is a little difficult to use, since you have to know the size of the string before
+        /// reading it, but is useful when the string is a known, fixed size. Note that the size of the
+        /// string is also encoded, so the size to call TryBeginRead on is actually the fixed size (in bytes)
+        /// plus sizeof(int)
+        /// </summary>
+        /// <param name="value">the value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe void ReadValue<T>(out T value, FastBufferWriter.ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes
@@ -878,6 +1304,16 @@ namespace Unity.Netcode
             ReadBytes(value.GetUnsafePtr(), length);
         }
 
+
+        /// <summary>
+        /// Read a FixedString value.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe void ReadValueSafe<T>(out T value, FastBufferWriter.ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes
@@ -887,5 +1323,24 @@ namespace Unity.Netcode
             value.Length = length;
             ReadBytesSafe(value.GetUnsafePtr(), length);
         }
+
+
+        /// <summary>
+        /// Read a FixedString value.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple reads at once by calling TryBeginRead.
+        /// </summary>
+        /// <param name="value">the value to read</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe void ReadValueSafeInPlace<T>(ref T value, FastBufferWriter.ForFixedStrings unused = default)
+            where T : unmanaged, INativeList<byte>, IUTF8Bytes
+        {
+            ReadUnmanagedSafe(out int length);
+            value.Length = length;
+            ReadBytesSafe(value.GetUnsafePtr(), length);
+        }
     }
 }

Runtime/Serialization/FastBufferWriter.cs

@@ -6,6 +6,12 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Optimized class used for writing values into a byte stream
+    /// <seealso cref="FastBufferReader"/>
+    /// <seealso cref="BytePacker"/>
+    /// <seealso cref="ByteUnpacker"/>
+    /// </summary>
     public struct FastBufferWriter : IDisposable
     {
         internal struct WriterHandle
@@ -108,7 +114,7 @@ namespace Unity.Netcode
         }
 
         /// <summary>
-        /// Frees the allocated buffer
+        /// <see cref="IDisposable"/> implementation that frees the allocated buffer
         /// </summary>
         public unsafe void Dispose()
         {
@@ -267,7 +273,8 @@ namespace Unity.Netcode
         /// operations in release builds. Instead, attempting to write past the marked position in release builds
         /// will write to random memory and cause undefined behavior, likely including instability and crashes.
         /// </summary>
-        /// <param name="value">The value you want to write</param>
+        /// <typeparam name="T">The value type to write</typeparam>
+        /// <param name="value">The value of the type `T` you want to write</param>
         /// <returns>True if the write is allowed, false otherwise</returns>
         /// <exception cref="InvalidOperationException">If called while in a bitwise context</exception>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -792,151 +799,590 @@ namespace Unity.Netcode
             }
         }
 
-        // These structs enable overloading of WriteValue with different generic constraints.
+        /// <summary>
-        // The compiler's actually able to distinguish between overloads based on generic constraints.
+        /// This empty struct exists to allow overloading WriteValue based on generic constraints.
-        // But at the bytecode level, the constraints aren't included in the method signature.
+        /// At the bytecode level, constraints aren't included in the method signature, so if multiple
-        // By adding a second parameter with a defaulted value, the signatures of each generic are different,
+        /// methods exist with the same signature, it causes a compile error because they would end up
-        // thus allowing overloads of methods based on the first parameter meeting constraints.
+        /// being emitted as the same method, even if the constraints are different.
+        /// Adding an empty struct with a default value gives them different signatures in the bytecode,
+        /// which then allows the compiler to do overload resolution based on the generic constraints
+        /// without the user having to pass the struct in themselves.
+        /// </summary>
         public struct ForPrimitives
         {
 
         }
 
+        /// <summary>
+        /// This empty struct exists to allow overloading WriteValue based on generic constraints.
+        /// At the bytecode level, constraints aren't included in the method signature, so if multiple
+        /// methods exist with the same signature, it causes a compile error because they would end up
+        /// being emitted as the same method, even if the constraints are different.
+        /// Adding an empty struct with a default value gives them different signatures in the bytecode,
+        /// which then allows the compiler to do overload resolution based on the generic constraints
+        /// without the user having to pass the struct in themselves.
+        /// </summary>
         public struct ForEnums
         {
 
         }
 
+        /// <summary>
+        /// This empty struct exists to allow overloading WriteValue based on generic constraints.
+        /// At the bytecode level, constraints aren't included in the method signature, so if multiple
+        /// methods exist with the same signature, it causes a compile error because they would end up
+        /// being emitted as the same method, even if the constraints are different.
+        /// Adding an empty struct with a default value gives them different signatures in the bytecode,
+        /// which then allows the compiler to do overload resolution based on the generic constraints
+        /// without the user having to pass the struct in themselves.
+        /// </summary>
         public struct ForStructs
         {
 
         }
 
+        /// <summary>
+        /// This empty struct exists to allow overloading WriteValue based on generic constraints.
+        /// At the bytecode level, constraints aren't included in the method signature, so if multiple
+        /// methods exist with the same signature, it causes a compile error because they would end up
+        /// being emitted as the same method, even if the constraints are different.
+        /// Adding an empty struct with a default value gives them different signatures in the bytecode,
+        /// which then allows the compiler to do overload resolution based on the generic constraints
+        /// without the user having to pass the struct in themselves.
+        /// </summary>
         public struct ForNetworkSerializable
         {
 
         }
 
+        /// <summary>
+        /// This empty struct exists to allow overloading WriteValue based on generic constraints.
+        /// At the bytecode level, constraints aren't included in the method signature, so if multiple
+        /// methods exist with the same signature, it causes a compile error because they would end up
+        /// being emitted as the same method, even if the constraints are different.
+        /// Adding an empty struct with a default value gives them different signatures in the bytecode,
+        /// which then allows the compiler to do overload resolution based on the generic constraints
+        /// without the user having to pass the struct in themselves.
+        /// </summary>
         public struct ForFixedStrings
         {
 
         }
 
+        /// <summary>
+        /// Write a NetworkSerializable value
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(in T value, ForNetworkSerializable unused = default) where T : INetworkSerializable => WriteNetworkSerializable(value);
+
+        /// <summary>
+        /// Write a NetworkSerializable array
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(T[] value, ForNetworkSerializable unused = default) where T : INetworkSerializable => WriteNetworkSerializable(value);
+
+        /// <summary>
+        /// Write a NetworkSerializable value
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(in T value, ForNetworkSerializable unused = default) where T : INetworkSerializable => WriteNetworkSerializable(value);
+
+        /// <summary>
+        /// Write a NetworkSerializable array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(T[] value, ForNetworkSerializable unused = default) where T : INetworkSerializable => WriteNetworkSerializable(value);
 
+        /// <summary>
+        /// Write a struct
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(in T value, ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a struct array
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(T[] value, ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a struct
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(in T value, ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a struct array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(T[] value, ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy => WriteUnmanagedSafe(value);
 
+        /// <summary>
+        /// Write a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(in T value, ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a primitive value array (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(T[] value, ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(in T value, ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(T[] value, ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T> => WriteUnmanagedSafe(value);
 
+        /// <summary>
+        /// Write an enum value
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(in T value, ForEnums unused = default) where T : unmanaged, Enum => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write an enum array
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue<T>(T[] value, ForEnums unused = default) where T : unmanaged, Enum => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write an enum value
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(in T value, ForEnums unused = default) where T : unmanaged, Enum => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write an enum array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">The values to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(T[] value, ForEnums unused = default) where T : unmanaged, Enum => WriteUnmanagedSafe(value);
 
+        /// <summary>
+        /// Write a Vector2
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Vector2 value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector2 array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Vector2[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector3
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Vector3 value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector3 array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Vector3[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector2Int
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Vector2Int value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector2Int array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Vector2Int[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector3Int
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Vector3Int value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector3Int array
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Vector3Int[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector4
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Vector4 value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Vector4
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Vector4[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Quaternion
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Quaternion value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Quaternion array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Quaternion[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Color
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Color value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Color array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Color[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Color32
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Color32 value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Color32 array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Color32[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Ray
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Ray value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Ray array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Ray[] value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Ray2D
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(in Ray2D value) => WriteUnmanaged(value);
+
+        /// <summary>
+        /// Write a Ray2D array
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValue(Ray2D[] value) => WriteUnmanaged(value);
 
+
+        /// <summary>
+        /// Write a Vector2
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Vector2 value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector2 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Vector2[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector3
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Vector3 value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector3 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Vector3[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector2Int
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Vector2Int value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector2Int array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Vector2Int[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector3Int
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Vector3Int value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector3Int array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Vector3Int[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector4
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Vector4 value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Vector4 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Vector4[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Quaternion
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Quaternion value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Quaternion array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Quaternion[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Color
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Color value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Collor array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Color[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Color32
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Color32 value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Color32 array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Color32[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Ray
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Ray value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Ray array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Ray[] value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Ray2D
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(in Ray2D value) => WriteUnmanagedSafe(value);
+
+        /// <summary>
+        /// Write a Ray2D array
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the values to write</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe(Ray2D[] value) => WriteUnmanagedSafe(value);
 
@@ -946,6 +1392,15 @@ namespace Unity.Netcode
         // Those two are necessary to serialize FixedStrings efficiently
         // - otherwise we'd just be memcpying the whole thing even if
         // most of it isn't used.
+
+        /// <summary>
+        /// Write a FixedString value. Writes only the part of the string that's actually used.
+        /// When calling TryBeginWrite, ensure you calculate the write size correctly (preferably by calling
+        /// FastBufferWriter.GetWriteSize())
+        /// </summary>
+        /// <param name="value">the value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe void WriteValue<T>(in T value, ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes
@@ -960,6 +1415,16 @@ namespace Unity.Netcode
             }
         }
 
+
+        /// <summary>
+        /// Write a FixedString value. Writes only the part of the string that's actually used.
+        ///
+        /// "Safe" version - automatically performs bounds checking. Less efficient than bounds checking
+        /// for multiple writes at once by calling TryBeginWrite.
+        /// </summary>
+        /// <param name="value">the value to write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueSafe<T>(in T value, ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes

Runtime/Serialization/ForceNetworkSerializeByMemcpy.cs

@@ -9,26 +9,58 @@ namespace Unity.Netcode
     /// <typeparam name="T"></typeparam>
     public struct ForceNetworkSerializeByMemcpy<T> : INetworkSerializeByMemcpy, IEquatable<ForceNetworkSerializeByMemcpy<T>> where T : unmanaged, IEquatable<T>
     {
+        /// <summary>
+        /// The wrapped value
+        /// </summary>
         public T Value;
 
+        /// <summary>
+        /// The default constructor for <see cref="ForceNetworkSerializeByMemcpy{T}"/>
+        /// </summary>
+        /// <param name="value">sets the initial value of type `T`</param>
         public ForceNetworkSerializeByMemcpy(T value)
         {
             Value = value;
         }
 
+        /// <summary>
+        /// Convert implicitly from the ForceNetworkSerializeByMemcpy wrapper to the underlying value
+        /// </summary>
+        /// <param name="container">The wrapper</param>
+        /// <returns>The underlying value</returns>
         public static implicit operator T(ForceNetworkSerializeByMemcpy<T> container) => container.Value;
+
+        /// <summary>
+        /// Convert implicitly from a T value to a ForceNetworkSerializeByMemcpy wrapper
+        /// </summary>
+        /// <param name="underlyingValue">the value</param>
+        /// <returns>a new wrapper</returns>
         public static implicit operator ForceNetworkSerializeByMemcpy<T>(T underlyingValue) => new ForceNetworkSerializeByMemcpy<T> { Value = underlyingValue };
 
+        /// <summary>
+        /// Check if wrapped values are equal
+        /// </summary>
+        /// <param name="other">Other wrapper</param>
+        /// <returns>true if equal</returns>
         public bool Equals(ForceNetworkSerializeByMemcpy<T> other)
         {
             return Value.Equals(other.Value);
         }
 
+        /// <summary>
+        /// Check if this value is equal to a boxed object value
+        /// </summary>
+        /// <param name="obj">The boxed value to check against</param>
+        /// <returns>true if equal</returns>
         public override bool Equals(object obj)
         {
             return obj is ForceNetworkSerializeByMemcpy<T> other && Equals(other);
         }
 
+        /// <summary>
+        /// Obtains the wrapped value's hash code
+        /// </summary>
+        /// <returns>Wrapped value's hash code</returns>
         public override int GetHashCode()
         {
             return Value.GetHashCode();

Runtime/Serialization/INetworkSerializeByMemcpy.cs

@@ -6,7 +6,7 @@ namespace Unity.Netcode
     /// by memcpy. It's up to the developer of the struct to analyze the struct's contents and ensure it
     /// is actually serializable by memcpy. This requires all of the members of the struct to be
     /// `unmanaged` Plain-Old-Data values - if your struct contains a pointer (or a type that contains a pointer,
-    /// like `NativeList<T>`), it should be serialized via `INetworkSerializable` or via
+    /// like `NativeList&lt;T&gt;`), it should be serialized via `INetworkSerializable` or via
     /// `FastBufferReader`/`FastBufferWriter` extension methods.
     /// </summary>
     public interface INetworkSerializeByMemcpy

Runtime/Serialization/IReaderWriter.cs

@@ -4,81 +4,536 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Interface for an implementation of one side of a two-way serializer
+    /// </summary>
     public interface IReaderWriter
     {
+        /// <summary>
+        /// Check whether this implementation is a "reader" - if it's been constructed to deserialize data
+        /// </summary>
         bool IsReader { get; }
+        /// <summary>
+        /// Check whether this implementation is a "writer" - if it's been constructed to serialize data
+        /// </summary>
         bool IsWriter { get; }
 
+        /// <summary>
+        /// Get the underlying FastBufferReader struct.
+        /// Only valid when IsReader == true
+        /// </summary>
+        /// <returns>underlying FastBufferReader</returns>
         FastBufferReader GetFastBufferReader();
+        /// <summary>
+        /// Get the underlying FastBufferWriter struct.
+        /// Only valid when IsWriter == true
+        /// </summary>
+        /// <returns>underlying FastBufferWriter</returns>
         FastBufferWriter GetFastBufferWriter();
 
+        /// <summary>
+        /// Read or write a string
+        /// </summary>
+        /// <param name="s">The value to read/write</param>
+        /// <param name="oneByteChars">If true, characters will be limited to one-byte ASCII characters</param>
         void SerializeValue(ref string s, bool oneByteChars = false);
+
+        /// <summary>
+        /// Read or write a single byte
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref byte value);
+
+        /// <summary>
+        /// Read or write a primitive value (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T>;
+
+        /// <summary>
+        /// Read or write an array of primitive values (int, bool, etc)
+        /// Accepts any value that implements the given interfaces, but is not guaranteed to work correctly
+        /// on values that are not primitives.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T[] value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T>;
+
+        /// <summary>
+        /// Read or write an enum value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum;
+
+        /// <summary>
+        /// Read or write an array of enum values
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum;
+
+        /// <summary>
+        /// Read or write a struct value implementing ISerializeByMemcpy
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy;
+
+        /// <summary>
+        /// Read or write an array of struct values implementing ISerializeByMemcpy
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy;
+
+        /// <summary>
+        /// Read or write a struct or class value implementing INetworkSerializable
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new();
+
+        /// <summary>
+        /// Read or write an array of struct or class values implementing INetworkSerializable
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T[] value, FastBufferWriter.ForNetworkSerializable unused = default) where T : INetworkSerializable, new();
+
+        /// <summary>
+        /// Read or write a FixedString value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter used for enabling overload resolution based on generic constraints</param>
+        /// <typeparam name="T">The type being serialized</typeparam>
         void SerializeValue<T>(ref T value, FastBufferWriter.ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes;
+
+        /// <summary>
+        /// Read or write a Vector2 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Vector2 value);
+
+        /// <summary>
+        /// Read or write an array of Vector2 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Vector2[] value);
+
+        /// <summary>
+        /// Read or write a Vector3 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Vector3 value);
+
+        /// <summary>
+        /// Read or write an array of Vector3 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Vector3[] value);
+
+        /// <summary>
+        /// Read or write a Vector2Int value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Vector2Int value);
+
+        /// <summary>
+        /// Read or write an array of Vector2Int values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Vector2Int[] value);
+
+        /// <summary>
+        /// Read or write a Vector3Int value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Vector3Int value);
+
+        /// <summary>
+        /// Read or write an array of Vector3Int values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Vector3Int[] value);
+
+        /// <summary>
+        /// Read or write a Vector4 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Vector4 value);
+
+        /// <summary>
+        /// Read or write an array of Vector4 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Vector4[] value);
+
+        /// <summary>
+        /// Read or write a Quaternion value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Quaternion value);
+
+        /// <summary>
+        /// Read or write an array of Quaternion values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Quaternion[] value);
+
+        /// <summary>
+        /// Read or write a Color value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Color value);
+
+        /// <summary>
+        /// Read or write an array of Color values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Color[] value);
+
+        /// <summary>
+        /// Read or write a Color32 value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Color32 value);
+
+        /// <summary>
+        /// Read or write an array of Color32 values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Color32[] value);
+
+        /// <summary>
+        /// Read or write a Ray value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Ray value);
+
+        /// <summary>
+        /// Read or write an array of Ray values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Ray[] value);
+
+        /// <summary>
+        /// Read or write a Ray2D value
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValue(ref Ray2D value);
+
+        /// <summary>
+        /// Read or write an array of Ray2D values
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValue(ref Ray2D[] value);
 
-        // Has to have a different name to avoid conflicting with "where T: unmananged"
+        /// <summary>
+        /// Read or write a NetworkSerializable value.
+        /// SerializeValue() is the preferred method to do this - this is provided for backward compatibility only.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
+        /// <typeparam name="T">The network serializable type</typeparam>
         void SerializeNetworkSerializable<T>(ref T value) where T : INetworkSerializable, new();
 
+        /// <summary>
+        /// Performs an advance check to ensure space is available to read/write one or more values.
+        /// This provides a performance benefit for serializing multiple values using the
+        /// SerializeValuePreChecked methods. But note that the benefit is small and only likely to be
+        /// noticeable if serializing a very large number of items.
+        /// </summary>
+        /// <param name="amount"></param>
+        /// <returns></returns>
         bool PreCheck(int amount);
+
+        /// <summary>
+        /// Serialize a string, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="s">The value to read/write</param>
+        /// <param name="oneByteChars">If true, characters will be limited to one-byte ASCII characters</param>
         void SerializeValuePreChecked(ref string s, bool oneByteChars = false);
+
+        /// <summary>
+        /// Serialize a byte, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref byte value);
+
+        /// <summary>
+        /// Serialize a primitive, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T>;
+
+        /// <summary>
+        /// Serialize an array of primitives, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T[] value, FastBufferWriter.ForPrimitives unused = default) where T : unmanaged, IComparable, IConvertible, IComparable<T>, IEquatable<T>;
+
+        /// <summary>
+        /// Serialize an enum, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum;
+
+        /// <summary>
+        /// Serialize an array of enums, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T[] value, FastBufferWriter.ForEnums unused = default) where T : unmanaged, Enum;
+
+        /// <summary>
+        /// Serialize a struct, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy;
+
+        /// <summary>
+        /// Serialize an array of structs, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The values to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T[] value, FastBufferWriter.ForStructs unused = default) where T : unmanaged, INetworkSerializeByMemcpy;
+
+        /// <summary>
+        /// Serialize a FixedString, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <typeparam name="T">The type being serialized</typeparam>
+        /// <param name="value">The value to read/write</param>
+        /// <param name="unused">An unused parameter that can be used for enabling overload resolution based on generic constraints</param>
         void SerializeValuePreChecked<T>(ref T value, FastBufferWriter.ForFixedStrings unused = default)
             where T : unmanaged, INativeList<byte>, IUTF8Bytes;
 
+        /// <summary>
+        /// Serialize a Vector2, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector2 value);
+
+        /// <summary>
+        /// Serialize a Vector2 array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValuePreChecked(ref Vector2[] value);
+
+        /// <summary>
+        /// Serialize a Vector3, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector3 value);
+
+        /// <summary>
+        /// Serialize a Vector3 array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValuePreChecked(ref Vector3[] value);
+
+        /// <summary>
+        /// Serialize a Vector2Int, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector2Int value);
+
+        /// <summary>
+        /// Serialize a Vector2Int array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The values to read/write</param>
         void SerializeValuePreChecked(ref Vector2Int[] value);
+
+        /// <summary>
+        /// Serialize a Vector3Int, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector3Int value);
+
+        /// <summary>
+        /// Serialize a Vector3Int array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector3Int[] value);
+
+        /// <summary>
+        /// Serialize a Vector4, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector4 value);
+
+        /// <summary>
+        /// Serialize a Vector4Array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Vector4[] value);
+
+        /// <summary>
+        /// Serialize a Quaternion, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Quaternion value);
+
+        /// <summary>
+        /// Serialize a Quaternion array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Quaternion[] value);
+
+        /// <summary>
+        /// Serialize a Color, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Color value);
+
+        /// <summary>
+        /// Serialize a Color array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Color[] value);
+
+        /// <summary>
+        /// Serialize a Color32, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Color32 value);
+
+        /// <summary>
+        /// Serialize a Color32 array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Color32[] value);
+
+        /// <summary>
+        /// Serialize a Ray, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Ray value);
+
+        /// <summary>
+        /// Serialize a Ray array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Ray[] value);
+
+        /// <summary>
+        /// Serialize a Ray2D, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Ray2D value);
+
+        /// <summary>
+        /// Serialize a Ray2D array, "pre-checked", which skips buffer checks.
+        /// In debug and editor builds, a check is made to ensure you've called "PreCheck" before
+        /// calling this. In release builds, calling this without calling "PreCheck" may read or write
+        /// past the end of the buffer, which will cause memory corruption and undefined behavior.
+        /// </summary>
+        /// <param name="value">The value to read/write</param>
         void SerializeValuePreChecked(ref Ray2D[] value);
     }
 }

Runtime/Serialization/NetworkBehaviourReference.cs

@@ -96,8 +96,18 @@ namespace Unity.Netcode
             serializer.SerializeValue(ref m_NetworkBehaviourId);
         }
 
+        /// <summary>
+        /// Implicitly convert <see cref="NetworkBehaviourReference"/> to <see cref="NetworkBehaviour"/>.
+        /// </summary>
+        /// <param name="networkBehaviourRef">The <see cref="NetworkBehaviourReference"/> to convert from.</param>
+        /// <returns>The <see cref="NetworkBehaviour"/> this class is holding a reference to</returns>
         public static implicit operator NetworkBehaviour(NetworkBehaviourReference networkBehaviourRef) => GetInternal(networkBehaviourRef);
 
+        /// <summary>
+        /// Implicitly convert <see cref="NetworkBehaviour"/> to <see cref="NetworkBehaviourReference"/>.
+        /// </summary>
+        /// <param name="networkBehaviour">The <see cref="NetworkBehaviour"/> to convert from.</param>
+        /// <returns>The <see cref="NetworkBehaviourReference"/> created from the <see cref="NetworkBehaviour"/> passed in as a parameter</returns>
         public static implicit operator NetworkBehaviourReference(NetworkBehaviour networkBehaviour) => new NetworkBehaviourReference(networkBehaviour);
     }
 }

Runtime/Serialization/NetworkObjectReference.cs

@@ -120,12 +120,41 @@ namespace Unity.Netcode
             serializer.SerializeValue(ref m_NetworkObjectId);
         }
 
+        /// <summary>
+        /// Implicitly convert <see cref="NetworkObjectReference"/> to <see cref="NetworkObject"/>.
+        /// </summary>
+        /// <param name="networkObjectRef">The <see cref="NetworkObjectReference"/> to convert from.</param>
+        /// <returns>The <see cref="NetworkObject"/> the <see cref="NetworkObjectReference"/> is referencing</returns>
         public static implicit operator NetworkObject(NetworkObjectReference networkObjectRef) => Resolve(networkObjectRef);
 
+        /// <summary>
+        /// Implicitly convert <see cref="NetworkObject"/> to <see cref="NetworkObjectReference"/>.
+        /// </summary>
+        /// <param name="networkObject">The <see cref="NetworkObject"/> to convert from.</param>
+        /// <returns>The <see cref="NetworkObjectReference"/> created from the <see cref="NetworkObject"/> parameter</returns>
         public static implicit operator NetworkObjectReference(NetworkObject networkObject) => new NetworkObjectReference(networkObject);
 
-        public static implicit operator GameObject(NetworkObjectReference networkObjectRef) => Resolve(networkObjectRef).gameObject;
+        /// <summary>
+        /// Implicitly convert <see cref="NetworkObjectReference"/> to <see cref="GameObject"/>.
+        /// </summary>
+        /// <param name="networkObjectRef">The <see cref="NetworkObjectReference"/> to convert from.</param>
+        /// <returns>This returns the <see cref="GameObject"/> that the <see cref="NetworkObject"/> is attached to and is referenced by the <see cref="NetworkObjectReference"/> passed in as a parameter</returns>
+        public static implicit operator GameObject(NetworkObjectReference networkObjectRef)
+        {
+            var networkObject = Resolve(networkObjectRef);
+            if (networkObject != null)
+            {
+                return networkObject.gameObject;
+            }
 
+            return null;
+        }
+
+        /// <summary>
+        /// Implicitly convert <see cref="GameObject"/> to <see cref="NetworkObject"/>.
+        /// </summary>
+        /// <param name="gameObject">The <see cref="GameObject"/> to convert from.</param>
+        /// <returns>The <see cref="NetworkObjectReference"/> created from the <see cref="GameObject"/> parameter that has a <see cref="NetworkObject"/> component attached to it</returns>
         public static implicit operator NetworkObjectReference(GameObject gameObject) => new NetworkObjectReference(gameObject);
     }
 }

Runtime/Spawning/NetworkPrefabHandler.cs

@@ -119,8 +119,7 @@ namespace Unity.Netcode
                         // Now we register all
                         foreach (var gameObject in networkPrefabOverrides)
                         {
-                            var targetNetworkObject = gameObject.GetComponent<NetworkObject>();
+                            if (gameObject.TryGetComponent<NetworkObject>(out var targetNetworkObject))
-                            if (targetNetworkObject != null)
                             {
                                 if (!m_PrefabInstanceToPrefabAsset.ContainsKey(targetNetworkObject.GlobalObjectIdHash))
                                 {

Runtime/Spawning/NetworkSpawnManager.cs

@@ -126,6 +126,7 @@ namespace Unity.Netcode
         /// Returns a list of all NetworkObjects that belong to a client.
         /// </summary>
         /// <param name="clientId">the client's id  <see cref="NetworkManager.LocalClientId"/></param>
+        /// <returns>returns the list of <see cref="NetworkObject"/>s owned by the client</returns>
         public List<NetworkObject> GetClientOwnedObjects(ulong clientId)
         {
             if (!OwnershipToObjectsTable.ContainsKey(clientId))
@@ -172,9 +173,11 @@ namespace Unity.Netcode
             return GetPlayerNetworkObject(NetworkManager.LocalClientId);
         }
 
+
         /// <summary>
         /// Returns the player object with a given clientId or null if one does not exist. This is only valid server side.
         /// </summary>
+        /// <param name="clientId">the client identifier of the player</param>
         /// <returns>The player object with a given clientId or null if one does not exist</returns>
         public NetworkObject GetPlayerNetworkObject(ulong clientId)
         {
@@ -210,11 +213,11 @@ namespace Unity.Netcode
                 return;
             }
 
+            networkObject.OwnerClientId = NetworkManager.ServerClientId;
+
             // Server removes the entry and takes over ownership before notifying
             UpdateOwnershipTable(networkObject, NetworkManager.ServerClientId, true);
 
-            networkObject.OwnerClientId = NetworkManager.ServerClientId;
-
             var message = new ChangeOwnershipMessage
             {
                 NetworkObjectId = networkObject.NetworkObjectId,
@@ -267,6 +270,9 @@ namespace Unity.Netcode
 
             networkObject.OwnerClientId = clientId;
 
+            networkObject.MarkVariablesDirty(true);
+            NetworkManager.BehaviourUpdater.AddForUpdate(networkObject);
+
             // Server adds entries for all client ownership
             UpdateOwnershipTable(networkObject, networkObject.OwnerClientId);
 
@@ -275,23 +281,26 @@ namespace Unity.Netcode
                 NetworkObjectId = networkObject.NetworkObjectId,
                 OwnerClientId = networkObject.OwnerClientId
             };
-            var size = NetworkManager.SendMessage(ref message, NetworkDelivery.ReliableSequenced, NetworkManager.ConnectedClientsIds);
 
             foreach (var client in NetworkManager.ConnectedClients)
             {
+                if (networkObject.IsNetworkVisibleTo(client.Value.ClientId))
+                {
+                    var size = NetworkManager.SendMessage(ref message, NetworkDelivery.ReliableSequenced, client.Value.ClientId);
                     NetworkManager.NetworkMetrics.TrackOwnershipChangeSent(client.Key, networkObject, size);
                 }
             }
+        }
 
         internal bool HasPrefab(NetworkObject.SceneObject sceneObject)
         {
-            if (!NetworkManager.NetworkConfig.EnableSceneManagement || !sceneObject.Header.IsSceneObject)
+            if (!NetworkManager.NetworkConfig.EnableSceneManagement || !sceneObject.IsSceneObject)
             {
-                if (NetworkManager.PrefabHandler.ContainsHandler(sceneObject.Header.Hash))
+                if (NetworkManager.PrefabHandler.ContainsHandler(sceneObject.Hash))
                 {
                     return true;
                 }
-                if (NetworkManager.NetworkConfig.NetworkPrefabOverrideLinks.TryGetValue(sceneObject.Header.Hash, out var networkPrefab))
+                if (NetworkManager.NetworkConfig.NetworkPrefabOverrideLinks.TryGetValue(sceneObject.Hash, out var networkPrefab))
                 {
                     switch (networkPrefab.Override)
                     {
@@ -306,53 +315,38 @@ namespace Unity.Netcode
 
                 return false;
             }
-            var networkObject = NetworkManager.SceneManager.GetSceneRelativeInSceneNetworkObject(sceneObject.Header.Hash, sceneObject.NetworkSceneHandle);
+            var networkObject = NetworkManager.SceneManager.GetSceneRelativeInSceneNetworkObject(sceneObject.Hash, sceneObject.NetworkSceneHandle);
             return networkObject != null;
         }
 
         /// <summary>
-        /// Should only run on the client
+        /// Creates a local NetowrkObject to be spawned.
         /// </summary>
-        internal NetworkObject CreateLocalNetworkObject(bool isSceneObject, uint globalObjectIdHash, ulong ownerClientId, ulong? parentNetworkId, int? networkSceneHandle, Vector3? position, Quaternion? rotation, bool isReparented = false)
+        /// <remarks>
+        /// For most cases this is client-side only, with the exception of when the server
+        /// is spawning a player.
+        /// </remarks>
+        internal NetworkObject CreateLocalNetworkObject(NetworkObject.SceneObject sceneObject)
         {
-            NetworkObject parentNetworkObject = null;
+            NetworkObject networkObject = null;
+            var globalObjectIdHash = sceneObject.Hash;
+            var position = sceneObject.HasTransform ? sceneObject.Transform.Position : default;
+            var rotation = sceneObject.HasTransform ? sceneObject.Transform.Rotation : default;
+            var scale = sceneObject.HasTransform ? sceneObject.Transform.Scale : default;
+            var parentNetworkId = sceneObject.HasParent ? sceneObject.ParentObjectId : default;
+            var worldPositionStays = (!sceneObject.HasParent) || sceneObject.WorldPositionStays;
+            var isSpawnedByPrefabHandler = false;
 
-            if (parentNetworkId != null && !isReparented)
+            // If scene management is disabled or the NetworkObject was dynamically spawned
-            {
+            if (!NetworkManager.NetworkConfig.EnableSceneManagement || !sceneObject.IsSceneObject)
-                if (SpawnedObjects.TryGetValue(parentNetworkId.Value, out NetworkObject networkObject))
-                {
-                    parentNetworkObject = networkObject;
-                }
-                else
-                {
-                    if (NetworkLog.CurrentLogLevel <= LogLevel.Normal)
-                    {
-                        NetworkLog.LogWarning("Cannot find parent. Parent objects always have to be spawned and replicated BEFORE the child");
-                    }
-                }
-            }
-
-            if (!NetworkManager.NetworkConfig.EnableSceneManagement || !isSceneObject)
             {
                 // If the prefab hash has a registered INetworkPrefabInstanceHandler derived class
                 if (NetworkManager.PrefabHandler.ContainsHandler(globalObjectIdHash))
                 {
                     // Let the handler spawn the NetworkObject
-                    var networkObject = NetworkManager.PrefabHandler.HandleNetworkPrefabSpawn(globalObjectIdHash, ownerClientId, position.GetValueOrDefault(Vector3.zero), rotation.GetValueOrDefault(Quaternion.identity));
+                    networkObject = NetworkManager.PrefabHandler.HandleNetworkPrefabSpawn(globalObjectIdHash, sceneObject.OwnerClientId, position, rotation);
-
                     networkObject.NetworkManagerOwner = NetworkManager;
-
+                    isSpawnedByPrefabHandler = true;
-                    if (parentNetworkObject != null)
-                    {
-                        networkObject.transform.SetParent(parentNetworkObject.transform, true);
-                    }
-
-                    if (NetworkSceneManager.IsSpawnedObjectsPendingInDontDestroyOnLoad)
-                    {
-                        UnityEngine.Object.DontDestroyOnLoad(networkObject.gameObject);
-                    }
-
-                    return networkObject;
                 }
                 else
                 {
@@ -380,31 +374,18 @@ namespace Unity.Netcode
                         {
                             NetworkLog.LogError($"Failed to create object locally. [{nameof(globalObjectIdHash)}={globalObjectIdHash}]. {nameof(NetworkPrefab)} could not be found. Is the prefab registered with {nameof(NetworkManager)}?");
                         }
-
-                        return null;
-                    }
-
-                    // Otherwise, instantiate an instance of the NetworkPrefab linked to the prefabHash
-                    var networkObject = ((position == null && rotation == null) ? UnityEngine.Object.Instantiate(networkPrefabReference) : UnityEngine.Object.Instantiate(networkPrefabReference, position.GetValueOrDefault(Vector3.zero), rotation.GetValueOrDefault(Quaternion.identity))).GetComponent<NetworkObject>();
-
-                    networkObject.NetworkManagerOwner = NetworkManager;
-
-                    if (parentNetworkObject != null)
-                    {
-                        networkObject.transform.SetParent(parentNetworkObject.transform, true);
-                    }
-
-                    if (NetworkSceneManager.IsSpawnedObjectsPendingInDontDestroyOnLoad)
-                    {
-                        UnityEngine.Object.DontDestroyOnLoad(networkObject.gameObject);
-                    }
-
-                    return networkObject;
-                }
                     }
                     else
                     {
-                var networkObject = NetworkManager.SceneManager.GetSceneRelativeInSceneNetworkObject(globalObjectIdHash, networkSceneHandle);
+                        // Create prefab instance
+                        networkObject = UnityEngine.Object.Instantiate(networkPrefabReference).GetComponent<NetworkObject>();
+                        networkObject.NetworkManagerOwner = NetworkManager;
+                    }
+                }
+            }
+            else // Get the in-scene placed NetworkObject
+            {
+                networkObject = NetworkManager.SceneManager.GetSceneRelativeInSceneNetworkObject(globalObjectIdHash, sceneObject.NetworkSceneHandle);
 
                 if (networkObject == null)
                 {
@@ -412,19 +393,91 @@ namespace Unity.Netcode
                     {
                         NetworkLog.LogError($"{nameof(NetworkPrefab)} hash was not found! In-Scene placed {nameof(NetworkObject)} soft synchronization failure for Hash: {globalObjectIdHash}!");
                     }
-
-                    return null;
                 }
 
-                if (parentNetworkObject != null)
+                // Since this NetworkObject is an in-scene placed NetworkObject, if it is disabled then enable it so
+                // NetworkBehaviours will have their OnNetworkSpawn method invoked
+                if (networkObject != null && !networkObject.gameObject.activeInHierarchy)
                 {
-                    networkObject.transform.SetParent(parentNetworkObject.transform, true);
+                    networkObject.gameObject.SetActive(true);
+                }
             }
 
-                return networkObject;
+            if (networkObject != null)
+            {
+                // SPECIAL CASE FOR IN-SCENE PLACED:  (only when the parent has a NetworkObject)
+                // This is a special case scenario where a late joining client has joined and loaded one or
+                // more scenes that contain nested in-scene placed NetworkObject children yet the server's
+                // synchronization information does not indicate the NetworkObject in question has a parent.
+                // Under this scenario, we want to remove the parent before spawning and setting the transform values.
+                if (sceneObject.IsSceneObject && !sceneObject.HasParent && networkObject.transform.parent != null)
+                {
+                    // if the in-scene placed NetworkObject has a parent NetworkObject but the synchronization information does not
+                    // include parenting, then we need to force the removal of that parent
+                    if (networkObject.transform.parent.GetComponent<NetworkObject>() != null)
+                    {
+                        // remove the parent
+                        networkObject.ApplyNetworkParenting(true, true);
                     }
                 }
 
+                // Set the transform unless we were spawned by a prefab handler
+                // Note: prefab handlers are provided the position and rotation
+                // but it is up to the user to set those values
+                if (sceneObject.HasTransform && !isSpawnedByPrefabHandler)
+                {
+                    // If world position stays is true or we have auto object parent synchronization disabled
+                    // then we want to apply the position and rotation values world space relative
+                    if (worldPositionStays || !networkObject.AutoObjectParentSync)
+                    {
+                        networkObject.transform.position = position;
+                        networkObject.transform.rotation = rotation;
+                    }
+                    else
+                    {
+                        networkObject.transform.localPosition = position;
+                        networkObject.transform.localRotation = rotation;
+                    }
+
+                    // SPECIAL CASE:
+                    // Since players are created uniquely we don't apply scale because
+                    // the ConnectionApprovalResponse does not currently provide the
+                    // ability to specify scale. So, we just use the default scale of
+                    // the network prefab used to represent the player.
+                    // Note: not doing this would set the player's scale to zero since
+                    // that is the default value of Vector3.
+                    if (!sceneObject.IsPlayerObject)
+                    {
+                        // Since scale is always applied to local space scale, we do the transform
+                        // space logic during serialization such that it works out whether AutoObjectParentSync
+                        // is enabled or not (see NetworkObject.SceneObject)
+                        networkObject.transform.localScale = scale;
+                    }
+                }
+
+                if (sceneObject.HasParent)
+                {
+                    // Go ahead and set network parenting properties, if the latest parent is not set then pass in null
+                    // (we always want to set worldPositionStays)
+                    ulong? parentId = null;
+                    if (sceneObject.IsLatestParentSet)
+                    {
+                        parentId = parentNetworkId;
+                    }
+                    networkObject.SetNetworkParenting(parentId, worldPositionStays);
+                }
+
+
+                // Dynamically spawned NetworkObjects that occur during a LoadSceneMode.Single load scene event are migrated into the DDOL
+                // until the scene is loaded. They are then migrated back into the newly loaded and currently active scene.
+                if (!sceneObject.IsSceneObject && NetworkSceneManager.IsSpawnedObjectsPendingInDontDestroyOnLoad)
+                {
+                    UnityEngine.Object.DontDestroyOnLoad(networkObject.gameObject);
+                }
+            }
+            return networkObject;
+        }
+
         // Ran on both server and client
         internal void SpawnNetworkObjectLocally(NetworkObject networkObject, ulong networkId, bool sceneObject, bool playerObject, ulong ownerClientId, bool destroyWithScene)
         {
@@ -451,8 +504,7 @@ namespace Unity.Netcode
         }
 
         // Ran on both server and client
-        internal void SpawnNetworkObjectLocally(NetworkObject networkObject, in NetworkObject.SceneObject sceneObject,
+        internal void SpawnNetworkObjectLocally(NetworkObject networkObject, in NetworkObject.SceneObject sceneObject, bool destroyWithScene)
-            FastBufferReader variableData, bool destroyWithScene)
         {
             if (networkObject == null)
             {
@@ -464,9 +516,7 @@ namespace Unity.Netcode
                 throw new SpawnStateException("Object is already spawned");
             }
 
-            networkObject.SetNetworkVariableData(variableData);
+            SpawnNetworkObjectLocallyCommon(networkObject, sceneObject.NetworkObjectId, sceneObject.IsSceneObject, sceneObject.IsPlayerObject, sceneObject.OwnerClientId, destroyWithScene);
-
-            SpawnNetworkObjectLocallyCommon(networkObject, sceneObject.Header.NetworkObjectId, sceneObject.Header.IsSceneObject, sceneObject.Header.IsPlayerObject, sceneObject.Header.OwnerClientId, destroyWithScene);
         }
 
         private void SpawnNetworkObjectLocallyCommon(NetworkObject networkObject, ulong networkId, bool sceneObject, bool playerObject, ulong ownerClientId, bool destroyWithScene)
@@ -542,7 +592,6 @@ namespace Unity.Netcode
                 }
             }
 
-            networkObject.SetCachedParent(networkObject.transform.parent);
             networkObject.ApplyNetworkParenting();
             NetworkObject.CheckOrphanChildren();
 
@@ -572,8 +621,6 @@ namespace Unity.Netcode
             };
             var size = NetworkManager.SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, clientId);
             NetworkManager.NetworkMetrics.TrackObjectSpawnSent(clientId, networkObject, size);
-
-            networkObject.MarkVariablesDirty();
         }
 
         internal ulong? GetSpawnParentId(NetworkObject networkObject)
@@ -611,7 +658,11 @@ namespace Unity.Netcode
         // Makes scene objects ready to be reused
         internal void ServerResetShudownStateForSceneObjects()
         {
+#if UNITY_2023_1_OR_NEWER
+            var networkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID).Where((c) => c.IsSceneObject != null && c.IsSceneObject == true);
+#else
             var networkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsSceneObject != null && c.IsSceneObject == true);
+#endif
             foreach (var sobj in networkObjects)
             {
                 sobj.IsSpawned = false;
@@ -642,7 +693,11 @@ namespace Unity.Netcode
 
         internal void DespawnAndDestroyNetworkObjects()
         {
+#if UNITY_2023_1_OR_NEWER
+            var networkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID);
+#else
             var networkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>();
+#endif
 
             for (int i = 0; i < networkObjects.Length; i++)
             {
@@ -672,7 +727,11 @@ namespace Unity.Netcode
 
         internal void DestroySceneObjects()
         {
+#if UNITY_2023_1_OR_NEWER
+            var networkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID);
+#else
             var networkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>();
+#endif
 
             for (int i = 0; i < networkObjects.Length; i++)
             {
@@ -699,7 +758,11 @@ namespace Unity.Netcode
 
         internal void ServerSpawnSceneObjectsOnStartSweep()
         {
+#if UNITY_2023_1_OR_NEWER
+            var networkObjects = UnityEngine.Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID);
+#else
             var networkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>();
+#endif
             var networkObjectsToSpawn = new List<NetworkObject>();
 
             for (int i = 0; i < networkObjects.Length; i++)
@@ -742,15 +805,26 @@ namespace Unity.Netcode
             }
 
             // If we are shutting down the NetworkManager, then ignore resetting the parent
-            if (!NetworkManager.ShutdownInProgress)
+            // and only attempt to remove the child's parent on the server-side
+            if (!NetworkManager.ShutdownInProgress && NetworkManager.IsServer)
             {
                 // Move child NetworkObjects to the root when parent NetworkObject is destroyed
                 foreach (var spawnedNetObj in SpawnedObjectsList)
                 {
-                    var (isReparented, latestParent) = spawnedNetObj.GetNetworkParenting();
+                    var latestParent = spawnedNetObj.GetNetworkParenting();
-                    if (isReparented && latestParent == networkObject.NetworkObjectId)
+                    if (latestParent.HasValue && latestParent.Value == networkObject.NetworkObjectId)
                     {
-                        spawnedNetObj.gameObject.transform.parent = null;
+                        // Try to remove the parent using the cached WorldPositioNStays value
+                        // Note: WorldPositionStays will still default to true if this was an
+                        // in-scene placed NetworkObject and parenting was predefined in the
+                        // scene via the editor.
+                        if (!spawnedNetObj.TryRemoveParentCachedWorldPositionStays())
+                        {
+                            if (NetworkLog.CurrentLogLevel <= LogLevel.Normal)
+                            {
+                                NetworkLog.LogError($"{nameof(NetworkObject)} #{spawnedNetObj.NetworkObjectId} could not be moved to the root when its parent {nameof(NetworkObject)} #{networkObject.NetworkObjectId} was being destroyed");
+                            }
+                        }
 
                         if (NetworkLog.CurrentLogLevel <= LogLevel.Normal)
                         {

Runtime/Timing/NetworkTickSystem.cs

@@ -3,6 +3,10 @@ using Unity.Profiling;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// Provides discretized time.
+    /// This is useful for games that require ticks happening at regular interval on the server and clients.
+    /// </summary>
     public class NetworkTickSystem
     {
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
@@ -69,6 +73,8 @@ namespace Unity.Netcode
         /// <summary>
         /// Called after advancing the time system to run ticks based on the difference in time.
         /// </summary>
+        /// <param name="localTimeSec">The local time in seconds</param>
+        /// <param name="serverTimeSec">The server time in seconds</param>
         public void UpdateTick(double localTimeSec, double serverTimeSec)
         {
             // store old local tick to know how many fixed ticks passed

Runtime/Timing/NetworkTime.cs

@@ -25,7 +25,7 @@ namespace Unity.Netcode
         public double TickOffset => m_CachedTickOffset;
 
         /// <summary>
-        /// Gets the current time. This is a non fixed time value and similar to <see cref="Time.time"/>
+        /// Gets the current time. This is a non fixed time value and similar to <see cref="Time.time"/>.
         /// </summary>
         public double Time => m_TimeSec;
 
@@ -35,13 +35,13 @@ namespace Unity.Netcode
         public float TimeAsFloat => (float)m_TimeSec;
 
         /// <summary>
-        /// Gets he current fixed network time. This is the time value of the last network tick. Similar to <see cref="Time.fixedTime"/>
+        /// Gets he current fixed network time. This is the time value of the last network tick. Similar to <see cref="Time.fixedUnscaledTime"/>.
         /// </summary>
         public double FixedTime => m_CachedTick * m_TickInterval;
 
         /// <summary>
         /// Gets the fixed delta time. This value is based on the <see cref="TickRate"/> and stays constant.
-        /// Similar to <see cref="Time.fixedDeltaTime"/> There is no equivalent to <see cref="Time.deltaTime"/>
+        /// Similar to <see cref="Time.fixedUnscaledTime"/> There is no equivalent to <see cref="Time.deltaTime"/>.
         /// </summary>
         public float FixedDeltaTime => (float)m_TickInterval;
 
@@ -108,6 +108,11 @@ namespace Unity.Netcode
             return new NetworkTime(m_TickRate, m_CachedTick);
         }
 
+        /// <summary>
+        /// Returns the time a number of ticks in the past.
+        /// </summary>
+        /// <param name="ticks">The number of ticks ago we're querying the time</param>
+        /// <returns></returns>
         public NetworkTime TimeTicksAgo(int ticks)
         {
             return this - new NetworkTime(TickRate, ticks);
@@ -132,16 +137,34 @@ namespace Unity.Netcode
             }
         }
 
+        /// <summary>
+        /// Computes the time difference between two ticks
+        /// </summary>
+        /// <param name="a">End time</param>
+        /// <param name="b">Start time</param>
+        /// <returns>The time difference between start and end</returns>
         public static NetworkTime operator -(NetworkTime a, NetworkTime b)
         {
             return new NetworkTime(a.TickRate, a.Time - b.Time);
         }
 
+        /// <summary>
+        /// Computes the sum of two times
+        /// </summary>
+        /// <param name="a">First time</param>
+        /// <param name="b">Second time</param>
+        /// <returns>The sum of the two times passed in</returns>
         public static NetworkTime operator +(NetworkTime a, NetworkTime b)
         {
             return new NetworkTime(a.TickRate, a.Time + b.Time);
         }
 
+        /// <summary>
+        /// Computes the time a number of seconds later
+        /// </summary>
+        /// <param name="a">The start time</param>
+        /// <param name="b">The number of seconds to add</param>
+        /// <returns>The resulting time</returns>
         public static NetworkTime operator +(NetworkTime a, double b)
         {
             a.m_TimeSec += b;
@@ -149,6 +172,12 @@ namespace Unity.Netcode
             return a;
         }
 
+        /// <summary>
+        /// Computes the time a number of seconds before
+        /// </summary>
+        /// <param name="a">The start time</param>
+        /// <param name="b">The number of seconds to remove</param>
+        /// <returns>The resulting time</returns>
         public static NetworkTime operator -(NetworkTime a, double b)
         {
             return a + -b;

Runtime/Timing/NetworkTimeSystem.cs

@@ -36,12 +36,27 @@ namespace Unity.Netcode
         /// Gets or sets the ratio at which the NetworkTimeSystem speeds up or slows down time.
         /// </summary>
         public double AdjustmentRatio { get; set; }
+
+        /// <summary>
+        /// The current local time with the local time offset applied
+        /// </summary>
         public double LocalTime => m_TimeSec + m_CurrentLocalTimeOffset;
+
+        /// <summary>
+        /// The current server time with the server time offset applied
+        /// </summary>
         public double ServerTime => m_TimeSec + m_CurrentServerTimeOffset;
 
         internal double LastSyncedServerTimeSec { get; private set; }
         internal double LastSyncedRttSec { get; private set; }
 
+        /// <summary>
+        /// The constructor class for <see cref="NetworkTickSystem"/>
+        /// </summary>
+        /// <param name="localBufferSec">The amount of time, in seconds, the server should buffer incoming client messages.</param>
+        /// <param name="serverBufferSec">The amount of the time in seconds the client should buffer incoming messages from the server.</param>
+        /// <param name="hardResetThresholdSec">The threshold, in seconds, used to force a hard catchup of network time.</param>
+        /// <param name="adjustmentRatio">The ratio at which the NetworkTimeSystem speeds up or slows down time.</param>
         public NetworkTimeSystem(double localBufferSec, double serverBufferSec, double hardResetThresholdSec, double adjustmentRatio = 0.01d)
         {
             LocalBufferSec = localBufferSec;
@@ -61,7 +76,7 @@ namespace Unity.Netcode
         }
 
         /// <summary>
-        /// Advances the time system by a certain amount of time. Should be called once per frame with Time.deltaTime or similar.
+        /// Advances the time system by a certain amount of time. Should be called once per frame with Time.unscaledDeltaTime or similar.
         /// </summary>
         /// <param name="deltaTimeSec">The amount of time to advance. The delta time which passed since Advance was last called.</param>
         /// <returns></returns>

Runtime/Transports/NetworkTransport.cs

@@ -3,6 +3,11 @@ using UnityEngine;
 
 namespace Unity.Netcode
 {
+    /// <summary>
+    /// The generic transport class all Netcode for GameObjects network transport implementations
+    /// derive from.  Use this class to add a custom transport.
+    /// <seealso cref="Transports.UTP.UnityTransport"> for an example of how a transport is integrated</seealso>
+    /// </summary>
     public abstract class NetworkTransport : MonoBehaviour
     {
         /// <summary>
@@ -45,7 +50,7 @@ namespace Unity.Netcode
         }
 
         /// <summary>
-        /// Send a payload to the specified clientId, data and channelName.
+        /// Send a payload to the specified clientId, data and networkDelivery.
         /// </summary>
         /// <param name="clientId">The clientId to send to</param>
         /// <param name="payload">The data to send</param>
@@ -64,11 +69,13 @@ namespace Unity.Netcode
         /// <summary>
         /// Connects client to the server
         /// </summary>
+        /// <returns>Returns success or failure</returns>
         public abstract bool StartClient();
 
         /// <summary>
         /// Starts to listening for incoming clients
         /// </summary>
+        /// <returns>Returns success or failure</returns>
         public abstract bool StartServer();
 
         /// <summary>

Runtime/Transports/UNET/UNetTransport.cs

@@ -7,6 +7,7 @@ using UnityEngine.Networking;
 
 namespace Unity.Netcode.Transports.UNET
 {
+    [AddComponentMenu("Netcode/UNet Transport")]
     public class UNetTransport : NetworkTransport
     {
         public enum SendMode

Runtime/Transports/UTP/BatchedReceiveQueue.cs

@@ -1,5 +1,9 @@
 using System;
 using Unity.Networking.Transport;
+#if UTP_TRANSPORT_2_0_ABOVE
+using Unity.Collections;
+using Unity.Collections.LowLevel.Unsafe;
+#endif
 
 namespace Unity.Netcode.Transports.UTP
 {
@@ -25,7 +29,11 @@ namespace Unity.Netcode.Transports.UTP
             {
                 fixed (byte* dataPtr = m_Data)
                 {
+#if UTP_TRANSPORT_2_0_ABOVE
+                    reader.ReadBytesUnsafe(dataPtr, reader.Length);
+#else
                     reader.ReadBytes(dataPtr, reader.Length);
+#endif
                 }
             }
 
@@ -62,7 +70,11 @@ namespace Unity.Netcode.Transports.UTP
             {
                 fixed (byte* dataPtr = m_Data)
                 {
+#if UTP_TRANSPORT_2_0_ABOVE
+                    reader.ReadBytesUnsafe(dataPtr + m_Offset + m_Length, reader.Length);
+#else
                     reader.ReadBytes(dataPtr + m_Offset + m_Length, reader.Length);
+#endif
                 }
             }
 

Runtime/Transports/UTP/BatchedSendQueue.cs

@@ -8,22 +8,30 @@ namespace Unity.Netcode.Transports.UTP
     /// <summary>Queue for batched messages meant to be sent through UTP.</summary>
     /// <remarks>
     /// Messages should be pushed on the queue with <see cref="PushMessage"/>. To send batched
-    /// messages, call <see cref="FillWriter"> with the <see cref="DataStreamWriter"/> obtained from
+    /// messages, call <see cref="FillWriterWithMessages"/> or <see cref="FillWriterWithBytes"/>
-    /// <see cref="NetworkDriver.BeginSend"/>. This will fill the writer with as many messages as
+    /// with the <see cref="DataStreamWriter"/> obtained from <see cref="NetworkDriver.BeginSend"/>.
-    /// possible. If the send is successful, call <see cref="Consume"/> to remove the data from the
+    /// This will fill the writer with as many messages/bytes as possible. If the send is
-    /// queue.
+    /// successful, call <see cref="Consume"/> to remove the data from the queue.
     ///
     /// This is meant as a companion to <see cref="BatchedReceiveQueue"/>, which should be used to
     /// read messages sent with this queue.
     /// </remarks>
     internal struct BatchedSendQueue : IDisposable
     {
-        private NativeArray<byte> m_Data;
+        // Note that we're using NativeList basically like a growable NativeArray, where the length
+        // of the list is the capacity of our array. (We can't use the capacity of the list as our
+        // queue capacity because NativeList may elect to set it higher than what we'd set it to
+        // with SetCapacity, which breaks the logic of our code.)
+        private NativeList<byte> m_Data;
         private NativeArray<int> m_HeadTailIndices;
+        private int m_MaximumCapacity;
+        private int m_MinimumCapacity;
 
         /// <summary>Overhead that is added to each message in the queue.</summary>
         public const int PerMessageOverhead = sizeof(int);
 
+        internal const int MinimumMinimumCapacity = 4096;
+
         // Indices into m_HeadTailIndicies.
         private const int k_HeadInternalIndex = 0;
         private const int k_TailInternalIndex = 1;
@@ -43,18 +51,33 @@ namespace Unity.Netcode.Transports.UTP
         }
 
         public int Length => TailIndex - HeadIndex;
-
+        public int Capacity => m_Data.Length;
         public bool IsEmpty => HeadIndex == TailIndex;
-
         public bool IsCreated => m_Data.IsCreated;
 
         /// <summary>Construct a new empty send queue.</summary>
         /// <param name="capacity">Maximum capacity of the send queue.</param>
         public BatchedSendQueue(int capacity)
         {
-            m_Data = new NativeArray<byte>(capacity, Allocator.Persistent);
+            // Make sure the maximum capacity will be even.
+            m_MaximumCapacity = capacity + (capacity & 1);
+
+            // We pick the minimum capacity such that if we keep doubling it, we'll eventually hit
+            // the maximum capacity exactly. The alternative would be to use capacities that are
+            // powers of 2, but this can lead to over-allocating quite a bit of memory (especially
+            // since we expect maximum capacities to be in the megabytes range). The approach taken
+            // here avoids this issue, at the cost of not having allocations of nice round sizes.
+            m_MinimumCapacity = m_MaximumCapacity;
+            while (m_MinimumCapacity / 2 >= MinimumMinimumCapacity)
+            {
+                m_MinimumCapacity /= 2;
+            }
+
+            m_Data = new NativeList<byte>(m_MinimumCapacity, Allocator.Persistent);
             m_HeadTailIndices = new NativeArray<int>(2, Allocator.Persistent);
 
+            m_Data.ResizeUninitialized(m_MinimumCapacity);
+
             HeadIndex = 0;
             TailIndex = 0;
         }
@@ -68,18 +91,28 @@ namespace Unity.Netcode.Transports.UTP
             }
         }
 
+        /// <summary>Write a raw buffer to a DataStreamWriter.</summary>
+        private unsafe void WriteBytes(ref DataStreamWriter writer, byte* data, int length)
+        {
+#if UTP_TRANSPORT_2_0_ABOVE
+            writer.WriteBytesUnsafe(data, length);
+#else
+            writer.WriteBytes(data, length);
+#endif
+        }
+
         /// <summary>Append data at the tail of the queue. No safety checks.</summary>
         private void AppendDataAtTail(ArraySegment<byte> data)
         {
             unsafe
             {
-                var writer = new DataStreamWriter((byte*)m_Data.GetUnsafePtr() + TailIndex, m_Data.Length - TailIndex);
+                var writer = new DataStreamWriter((byte*)m_Data.GetUnsafePtr() + TailIndex, Capacity - TailIndex);
 
                 writer.WriteInt(data.Count);
 
                 fixed (byte* dataPtr = data.Array)
                 {
-                    writer.WriteBytes(dataPtr + data.Offset, data.Count);
+                    WriteBytes(ref writer, dataPtr + data.Offset, data.Count);
                 }
             }
 
@@ -100,16 +133,16 @@ namespace Unity.Netcode.Transports.UTP
             }
 
             // Check if there's enough room after the current tail index.
-            if (m_Data.Length - TailIndex >= sizeof(int) + message.Count)
+            if (Capacity - TailIndex >= sizeof(int) + message.Count)
             {
                 AppendDataAtTail(message);
                 return true;
             }
 
-            // Check if there would be enough room if we moved data at the beginning of m_Data.
+            // Move the data at the beginning of of m_Data. Either it will leave enough space for
-            if (m_Data.Length - TailIndex + HeadIndex >= sizeof(int) + message.Count)
+            // the message, or we'll grow m_Data and will want the data at the beginning anyway.
+            if (HeadIndex > 0 && Length > 0)
             {
-                // Move the data back at the beginning of m_Data.
                 unsafe
                 {
                     UnsafeUtility.MemMove(m_Data.GetUnsafePtr(), (byte*)m_Data.GetUnsafePtr() + HeadIndex, Length);
@@ -117,14 +150,40 @@ namespace Unity.Netcode.Transports.UTP
 
                 TailIndex = Length;
                 HeadIndex = 0;
+            }
 
+            // If there's enough space left at the end for the message, now is a good time to trim
+            // the capacity of m_Data if it got very large. We define "very large" here as having
+            // more than 75% of m_Data unused after adding the new message.
+            if (Capacity - TailIndex >= sizeof(int) + message.Count)
+            {
                 AppendDataAtTail(message);
+
+                while (TailIndex < Capacity / 4 && Capacity > m_MinimumCapacity)
+                {
+                    m_Data.ResizeUninitialized(Capacity / 2);
+                }
+
                 return true;
             }
 
+            // If we get here we need to grow m_Data until the data fits (or it's too large).
+            while (Capacity - TailIndex < sizeof(int) + message.Count)
+            {
+                // Can't grow m_Data anymore. Message simply won't fit.
+                if (Capacity * 2 > m_MaximumCapacity)
+                {
                     return false;
                 }
 
+                m_Data.ResizeUninitialized(Capacity * 2);
+            }
+
+            // If we get here we know there's now enough room for the message.
+            AppendDataAtTail(message);
+            return true;
+        }
+
         /// <summary>
         /// Fill as much of a <see cref="DataStreamWriter"/> as possible with data from the head of
         /// the queue. Only full messages (and their length) are written to the writer.
@@ -149,12 +208,12 @@ namespace Unity.Netcode.Transports.UTP
 
             unsafe
             {
-                var reader = new DataStreamReader((byte*)m_Data.GetUnsafePtr() + HeadIndex, Length);
+                var reader = new DataStreamReader(m_Data.AsArray());
 
                 var writerAvailable = writer.Capacity;
-                var readerOffset = 0;
+                var readerOffset = HeadIndex;
 
-                while (readerOffset < Length)
+                while (readerOffset < TailIndex)
                 {
                     reader.SeekSet(readerOffset);
                     var messageLength = reader.ReadInt();
@@ -168,7 +227,7 @@ namespace Unity.Netcode.Transports.UTP
                         writer.WriteInt(messageLength);
 
                         var messageOffset = HeadIndex + reader.GetBytesRead();
-                        writer.WriteBytes((byte*)m_Data.GetUnsafePtr() + messageOffset, messageLength);
+                        WriteBytes(ref writer, (byte*)m_Data.GetUnsafePtr() + messageOffset, messageLength);
 
                         writerAvailable -= sizeof(int) + messageLength;
                         readerOffset += sizeof(int) + messageLength;
@@ -205,7 +264,7 @@ namespace Unity.Netcode.Transports.UTP
 
             unsafe
             {
-                writer.WriteBytes((byte*)m_Data.GetUnsafePtr() + HeadIndex, copyLength);
+                WriteBytes(ref writer, (byte*)m_Data.GetUnsafePtr() + HeadIndex, copyLength);
             }
 
             return copyLength;
@@ -219,10 +278,14 @@ namespace Unity.Netcode.Transports.UTP
         /// <param name="size">Number of bytes to consume from the queue.</param>
         public void Consume(int size)
         {
+            // Adjust the head/tail indices such that we consume the given size.
             if (size >= Length)
             {
                 HeadIndex = 0;
                 TailIndex = 0;
+
+                // This is a no-op if m_Data is already at minimum capacity.
+                m_Data.ResizeUninitialized(m_MinimumCapacity);
             }
             else
             {

Runtime/Transports/UTP/NetworkMetricsContext.cs

@@ -1,8 +1,17 @@
 namespace Unity.Netcode.Transports.UTP
 {
+    /// <summary>
+    /// Caching structure to track network metrics related information.
+    /// </summary>
     public struct NetworkMetricsContext
     {
+        /// <summary>
+        /// The number of packet sent.
+        /// </summary>
         public uint PacketSentCount;
+        /// <summary>
+        /// The number of packet received.
+        /// </summary>
         public uint PacketReceivedCount;
     }
 }

Runtime/Transports/UTP/NetworkMetricsPipelineStage.cs

@@ -4,25 +4,24 @@ using AOT;
 using Unity.Burst;
 using Unity.Collections.LowLevel.Unsafe;
 using Unity.Networking.Transport;
-using UnityEngine;
 
 namespace Unity.Netcode.Transports.UTP
 {
     [BurstCompile]
     internal unsafe struct NetworkMetricsPipelineStage : INetworkPipelineStage
     {
-        static TransportFunctionPointer<NetworkPipelineStage.ReceiveDelegate> ReceiveFunction = new TransportFunctionPointer<NetworkPipelineStage.ReceiveDelegate>(Receive);
+        private static TransportFunctionPointer<NetworkPipelineStage.ReceiveDelegate> s_ReceiveFunction = new TransportFunctionPointer<NetworkPipelineStage.ReceiveDelegate>(Receive);
-        static TransportFunctionPointer<NetworkPipelineStage.SendDelegate> SendFunction = new TransportFunctionPointer<NetworkPipelineStage.SendDelegate>(Send);
+        private static TransportFunctionPointer<NetworkPipelineStage.SendDelegate> s_SendFunction = new TransportFunctionPointer<NetworkPipelineStage.SendDelegate>(Send);
-        static TransportFunctionPointer<NetworkPipelineStage.InitializeConnectionDelegate> InitializeConnectionFunction = new TransportFunctionPointer<NetworkPipelineStage.InitializeConnectionDelegate>(InitializeConnection);
+        private static TransportFunctionPointer<NetworkPipelineStage.InitializeConnectionDelegate> s_InitializeConnectionFunction = new TransportFunctionPointer<NetworkPipelineStage.InitializeConnectionDelegate>(InitializeConnection);
 
         public NetworkPipelineStage StaticInitialize(byte* staticInstanceBuffer,
             int staticInstanceBufferLength,
             NetworkSettings settings)
         {
             return new NetworkPipelineStage(
-                ReceiveFunction,
+                s_ReceiveFunction,
-                SendFunction,
+                s_SendFunction,
-                InitializeConnectionFunction,
+                s_InitializeConnectionFunction,
                 ReceiveCapacity: 0,
                 SendCapacity: 0,
                 HeaderCapacity: 0,

Runtime/Transports/UTP/SecretsLoaderHelper.cs

@@ -0,0 +1,188 @@
+using System;
+using System.IO;
+using UnityEngine;
+
+namespace Unity.Netcode.Transports.UTP
+{
+    /// <summary>
+    /// Component to add to a NetworkManager if you want the certificates to be loaded from files.
+    /// Mostly helpful to ease development and testing, especially with self-signed certificates
+    ///
+    /// Shipping code should make the calls to
+    /// - SetServerSecrets
+    /// - SetClientSecrets
+    /// directly, instead of relying on this.
+    /// </summary>
+    public class SecretsLoaderHelper : MonoBehaviour
+    {
+        internal struct ServerSecrets
+        {
+            public string ServerPrivate;
+            public string ServerCertificate;
+        };
+
+        internal struct ClientSecrets
+        {
+            public string ServerCommonName;
+            public string ClientCertificate;
+        };
+
+        private void Awake()
+        {
+            var serverSecrets = new ServerSecrets();
+
+            try
+            {
+                serverSecrets.ServerCertificate = ServerCertificate;
+            }
+            catch (Exception exception)
+            {
+                Debug.Log(exception);
+            }
+
+            try
+            {
+                serverSecrets.ServerPrivate = ServerPrivate;
+            }
+            catch (Exception exception)
+            {
+                Debug.Log(exception);
+            }
+
+            var clientSecrets = new ClientSecrets();
+            try
+            {
+                clientSecrets.ClientCertificate = ClientCA;
+            }
+            catch (Exception exception)
+            {
+                Debug.Log(exception);
+            }
+
+            try
+            {
+                clientSecrets.ServerCommonName = ServerCommonName;
+            }
+            catch (Exception exception)
+            {
+                Debug.Log(exception);
+            }
+
+            var unityTransportComponent = GetComponent<UnityTransport>();
+
+            if (unityTransportComponent == null)
+            {
+                Debug.LogError($"You need to select the UnityTransport protocol, in the NetworkManager, in order for the SecretsLoaderHelper component to be useful.");
+                return;
+            }
+
+            unityTransportComponent.SetServerSecrets(serverSecrets.ServerCertificate, serverSecrets.ServerPrivate);
+            unityTransportComponent.SetClientSecrets(clientSecrets.ServerCommonName, clientSecrets.ClientCertificate);
+        }
+
+        [Tooltip("Hostname")]
+        [SerializeField]
+        private string m_ServerCommonName = "localhost";
+
+        /// <summary>Common name of the server (typically its hostname).</summary>
+        public string ServerCommonName
+        {
+            get => m_ServerCommonName;
+            set => m_ServerCommonName = value;
+        }
+
+        [Tooltip("Client CA filepath. Useful with self-signed certificates")]
+        [SerializeField]
+        private string m_ClientCAFilePath = ""; // "Assets/Secure/myGameClientCA.pem"
+
+        /// <summary>Client CA filepath. Useful with self-signed certificates</summary>
+        public string ClientCAFilePath
+        {
+            get => m_ClientCAFilePath;
+            set => m_ClientCAFilePath = value;
+        }
+
+        [Tooltip("Client CA Override. Only useful for development with self-signed certificates. Certificate content, for platforms that lack file access (WebGL)")]
+        [SerializeField]
+        private string m_ClientCAOverride = "";
+
+        /// <summary>
+        /// Client CA Override. Only useful for development with self-signed certificates.
+        /// Certificate content, for platforms that lack file access (WebGL)
+        /// </summary>
+        public string ClientCAOverride
+        {
+            get => m_ClientCAOverride;
+            set => m_ClientCAOverride = value;
+        }
+
+        [Tooltip("Server Certificate filepath")]
+        [SerializeField]
+        private string m_ServerCertificateFilePath = ""; // "Assets/Secure/myGameServerCertificate.pem"
+
+        /// <summary>Server Certificate filepath</summary>
+        public string ServerCertificateFilePath
+        {
+            get => m_ServerCertificateFilePath;
+            set => m_ServerCertificateFilePath = value;
+        }
+
+        [Tooltip("Server Private Key filepath")]
+        [SerializeField]
+        private string m_ServerPrivateFilePath = ""; // "Assets/Secure/myGameServerPrivate.pem"
+
+        /// <summary>Server Private Key filepath</summary>
+        public string ServerPrivateFilePath
+        {
+            get => m_ServerPrivateFilePath;
+            set => m_ServerPrivate = value;
+        }
+
+        private string m_ClientCA;
+
+        /// <summary>CA certificate used by the client.</summary>
+        public string ClientCA
+        {
+            get
+            {
+                if (m_ClientCAOverride != "")
+                {
+                    return m_ClientCAOverride;
+                }
+                return ReadFile(m_ClientCAFilePath, "Client Certificate");
+            }
+            set => m_ClientCA = value;
+        }
+
+        private string m_ServerCertificate;
+
+        /// <summary>Certificate used by the server.</summary>
+        public string ServerCertificate
+        {
+            get => ReadFile(m_ServerCertificateFilePath, "Server Certificate");
+            set => m_ServerCertificate = value;
+        }
+
+        private string m_ServerPrivate;
+
+        /// <summary>Private key used by the server.</summary>
+        public string ServerPrivate
+        {
+            get => ReadFile(m_ServerPrivateFilePath, "Server Key");
+            set => m_ServerPrivate = value;
+        }
+
+        private static string ReadFile(string path, string label)
+        {
+            if (path == null || path == "")
+            {
+                return "";
+            }
+
+            var reader = new StreamReader(path);
+            string fileContent = reader.ReadToEnd();
+            Debug.Log((fileContent.Length > 1) ? ("Successfully loaded " + fileContent.Length + " byte(s) from " + label) : ("Could not read " + label + " file"));
+            return fileContent;
+        }
+    }
+}

Runtime/Transports/UTP/SecretsLoaderHelper.cs.meta

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