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

@@ -1,4 +1,3 @@
-
 # Changelog
 
 All notable changes to this project will be documented in this file.
@@ -7,6 +6,96 @@ 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
@@ -14,7 +103,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - 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)
-- Preformance improvements for cases with large number of NetworkObjects, by not iterating over all unchanged NetworkObjects 
+- Performance improvements for cases with large number of NetworkObjects, by not iterating over all unchanged NetworkObjects
 
 ### Fixed
 
@@ -98,6 +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)
@@ -151,10 +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)
@@ -206,6 +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)
@@ -220,6 +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)
@@ -231,7 +325,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 - ResetTrigger function to NetworkAnimator (#1327)
 
-### Fixed 
+### Fixed
 
 - Overflow exception when syncing Animator state. (#1327)
 - Added `try`/`catch` around RPC calls, preventing exception from causing further RPC calls to fail (#1329)
@@ -256,7 +350,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Added `ClientNetworkTransform` sample to the SDK package (#1168)
 - Added `Bootstrap` sample to the SDK package (#1140)
 - Enhanced `NetworkSceneManager` implementation with additive scene loading capabilities (#1080, #955, #913)
-  - `NetworkSceneManager.OnSceneEvent` provides improved scene event notificaitons  
+  - `NetworkSceneManager.OnSceneEvent` provides improved scene event notificaitons
 - Enhanced `NetworkTransform` implementation with per axis/component based and threshold based state replication (#1042, #1055, #1061, #1084, #1101)
 - Added a jitter-resistent `BufferedLinearInterpolator<T>` for `NetworkTransform` (#1060)
 - Implemented `NetworkPrefabHandler` that provides support for object pooling and `NetworkPrefab` overrides (#1073, #1004, #977, #905,#749, #727)
@@ -313,7 +407,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Removed `NetworkDictionary`, `NetworkSet` (#1149)
 - Removed `NetworkVariableSettings` (#1097)
 - Removed predefined `NetworkVariable<T>` types (#1093)
-    - Removed `NetworkVariableBool`, `NetworkVariableByte`, `NetworkVariableSByte`, `NetworkVariableUShort`, `NetworkVariableShort`, `NetworkVariableUInt`, `NetworkVariableInt`, `NetworkVariableULong`, `NetworkVariableLong`, `NetworkVariableFloat`, `NetworkVariableDouble`, `NetworkVariableVector2`, `NetworkVariableVector3`, `NetworkVariableVector4`, `NetworkVariableColor`, `NetworkVariableColor32`, `NetworkVariableRay`, `NetworkVariableQuaternion`
+  - Removed `NetworkVariableBool`, `NetworkVariableByte`, `NetworkVariableSByte`, `NetworkVariableUShort`, `NetworkVariableShort`, `NetworkVariableUInt`, `NetworkVariableInt`, `NetworkVariableULong`, `NetworkVariableLong`, `NetworkVariableFloat`, `NetworkVariableDouble`, `NetworkVariableVector2`, `NetworkVariableVector3`, `NetworkVariableVector4`, `NetworkVariableColor`, `NetworkVariableColor32`, `NetworkVariableRay`, `NetworkVariableQuaternion`
 - Removed `NetworkChannel` and `MultiplexTransportAdapter` (#1133)
 - Removed ILPP backend for 2019.4, minimum required version is 2020.3+ (#895)
 - `NetworkManager.NetworkConfig` had the following properties removed: (#1080)
@@ -385,14 +479,14 @@ This is the initial experimental Unity MLAPI Package, v0.1.0.
 - Integrated MLAPI with the Unity Profiler for versions 2020.2 and later:
   - Added new profiler modules for MLAPI that report important network data.
   - Attached the profiler to a remote player to view network data over the wire.
-- A test project is available for building and experimenting with MLAPI features. This project is available in the MLAPI GitHub [testproject folder](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/tree/release/0.1.0/testproject). 
+- A test project is available for building and experimenting with MLAPI features. This project is available in the MLAPI GitHub [testproject folder](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/tree/release/0.1.0/testproject).
 - Added a [MLAPI Community Contributions](https://github.com/Unity-Technologies/mlapi-community-contributions/tree/master/com.mlapi.contrib.extensions) new GitHub repository to accept extensions from the MLAPI community. Current extensions include moved MLAPI features for lag compensation (useful for Server Authoritative actions) and `TrackedObject`.
 
 ### Changed
 
 - [GitHub 520](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/520): MLAPI now uses the Unity Package Manager for installation management.
-- Added functionality and usability to `NetworkVariable`, previously called `NetworkVar`. Updates enhance options and fully replace the need for `SyncedVar`s. 
-- [GitHub 507](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/507): Reimplemented `NetworkAnimator`, which synchronizes animation states for networked objects. 
+- Added functionality and usability to `NetworkVariable`, previously called `NetworkVar`. Updates enhance options and fully replace the need for `SyncedVar`s.
+- [GitHub 507](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/507): Reimplemented `NetworkAnimator`, which synchronizes animation states for networked objects.
 - GitHub [444](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/444) and [455](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/455): Channels are now represented as bytes instead of strings.
 
 For users of previous versions of MLAPI, this release renames APIs due to refactoring. All obsolete marked APIs have been removed as per [GitHub 513](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/513) and [GitHub 514](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/514).
@@ -425,7 +519,7 @@ For users of previous versions of MLAPI, this release renames APIs due to refact
 
 ### Fixed
 
-- [GitHub 460](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/460): Fixed an issue for RPC where the host-server was not receiving RPCs from the host-client and vice versa without the loopback flag set in `NetworkingManager`. 
+- [GitHub 460](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/460): Fixed an issue for RPC where the host-server was not receiving RPCs from the host-client and vice versa without the loopback flag set in `NetworkingManager`.
 - Fixed an issue where data in the Profiler was incorrectly aggregated and drawn, which caused the profiler data to increment indefinitely instead of resetting each frame.
 - Fixed an issue the client soft-synced causing PlayMode client-only scene transition issues, caused when running the client in the editor and the host as a release build. Users may have encountered a soft sync of `NetworkedInstanceId` issues in the `SpawnManager.ClientCollectSoftSyncSceneObjectSweep` method.
 - [GitHub 458](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/458): Fixed serialization issues in `NetworkList` and `NetworkDictionary` when running in Server mode.
@@ -440,10 +534,10 @@ With a new release of MLAPI in Unity, some features have been removed:
 - SyncVars have been removed from MLAPI. Use `NetworkVariable`s in place of this functionality. <!-- MTT54 -->
 - [GitHub 527](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/527): Lag compensation systems and `TrackedObject` have moved to the new [MLAPI Community Contributions](https://github.com/Unity-Technologies/mlapi-community-contributions/tree/master/com.mlapi.contrib.extensions) repo.
 - [GitHub 509](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/509): Encryption has been removed from MLAPI. The `Encryption` option in `NetworkConfig` on the `NetworkingManager` is not available in this release. This change will not block game creation or running. A current replacement for this functionality is not available, and may be developed in future releases. See the following changes:
-    - Removed `SecuritySendFlags` from all APIs.
-    - Removed encryption, cryptography, and certificate configurations from APIs including `NetworkManager` and `NetworkConfig`.
-    - Removed "hail handshake", including `NetworkManager` implementation and `NetworkConstants` entries.
-    - Modified `RpcQueue` and `RpcBatcher` internals to remove encryption and authentication from reading and writing.
+  - Removed `SecuritySendFlags` from all APIs.
+  - Removed encryption, cryptography, and certificate configurations from APIs including `NetworkManager` and `NetworkConfig`.
+  - Removed "hail handshake", including `NetworkManager` implementation and `NetworkConstants` entries.
+  - Modified `RpcQueue` and `RpcBatcher` internals to remove encryption and authentication from reading and writing.
 - Removed the previous MLAPI Profiler editor window from Unity versions 2020.2 and later.
 - Removed previous MLAPI Convenience and Performance RPC APIs with the new standard RPC API. See [RFC #1](https://github.com/Unity-Technologies/com.unity.multiplayer.rfcs/blob/master/text/0001-std-rpc-api.md) for details.
 - [GitHub 520](https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/pull/520): Removed the MLAPI Installer.
@@ -456,7 +550,7 @@ With a new release of MLAPI in Unity, some features have been removed:
 - For `NetworkVariable`, the `NetworkDictionary` `List` and `Set` must use the `reliableSequenced` channel.
 - `NetworkObjects`s are supported but when spawning a prefab with nested child network objects you have to manually call spawn on them
 - `NetworkTransform` have the following issues:
-  - Replicated objects may have jitter. 
+  - Replicated objects may have jitter.
   - The owner is always authoritative about the object's position.
   - Scale is not synchronized.
 - Connection Approval is not called on the host client.

Components/Interpolator/BufferedLinearInterpolator.cs

@@ -248,6 +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);
@@ -292,7 +294,9 @@ namespace Unity.Netcode
         /// <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 />
@@ -311,13 +315,17 @@ namespace Unity.Netcode
         /// <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
@@ -32,7 +37,14 @@ namespace Unity.Netcode.Components
 
             foreach (var sendEntry in m_SendTriggerUpdates)
             {
-                m_NetworkAnimator.SendAnimTriggerClientRpc(sendEntry.AnimationTriggerMessage, sendEntry.ClientRpcParams);
+                if (!sendEntry.SendToServer)
+                {
+                    m_NetworkAnimator.SendAnimTriggerClientRpc(sendEntry.AnimationTriggerMessage, sendEntry.ClientRpcParams);
+                }
+                else
+                {
+                    m_NetworkAnimator.SendAnimTriggerServerRpc(sendEntry.AnimationTriggerMessage);
+                }
             }
             m_SendTriggerUpdates.Clear();
         }
@@ -44,8 +56,8 @@ namespace Unity.Netcode.Components
             {
                 case NetworkUpdateStage.PreUpdate:
                     {
-                        // Only the server forwards messages and synchronizes players
-                        if (m_NetworkAnimator.NetworkManager.IsServer)
+                        // Only the owner or the server send messages
+                        if (m_NetworkAnimator.IsOwner || m_IsServer)
                         {
                             // Flush any pending messages
                             FlushMessages();
@@ -125,6 +137,7 @@ namespace Unity.Netcode.Components
 
         private struct TriggerUpdate
         {
+            public bool SendToServer;
             public ClientRpcParams ClientRpcParams;
             public NetworkAnimator.AnimationTriggerMessage AnimationTriggerMessage;
         }
@@ -134,11 +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);
@@ -147,34 +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
-            internal bool Transition;
+            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);
-                serializer.SerializeValue(ref NormalizedTime);
-                serializer.SerializeValue(ref Layer);
-                serializer.SerializeValue(ref Weight);
+                if (serializer.IsWriter)
+                {
+                    var writer = serializer.GetFastBufferWriter();
+                    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);
+                    }
+                }
             }
         }
 
@@ -223,7 +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;
@@ -269,9 +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)
@@ -293,40 +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)
             {
-                int layers = m_Animator.layerCount;
-                m_TransitionHash = new int[layers];
-                m_AnimationHash = new int[layers];
-                m_LayerWeights = new float[layers];
+                m_ClientSendList = new List<ulong>(128);
+                m_ClientRpcParams = new ClientRpcParams();
+                m_ClientRpcParams.Send = new ClientRpcSendParams();
+                m_ClientRpcParams.Send.TargetClientIds = m_ClientSendList;
 
-                if (IsServer)
-                {
-                    NetworkManager.OnClientConnectedCallback += OnClientConnectedCallback;
-                }
+                // 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
-                for (int layer = 0; layer < m_Animator.layerCount; layer++)
+            // 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])
                 {
-                    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;
+                    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);
@@ -373,6 +655,7 @@ namespace Unity.Netcode.Components
             m_NetworkAnimatorStateChangeHandler = new NetworkAnimatorStateChangeHandler(this);
         }
 
+        /// <inheritdoc/>
         public override void OnNetworkDespawn()
         {
             Cleanup();
@@ -393,18 +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 adjustedNormalizedMaxTime = totalSpeed > 0.0f ? 1.0f / totalSpeed : 0.0f;
-                // NOTE:
-                // When synchronizing, for now we will just complete the transition and
-                // synchronize the player to the next state being transitioned into
-                if (m_Animator.IsInTransition(layer))
+                var isInTransition = m_Animator.IsInTransition(layer);
+
+                // Grab one of the available AnimationState entries so we can fill it with the current
+                // layer's animation state.
+                var animationState = m_AnimationMessage.AnimationStates[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);
@@ -422,23 +712,39 @@ namespace Unity.Netcode.Components
                     {
                         normalizedTime = 0.0f;
                     }
-
                     stateHash = nextState.fullPathHash;
+
+                    // 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))
+                    {
+                        if (m_DestinationStateToTransitioninfo[layer].ContainsKey(nextState.shortNameHash))
+                        {
+                            var destinationInfo = m_DestinationStateToTransitioninfo[layer][nextState.shortNameHash];
+                            stateHash = destinationInfo.OriginatingState;
+                            // Set the destination state to cross fade to from the originating state
+                            animationState.DestinationStateHash = destinationInfo.DestinationState;
+                        }
+                    }
                 }
 
-                var animMsg = new AnimationMessage
-                {
-                    Transition = m_Animator.IsInTransition(layer),
-                    StateHash = stateHash,
-                    NormalizedTime = normalizedTime,
-                    Layer = layer,
-                    Weight = m_LayerWeights[layer]
-                };
-                // Server always send via client RPC
-                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);
@@ -461,46 +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
-                {
-                    Transition = m_Animator.IsInTransition(layer),
-                    StateHash = stateHash,
-                    NormalizedTime = normalizedTime,
-                    Layer = layer,
-                    Weight = m_LayerWeights[layer]
-                };
+                // 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
+                // current layer's state.
+                var animationState = m_AnimationMessage.AnimationStates[m_AnimationMessage.IsDirtyCount];
 
+                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);
                 }
             }
         }
@@ -596,7 +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;
@@ -746,9 +1063,9 @@ 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)
             {
@@ -756,9 +1073,46 @@ namespace Unity.Netcode.Components
             }
 
             var currentState = m_Animator.GetCurrentAnimatorStateInfo(animationState.Layer);
-            if (currentState.fullPathHash != animationState.StateHash || m_Animator.IsInTransition(animationState.Layer) != animationState.Transition)
+            // If it is a transition, then we are synchronizing transitions in progress when a client late joins
+            if (animationState.Transition)
             {
-                m_Animator.Play(animationState.StateHash, animationState.Layer, animationState.NormalizedTime);
+                // 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);
         }
@@ -781,7 +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);
@@ -811,11 +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
             {
@@ -823,15 +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);
                 }
             }
         }
@@ -840,16 +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)
         {
-            if (IsServer)
+            // 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);
+                }
             }
         }
 
@@ -858,44 +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)
         {
-            m_Animator.SetBool(animationTriggerMessage.Hash, animationTriggerMessage.IsTriggerSet);
+            InternalSetTrigger(animationTriggerMessage.Hash, animationTriggerMessage.IsTriggerSet);
         }
 
         /// <summary>
@@ -923,14 +1315,20 @@ namespace Unity.Netcode.Components
                 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())
                     {
-                        m_Animator.SetTrigger(hash);
+                        InternalSetTrigger(hash);
                     }
                 }
             }

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;

Components/NetworkTransform.cs

@@ -10,7 +10,7 @@ namespace Unity.Netcode.Components
     /// The replicated value will be automatically be interpolated (if active) and applied to the underlying GameObject's transform.
     /// </summary>
     [DisallowMultipleComponent]
-    [AddComponentMenu("Netcode/" + nameof(NetworkTransform))]
+    [AddComponentMenu("Netcode/Network Transform")]
     [DefaultExecutionOrder(100000)] // this is needed to catch the update time after the transform was updated by user scripts
     public class NetworkTransform : NetworkBehaviour
     {
@@ -207,8 +207,13 @@ namespace Unity.Netcode.Components
             internal float ScaleX, ScaleY, ScaleZ;
             internal double SentTime;
 
+            // Authoritative and non-authoritative sides use this to determine if a NetworkTransformState is
+            // dirty or not.
             internal bool IsDirty;
 
+            // Non-Authoritative side uses this for ending extrapolation of the last applied state
+            internal int EndExtrapolationTick;
+
             /// <summary>
             /// This will reset the NetworkTransform BitSet
             /// </summary>
@@ -277,14 +282,7 @@ namespace Unity.Netcode.Components
                 {
                     // Go ahead and mark the local state dirty or not dirty as well
                     /// <see cref="TryCommitTransformToServer"/>
-                    if (HasPositionChange || HasRotAngleChange || HasScaleChange)
-                    {
-                        IsDirty = true;
-                    }
-                    else
-                    {
-                        IsDirty = false;
-                    }
+                    IsDirty = HasPositionChange || HasRotAngleChange || HasScaleChange;
                 }
             }
         }
@@ -301,6 +299,15 @@ namespace Unity.Netcode.Components
         /// Whether or not z component of position will be replicated
         /// </summary>
         public bool SyncPositionZ = true;
+
+        private bool SynchronizePosition
+        {
+            get
+            {
+                return SyncPositionX || SyncPositionY || SyncPositionZ;
+            }
+        }
+
         /// <summary>
         /// Whether or not x component of rotation will be replicated
         /// </summary>
@@ -313,6 +320,15 @@ namespace Unity.Netcode.Components
         /// Whether or not z component of rotation will be replicated
         /// </summary>
         public bool SyncRotAngleZ = true;
+
+        private bool SynchronizeRotation
+        {
+            get
+            {
+                return SyncRotAngleX || SyncRotAngleY || SyncRotAngleZ;
+            }
+        }
+
         /// <summary>
         /// Whether or not x component of scale will be replicated
         /// </summary>
@@ -326,6 +342,15 @@ namespace Unity.Netcode.Components
         /// </summary>
         public bool SyncScaleZ = true;
 
+
+        private bool SynchronizeScale
+        {
+            get
+            {
+                return SyncScaleX || SyncScaleY || SyncScaleZ;
+            }
+        }
+
         /// <summary>
         /// The current position threshold value
         /// Any changes to the position that exceeds the current threshold value will be replicated
@@ -347,7 +372,6 @@ namespace Unity.Netcode.Components
         /// </summary>
         public float ScaleThreshold = ScaleThresholdDefault;
 
-
         /// <summary>
         /// Sets whether the transform should be treated as local (true) or world (false) space.
         /// </summary>
@@ -390,7 +414,6 @@ namespace Unity.Netcode.Components
         private readonly NetworkVariable<NetworkTransformState> m_ReplicatedNetworkStateServer = new NetworkVariable<NetworkTransformState>(new NetworkTransformState(), NetworkVariableReadPermission.Everyone, NetworkVariableWritePermission.Server);
         private readonly NetworkVariable<NetworkTransformState> m_ReplicatedNetworkStateOwner = new NetworkVariable<NetworkTransformState>(new NetworkTransformState(), NetworkVariableReadPermission.Everyone, NetworkVariableWritePermission.Owner);
 
-
         internal NetworkVariable<NetworkTransformState> ReplicatedNetworkState
         {
             get
@@ -404,10 +427,10 @@ namespace Unity.Netcode.Components
             }
         }
 
+        // Used by both authoritative and non-authoritative instances.
+        // This represents the most recent local authoritative state.
         private NetworkTransformState m_LocalAuthoritativeNetworkState;
 
-        private bool m_HasSentLastValue = false; // used to send one last value, so clients can make the difference between lost replication data (clients extrapolate) and no more data to send.
-
         private ClientRpcParams m_ClientRpcParams = new ClientRpcParams() { Send = new ClientRpcSendParams() };
         private List<ulong> m_ClientIds = new List<ulong>() { 0 };
 
@@ -420,7 +443,7 @@ namespace Unity.Netcode.Components
         private BufferedLinearInterpolator<float> m_ScaleZInterpolator;
         private readonly List<BufferedLinearInterpolator<float>> m_AllFloatInterpolators = new List<BufferedLinearInterpolator<float>>(6);
 
-        private int m_LastSentTick;
+        // Used by integration test
         private NetworkTransformState m_LastSentState;
 
         internal NetworkTransformState GetLastSentState()
@@ -428,6 +451,33 @@ namespace Unity.Netcode.Components
             return m_LastSentState;
         }
 
+        /// <summary>
+        /// This is invoked when a new client joins (server and client sides)
+        /// Server Side: Serializes as if we were teleporting (everything is sent via NetworkTransformState)
+        /// Client Side: Adds the interpolated state which applies the NetworkTransformState as well
+        /// </summary>
+        protected override void OnSynchronize<T>(ref BufferSerializer<T> serializer)
+        {
+            // We don't need to synchronize NetworkTransforms that are on the same
+            // GameObject as the NetworkObject.
+            if (NetworkObject.gameObject == gameObject)
+            {
+                return;
+            }
+            var synchronizationState = new NetworkTransformState();
+            if (serializer.IsWriter)
+            {
+                synchronizationState.IsTeleportingNextFrame = true;
+                ApplyTransformToNetworkStateWithInfo(ref synchronizationState, m_CachedNetworkManager.LocalTime.Time, transform);
+                synchronizationState.NetworkSerialize(serializer);
+            }
+            else
+            {
+                synchronizationState.NetworkSerialize(serializer);
+                AddInterpolatedState(synchronizationState);
+            }
+        }
+
         /// <summary>
         /// This will try to send/commit the current transform delta states (if any)
         /// </summary>
@@ -445,28 +495,23 @@ namespace Unity.Netcode.Components
                 return;
             }
 
-            /// If authority is invoking this, then treat it like we do with <see cref="Update"/>
+            // If we are authority, update the authoritative state
             if (CanCommitToTransform)
             {
-                // If our replicated state is not dirty and our local authority state is dirty, clear it.
-                if (!ReplicatedNetworkState.IsDirty() && m_LocalAuthoritativeNetworkState.IsDirty)
-                {
-                    // Now clear our bitset and prepare for next network tick state update
-                    m_LocalAuthoritativeNetworkState.ClearBitSetForNextTick();
-                }
-
-                TryCommitTransform(transformToCommit, m_CachedNetworkManager.LocalTime.Time);
+                UpdateAuthoritativeState(transform);
             }
-            else
+            else // Non-Authority
             {
+                var position = InLocalSpace ? transformToCommit.localPosition : transformToCommit.position;
+                var rotation = InLocalSpace ? transformToCommit.localRotation : transformToCommit.rotation;
                 // We are an owner requesting to update our state
                 if (!m_CachedIsServer)
                 {
-                    SetStateServerRpc(transformToCommit.position, transformToCommit.rotation, transformToCommit.localScale, false);
+                    SetStateServerRpc(position, rotation, transformToCommit.localScale, false);
                 }
                 else // Server is always authoritative (including owner authoritative)
                 {
-                    SetStateClientRpc(transformToCommit.position, transformToCommit.rotation, transformToCommit.localScale, false);
+                    SetStateClientRpc(position, rotation, transformToCommit.localScale, false);
                 }
             }
         }
@@ -483,47 +528,33 @@ namespace Unity.Netcode.Components
                 NetworkLog.LogError($"[{name}] is trying to commit the transform without authority!");
                 return;
             }
-            var isDirty = ApplyTransformToNetworkState(ref m_LocalAuthoritativeNetworkState, dirtyTime, transformToCommit);
 
-            // if dirty, send
-            // if not dirty anymore, but hasn't sent last value for limiting extrapolation, still set isDirty
-            // if not dirty and has already sent last value, don't do anything
-            // extrapolation works by using last two values. if it doesn't receive anything anymore, it'll continue to extrapolate.
-            // This is great in case there's message loss, not so great if we just don't have new values to send.
-            // the following will send one last "copied" value so unclamped interpolation tries to extrapolate between two identical values, effectively
-            // making it immobile.
-            if (isDirty)
+            // If the transform has deltas (returns dirty) then...
+            if (ApplyTransformToNetworkState(ref m_LocalAuthoritativeNetworkState, dirtyTime, transformToCommit))
             {
-                // Commit the state
+                // ...commit the state
                 ReplicatedNetworkState.Value = m_LocalAuthoritativeNetworkState;
-                m_HasSentLastValue = false;
-                m_LastSentTick = m_CachedNetworkManager.LocalTime.Tick;
-                m_LastSentState = m_LocalAuthoritativeNetworkState;
-            }
-            else if (!m_HasSentLastValue && m_CachedNetworkManager.LocalTime.Tick >= m_LastSentTick + 1) // check for state.IsDirty since update can happen more than once per tick. No need for client, RPCs will just queue up
-            {
-                // Since the last m_LocalAuthoritativeNetworkState could have included a IsTeleportingNextFrame
-                // we need to reset this here so only the deltas are applied and interpolation is not reset again.
-                m_LastSentState.IsTeleportingNextFrame = false;
-                m_LastSentState.SentTime = m_CachedNetworkManager.LocalTime.Time; // time 1+ tick later
-                // Commit the state
-                ReplicatedNetworkState.Value = m_LastSentState;
-                m_HasSentLastValue = true;
             }
         }
 
+        /// <summary>
+        /// Initializes the interpolators with the current transform values
+        /// </summary>
         private void ResetInterpolatedStateToCurrentAuthoritativeState()
         {
             var serverTime = NetworkManager.ServerTime.Time;
-            m_PositionXInterpolator.ResetTo(m_LocalAuthoritativeNetworkState.PositionX, serverTime);
-            m_PositionYInterpolator.ResetTo(m_LocalAuthoritativeNetworkState.PositionY, serverTime);
-            m_PositionZInterpolator.ResetTo(m_LocalAuthoritativeNetworkState.PositionZ, serverTime);
+            var position = InLocalSpace ? transform.localPosition : transform.position;
+            m_PositionXInterpolator.ResetTo(position.x, serverTime);
+            m_PositionYInterpolator.ResetTo(position.y, serverTime);
+            m_PositionZInterpolator.ResetTo(position.z, serverTime);
 
-            m_RotationInterpolator.ResetTo(Quaternion.Euler(m_LocalAuthoritativeNetworkState.RotAngleX, m_LocalAuthoritativeNetworkState.RotAngleY, m_LocalAuthoritativeNetworkState.RotAngleZ), serverTime);
+            var rotation = InLocalSpace ? transform.localRotation : transform.rotation;
+            m_RotationInterpolator.ResetTo(rotation, serverTime);
 
-            m_ScaleXInterpolator.ResetTo(m_LocalAuthoritativeNetworkState.ScaleX, serverTime);
-            m_ScaleYInterpolator.ResetTo(m_LocalAuthoritativeNetworkState.ScaleY, serverTime);
-            m_ScaleZInterpolator.ResetTo(m_LocalAuthoritativeNetworkState.ScaleZ, serverTime);
+            var scale = transform.localScale;
+            m_ScaleXInterpolator.ResetTo(scale.x, serverTime);
+            m_ScaleYInterpolator.ResetTo(scale.y, serverTime);
+            m_ScaleZInterpolator.ResetTo(scale.z, serverTime);
         }
 
         /// <summary>
@@ -574,63 +605,63 @@ namespace Unity.Netcode.Components
                 isDirty = true;
             }
 
-            if (SyncPositionX && Mathf.Abs(networkState.PositionX - position.x) >= PositionThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncPositionX && (Mathf.Abs(networkState.PositionX - position.x) >= PositionThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.PositionX = position.x;
                 networkState.HasPositionX = true;
                 isPositionDirty = true;
             }
 
-            if (SyncPositionY && Mathf.Abs(networkState.PositionY - position.y) >= PositionThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncPositionY && (Mathf.Abs(networkState.PositionY - position.y) >= PositionThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.PositionY = position.y;
                 networkState.HasPositionY = true;
                 isPositionDirty = true;
             }
 
-            if (SyncPositionZ && Mathf.Abs(networkState.PositionZ - position.z) >= PositionThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncPositionZ && (Mathf.Abs(networkState.PositionZ - position.z) >= PositionThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.PositionZ = position.z;
                 networkState.HasPositionZ = true;
                 isPositionDirty = true;
             }
 
-            if (SyncRotAngleX && Mathf.Abs(Mathf.DeltaAngle(networkState.RotAngleX, rotAngles.x)) >= RotAngleThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncRotAngleX && (Mathf.Abs(Mathf.DeltaAngle(networkState.RotAngleX, rotAngles.x)) >= RotAngleThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.RotAngleX = rotAngles.x;
                 networkState.HasRotAngleX = true;
                 isRotationDirty = true;
             }
 
-            if (SyncRotAngleY && Mathf.Abs(Mathf.DeltaAngle(networkState.RotAngleY, rotAngles.y)) >= RotAngleThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncRotAngleY && (Mathf.Abs(Mathf.DeltaAngle(networkState.RotAngleY, rotAngles.y)) >= RotAngleThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.RotAngleY = rotAngles.y;
                 networkState.HasRotAngleY = true;
                 isRotationDirty = true;
             }
 
-            if (SyncRotAngleZ && Mathf.Abs(Mathf.DeltaAngle(networkState.RotAngleZ, rotAngles.z)) >= RotAngleThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncRotAngleZ && (Mathf.Abs(Mathf.DeltaAngle(networkState.RotAngleZ, rotAngles.z)) >= RotAngleThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.RotAngleZ = rotAngles.z;
                 networkState.HasRotAngleZ = true;
                 isRotationDirty = true;
             }
 
-            if (SyncScaleX && Mathf.Abs(networkState.ScaleX - scale.x) >= ScaleThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncScaleX && (Mathf.Abs(networkState.ScaleX - scale.x) >= ScaleThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.ScaleX = scale.x;
                 networkState.HasScaleX = true;
                 isScaleDirty = true;
             }
 
-            if (SyncScaleY && Mathf.Abs(networkState.ScaleY - scale.y) >= ScaleThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncScaleY && (Mathf.Abs(networkState.ScaleY - scale.y) >= ScaleThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.ScaleY = scale.y;
                 networkState.HasScaleY = true;
                 isScaleDirty = true;
             }
 
-            if (SyncScaleZ && Mathf.Abs(networkState.ScaleZ - scale.z) >= ScaleThreshold || networkState.IsTeleportingNextFrame)
+            if (SyncScaleZ && (Mathf.Abs(networkState.ScaleZ - scale.z) >= ScaleThreshold || networkState.IsTeleportingNextFrame))
             {
                 networkState.ScaleZ = scale.z;
                 networkState.HasScaleZ = true;
@@ -656,104 +687,92 @@ namespace Unity.Netcode.Components
         private void ApplyAuthoritativeState()
         {
             var networkState = ReplicatedNetworkState.Value;
-            var interpolatedPosition = networkState.InLocalSpace ? transform.localPosition : transform.position;
+            var adjustedPosition = networkState.InLocalSpace ? transform.localPosition : transform.position;
 
-            // todo: we should store network state w/ quats vs. euler angles
-            var interpolatedRotAngles = networkState.InLocalSpace ? transform.localEulerAngles : transform.eulerAngles;
-            var interpolatedScale = transform.localScale;
-            var isTeleporting = networkState.IsTeleportingNextFrame;
+            // TODO: We should store network state w/ quats vs. euler angles
+            var adjustedRotAngles = networkState.InLocalSpace ? transform.localEulerAngles : transform.eulerAngles;
+            var adjustedScale = transform.localScale;
 
             // InLocalSpace Read:
             InLocalSpace = networkState.InLocalSpace;
 
-            // Update the position values that were changed in this state update
-            if (networkState.HasPositionX)
+            // NOTE ABOUT INTERPOLATING AND THE CODE BELOW:
+            // We always apply the interpolated state for any axis we are synchronizing even when the state has no deltas
+            // to assure we fully interpolate to our target even after we stop extrapolating 1 tick later.
+            var useInterpolatedValue = !networkState.IsTeleportingNextFrame && Interpolate;
+            if (useInterpolatedValue)
             {
-                interpolatedPosition.x = isTeleporting || !Interpolate ? networkState.PositionX : m_PositionXInterpolator.GetInterpolatedValue();
-            }
+                if (SyncPositionX) { adjustedPosition.x = m_PositionXInterpolator.GetInterpolatedValue(); }
+                if (SyncPositionY) { adjustedPosition.y = m_PositionYInterpolator.GetInterpolatedValue(); }
+                if (SyncPositionZ) { adjustedPosition.z = m_PositionZInterpolator.GetInterpolatedValue(); }
 
-            if (networkState.HasPositionY)
-            {
-                interpolatedPosition.y = isTeleporting || !Interpolate ? networkState.PositionY : m_PositionYInterpolator.GetInterpolatedValue();
-            }
+                if (SyncScaleX) { adjustedScale.x = m_ScaleXInterpolator.GetInterpolatedValue(); }
+                if (SyncScaleY) { adjustedScale.y = m_ScaleYInterpolator.GetInterpolatedValue(); }
+                if (SyncScaleZ) { adjustedScale.z = m_ScaleZInterpolator.GetInterpolatedValue(); }
 
-            if (networkState.HasPositionZ)
-            {
-                interpolatedPosition.z = isTeleporting || !Interpolate ? networkState.PositionZ : m_PositionZInterpolator.GetInterpolatedValue();
-            }
-
-            // Update the rotation values that were changed in this state update
-            if (networkState.HasRotAngleChange)
-            {
-                var eulerAngles = new Vector3();
-                if (Interpolate)
+                if (SynchronizeRotation)
                 {
-                    eulerAngles = m_RotationInterpolator.GetInterpolatedValue().eulerAngles;
-                }
-
-                if (networkState.HasRotAngleX)
-                {
-                    interpolatedRotAngles.x = isTeleporting || !Interpolate ? networkState.RotAngleX : eulerAngles.x;
-                }
-
-                if (networkState.HasRotAngleY)
-                {
-                    interpolatedRotAngles.y = isTeleporting || !Interpolate ? networkState.RotAngleY : eulerAngles.y;
-                }
-
-                if (networkState.HasRotAngleZ)
-                {
-                    interpolatedRotAngles.z = isTeleporting || !Interpolate ? networkState.RotAngleZ : eulerAngles.z;
+                    var interpolatedEulerAngles = m_RotationInterpolator.GetInterpolatedValue().eulerAngles;
+                    if (SyncRotAngleX) { adjustedRotAngles.x = interpolatedEulerAngles.x; }
+                    if (SyncRotAngleY) { adjustedRotAngles.y = interpolatedEulerAngles.y; }
+                    if (SyncRotAngleZ) { adjustedRotAngles.z = interpolatedEulerAngles.z; }
                 }
             }
-
-            // Update all scale axis that were changed in this state update
-            if (networkState.HasScaleX)
+            else
             {
-                interpolatedScale.x = isTeleporting || !Interpolate ? networkState.ScaleX : m_ScaleXInterpolator.GetInterpolatedValue();
+                if (networkState.HasPositionX) { adjustedPosition.x = networkState.PositionX; }
+                if (networkState.HasPositionY) { adjustedPosition.y = networkState.PositionY; }
+                if (networkState.HasPositionZ) { adjustedPosition.z = networkState.PositionZ; }
+
+                if (networkState.HasScaleX) { adjustedScale.x = networkState.ScaleX; }
+                if (networkState.HasScaleY) { adjustedScale.y = networkState.ScaleY; }
+                if (networkState.HasScaleZ) { adjustedScale.z = networkState.ScaleZ; }
+
+                if (networkState.HasRotAngleX) { adjustedRotAngles.x = networkState.RotAngleX; }
+                if (networkState.HasRotAngleY) { adjustedRotAngles.y = networkState.RotAngleY; }
+                if (networkState.HasRotAngleZ) { adjustedRotAngles.z = networkState.RotAngleZ; }
             }
 
-            if (networkState.HasScaleY)
-            {
-                interpolatedScale.y = isTeleporting || !Interpolate ? networkState.ScaleY : m_ScaleYInterpolator.GetInterpolatedValue();
-            }
+            // NOTE: The below conditional checks for applying axial values are required in order to
+            // prevent the non-authoritative side from making adjustments when interpolation is off.
 
-            if (networkState.HasScaleZ)
-            {
-                interpolatedScale.z = isTeleporting || !Interpolate ? networkState.ScaleZ : m_ScaleZInterpolator.GetInterpolatedValue();
-            }
+            // TODO: Determine if we want to enforce, frame by frame, the non-authoritative transform values.
+            // We would want save the position, rotation, and scale (each individually) after applying each
+            // authoritative transform state received. Otherwise, the non-authoritative side could make
+            // changes to an axial value (if interpolation is turned off) until authority sends an update for
+            // that same axial value. When interpolation is on, the state's values being synchronized are
+            // always applied each frame.
 
-            // Apply the new position
-            if (networkState.HasPositionChange)
+            // Apply the new position if it has changed or we are interpolating and synchronizing position
+            if (networkState.HasPositionChange || (useInterpolatedValue && SynchronizePosition))
             {
                 if (InLocalSpace)
                 {
-
-                    transform.localPosition = interpolatedPosition;
+                    transform.localPosition = adjustedPosition;
                 }
                 else
                 {
-                    transform.position = interpolatedPosition;
+                    transform.position = adjustedPosition;
                 }
             }
 
-            // Apply the new rotation
-            if (networkState.HasRotAngleChange)
+            // Apply the new rotation if it has changed or we are interpolating and synchronizing rotation
+            if (networkState.HasRotAngleChange || (useInterpolatedValue && SynchronizeRotation))
             {
                 if (InLocalSpace)
                 {
-                    transform.localRotation = Quaternion.Euler(interpolatedRotAngles);
+                    transform.localRotation = Quaternion.Euler(adjustedRotAngles);
                 }
                 else
                 {
-                    transform.rotation = Quaternion.Euler(interpolatedRotAngles);
+                    transform.rotation = Quaternion.Euler(adjustedRotAngles);
                 }
             }
 
-            // Apply the new scale
-            if (networkState.HasScaleChange)
+            // Apply the new scale if it has changed or we are interpolating and synchronizing scale
+            if (networkState.HasScaleChange || (useInterpolatedValue && SynchronizeScale))
             {
-                transform.localScale = interpolatedScale;
+                transform.localScale = adjustedScale;
             }
         }
 
@@ -910,6 +929,7 @@ namespace Unity.Netcode.Components
                 }
 
                 currentRotation.eulerAngles = currentEulerAngles;
+
                 m_RotationInterpolator.AddMeasurement(currentRotation, sentTime);
             }
         }
@@ -932,6 +952,7 @@ namespace Unity.Netcode.Components
 
             if (Interpolate)
             {
+                // Add measurements for the new state's deltas
                 AddInterpolatedState(newState);
             }
         }
@@ -954,18 +975,25 @@ namespace Unity.Netcode.Components
             m_ScaleZInterpolator.MaxInterpolationBound = maxInterpolationBound;
         }
 
+        /// <summary>
+        /// Create interpolators when first instantiated to avoid memory allocations if the
+        /// associated NetworkObject persists (i.e. despawned but not destroyed or pools)
+        /// </summary>
         private void Awake()
         {
-            // we only want to create our interpolators during Awake so that, when pooled, we do not create tons
-            //  of gc thrash each time objects wink out and are re-used
+            // Rotation is a single Quaternion since each Euler axis will affect the quaternion's final value
+            m_RotationInterpolator = new BufferedLinearInterpolatorQuaternion();
+
+            // All other interpolators are BufferedLinearInterpolatorFloats
             m_PositionXInterpolator = new BufferedLinearInterpolatorFloat();
             m_PositionYInterpolator = new BufferedLinearInterpolatorFloat();
             m_PositionZInterpolator = new BufferedLinearInterpolatorFloat();
-            m_RotationInterpolator = new BufferedLinearInterpolatorQuaternion(); // rotation is a single Quaternion since each euler axis will affect the quaternion's final value
             m_ScaleXInterpolator = new BufferedLinearInterpolatorFloat();
             m_ScaleYInterpolator = new BufferedLinearInterpolatorFloat();
             m_ScaleZInterpolator = new BufferedLinearInterpolatorFloat();
 
+            // Used to quickly iteration over the BufferedLinearInterpolatorFloat
+            // instances
             if (m_AllFloatInterpolators.Count == 0)
             {
                 m_AllFloatInterpolators.Add(m_PositionXInterpolator);
@@ -990,8 +1018,10 @@ namespace Unity.Netcode.Components
             // that can be invoked when ownership changes.
             if (CanCommitToTransform)
             {
+                var currentPosition = InLocalSpace ? transform.localPosition : transform.position;
+                var currentRotation = InLocalSpace ? transform.localRotation : transform.rotation;
                 // Teleport to current position
-                SetStateInternal(transform.position, transform.rotation, transform.localScale, true);
+                SetStateInternal(currentPosition, currentRotation, transform.localScale, true);
 
                 // Force the state update to be sent
                 TryCommitTransform(transform, m_CachedNetworkManager.LocalTime.Time);
@@ -1115,8 +1145,7 @@ namespace Unity.Netcode.Components
             }
             else
             {
-                transform.position = pos;
-                transform.rotation = rot;
+                transform.SetPositionAndRotation(pos, rot);
             }
             transform.localScale = scale;
             m_LocalAuthoritativeNetworkState.IsTeleportingNextFrame = shouldTeleport;
@@ -1134,11 +1163,7 @@ namespace Unity.Netcode.Components
         private void SetStateClientRpc(Vector3 pos, Quaternion rot, Vector3 scale, bool shouldTeleport, ClientRpcParams clientRpcParams = default)
         {
             // Server dictated state is always applied
-            transform.position = pos;
-            transform.rotation = rot;
-            transform.localScale = scale;
-            m_LocalAuthoritativeNetworkState.IsTeleportingNextFrame = shouldTeleport;
-            TryCommitTransform(transform, m_CachedNetworkManager.LocalTime.Time);
+            SetStateInternal(pos, rot, scale, shouldTeleport);
         }
 
         /// <summary>
@@ -1155,16 +1180,28 @@ namespace Unity.Netcode.Components
             {
                 (pos, rot, scale) = OnClientRequestChange(pos, rot, scale);
             }
-
-            transform.position = pos;
-            transform.rotation = rot;
-            transform.localScale = scale;
-            m_LocalAuthoritativeNetworkState.IsTeleportingNextFrame = shouldTeleport;
-            TryCommitTransform(transform, m_CachedNetworkManager.LocalTime.Time);
+            SetStateInternal(pos, rot, scale, shouldTeleport);
+        }
+
+        /// <summary>
+        /// Will update the authoritative transform state if any deltas are detected.
+        /// This will also reset the m_LocalAuthoritativeNetworkState if it is still dirty
+        /// but the replicated network state is not.
+        /// </summary>
+        /// <param name="transformSource">transform to be updated</param>
+        private void UpdateAuthoritativeState(Transform transformSource)
+        {
+            // If our replicated state is not dirty and our local authority state is dirty, clear it.
+            if (!ReplicatedNetworkState.IsDirty() && m_LocalAuthoritativeNetworkState.IsDirty)
+            {
+                m_LastSentState = m_LocalAuthoritativeNetworkState;
+                // Now clear our bitset and prepare for next network tick state update
+                m_LocalAuthoritativeNetworkState.ClearBitSetForNextTick();
+            }
+
+            TryCommitTransform(transformSource, m_CachedNetworkManager.LocalTime.Time);
         }
 
-        // todo: this is currently in update, to be able to catch any transform changes. A FixedUpdate mode could be added to be less intense, but it'd be
-        // conditional to users only making transform update changes in FixedUpdate.
         /// <inheritdoc/>
         /// <remarks>
         /// If you override this method, be sure that:
@@ -1179,21 +1216,15 @@ namespace Unity.Netcode.Components
                 return;
             }
 
+            // If we are authority, update the authoritative state
             if (CanCommitToTransform)
             {
-                // If our replicated state is not dirty and our local authority state is dirty, clear it.
-                if (!ReplicatedNetworkState.IsDirty() && m_LocalAuthoritativeNetworkState.IsDirty)
-                {
-                    // Now clear our bitset and prepare for next network tick state update
-                    m_LocalAuthoritativeNetworkState.ClearBitSetForNextTick();
-                }
-                TryCommitTransform(transform, m_CachedNetworkManager.LocalTime.Time);
+                UpdateAuthoritativeState(transform);
             }
-            else
+            else // Non-Authority
             {
                 if (Interpolate)
                 {
-                    // eventually, we could hoist this calculation so that it happens once for all objects, not once per object
                     var serverTime = NetworkManager.ServerTime;
                     var cachedDeltaTime = Time.deltaTime;
                     var cachedServerTime = serverTime.Time;
@@ -1205,7 +1236,8 @@ namespace Unity.Netcode.Components
 
                     m_RotationInterpolator.Update(cachedDeltaTime, cachedRenderTime, cachedServerTime);
                 }
-                // Now apply the current authoritative state
+
+                // Apply the current authoritative state
                 ApplyAuthoritativeState();
             }
         }

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;
@@ -17,8 +16,7 @@ namespace Unity.Netcode.Editor.CodeGen
     {
         public override ILPPInterface GetInstance() => this;
 
-        public override bool WillProcess(ICompiledAssembly compiledAssembly) =>
-            compiledAssembly.Name == CodeGenHelpers.RuntimeAssemblyName;
+        public override bool WillProcess(ICompiledAssembly compiledAssembly) => compiledAssembly.Name == CodeGenHelpers.RuntimeAssemblyName;
 
         private readonly List<DiagnosticMessage> m_Diagnostics = new List<DiagnosticMessage>();
 
@@ -32,13 +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)
@@ -60,7 +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
@@ -91,77 +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);
-            m_MessagingSystem_MessageWithHandler_TypeRef = moduleDefinition.ImportReference(messageWithHandlerType);
-            foreach (var fieldInfo in messageWithHandlerType.GetFields())
+            TypeDefinition messageHandlerTypeDef = null;
+            TypeDefinition versionGetterTypeDef = null;
+            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 methodInfo in typeType.GetMethods())
+            foreach (var methodDef in typeTypeDef.Methods)
             {
-                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 fieldInfo in ilppMessageProviderType.GetFields(BindingFlags.Static | BindingFlags.NonPublic))
+            foreach (var fieldDef in ilppMessageProviderTypeDef.Fields)
             {
-                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 methodInfo in listType.GetMethods())
+            foreach (var methodDef in listTypeDef.Methods)
             {
-                switch (methodInfo.Name)
+                switch (methodDef.Name)
                 {
-                    case nameof(List<MessagingSystem.MessageWithHandler>.Add):
-                        m_List_Add_MethodRef = moduleDefinition.ImportReference(methodInfo);
+                    case "Add":
+                        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 methodInfo in messagingSystemType.GetMethods(BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public))
+            foreach (var methodDef in messagingSystemTypeDef.Methods)
             {
-                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;
                 }
             }
@@ -188,7 +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));
@@ -204,7 +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));
 
@@ -212,15 +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
-        // 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)
+        // Creates a static module constructor (which is executed when the module is loaded) that registers all the 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).
         // 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)
@@ -239,7 +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) =>
-            compiledAssembly.References.Any(filePath => Path.GetFileNameWithoutExtension(filePath) == CodeGenHelpers.RuntimeAssemblyName);
+        public override bool WillProcess(ICompiledAssembly compiledAssembly) => 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 List<MethodReference> m_FastBufferWriter_ExtensionMethodRefs = new List<MethodReference>();
+        private readonly Dictionary<string, MethodReference> m_FastBufferWriter_WriteValue_MethodRefs = new Dictionary<string, 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 List<MethodReference> m_FastBufferReader_ExtensionMethodRefs = new List<MethodReference>();
+        private readonly Dictionary<string, MethodReference> m_FastBufferReader_ReadValue_MethodRefs = new Dictionary<string, 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);
-            foreach (var methodInfo in debugType.GetMethods())
+            TypeDefinition debugTypeDef = null;
+            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(networkManagerType);
-            foreach (var propertyInfo in networkManagerType.GetProperties())
+            m_NetworkManager_TypeRef = moduleDefinition.ImportReference(networkManagerTypeDef);
+            foreach (var propertyDef in networkManagerTypeDef.Properties)
             {
-                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_Add_MethodRef = moduleDefinition.ImportReference(fieldInfo.FieldType.GetMethod("Add"));
+                        m_NetworkManager_rpc_func_table_FieldRef = moduleDefinition.ImportReference(fieldDef);
+
+                        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_Add_MethodRef = moduleDefinition.ImportReference(fieldInfo.FieldType.GetMethod("Add"));
+                        m_NetworkManager_rpc_name_table_FieldRef = moduleDefinition.ImportReference(fieldDef);
+
+                        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(networkBehaviourType);
-            foreach (var propertyInfo in networkBehaviourType.GetProperties())
+            m_NetworkBehaviour_TypeRef = moduleDefinition.ImportReference(networkBehaviourTypeDef);
+            foreach (var propertyDef in networkBehaviourTypeDef.Properties)
             {
-                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);
-            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())
+            foreach (var ctor in networkHandlerDelegateTypeDef.Resolve().GetConstructors())
             {
-                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(serverRpcParamsType);
-            foreach (var fieldInfo in serverRpcParamsType.GetFields())
+            m_ServerRpcParams_TypeRef = moduleDefinition.ImportReference(serverRpcParamsTypeDef);
+            foreach (var fieldDef in serverRpcParamsTypeDef.Fields)
             {
-                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(clientRpcParamsType);
+            m_ClientRpcParams_TypeRef = moduleDefinition.ImportReference(clientRpcParamsTypeDef);
+            m_FastBufferWriter_TypeRef = moduleDefinition.ImportReference(fastBufferWriterTypeDef);
+            m_FastBufferReader_TypeRef = moduleDefinition.ImportReference(fastBufferReaderTypeDef);
 
-            var fastBufferWriterType = typeof(FastBufferWriter);
-            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.
+            // 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.Resolve() == paramType.Resolve() &&
+                            if (parameters[1].ParameterType.FullName == paramType.FullName &&
                                 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: 3ada9e8fd5bf94b1f9a6a21531c8a3ee
+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_NetworkVariableFields.Add(fields[i].Name, fields[i]);
+                    m_NetworkVariableNames.Add(ObjectNames.NicifyVariableName(fields[i].Name));
+                    m_NetworkVariableFields.Add(ObjectNames.NicifyVariableName(fields[i].Name), fields[i]);
                 }
             }
         }
@@ -230,8 +234,6 @@ 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>
@@ -263,8 +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 (networkManager == null)
+            if (!rootTransform.TryGetComponent<NetworkManager>(out var networkManager))
             {
                 networkManager = rootTransform.GetComponentInChildren<NetworkManager>();
             }
@@ -299,8 +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 (networkObject == null)
+            if (!rootTransform.TryGetComponent<NetworkObject>(out var networkObject))
             {
                 networkObject = rootTransform.GetComponentInChildren<NetworkObject>();
 
@@ -310,7 +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.");
@@ -319,7 +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();
@@ -329,20 +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

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using UnityEditor;
 using UnityEngine;
 using UnityEditorInternal;
+using Unity.Netcode.Editor.Configuration;
 
 namespace Unity.Netcode.Editor
 {
@@ -14,7 +15,6 @@ namespace Unity.Netcode.Editor
     [CanEditMultipleObjects]
     public class NetworkManagerEditor : UnityEditor.Editor
     {
-        internal const string InstallMultiplayerToolsTipDismissedPlayerPrefKey = "Netcode_Tip_InstallMPTools_Dismissed";
         private static GUIStyle s_CenteredWordWrappedLabelStyle;
         private static GUIStyle s_HelpBoxStyle;
 
@@ -214,18 +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();
@@ -371,7 +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;
             }
@@ -417,7 +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

@@ -15,6 +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)
@@ -95,7 +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/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/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);
 
@@ -235,14 +236,42 @@ 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)
                 {
-                    NetworkManager.NetworkMetrics.TrackRpcSent(
-                        client.Key,
-                        NetworkObject,
-                        rpcMethodName,
-                        __getTypeName(),
-                        rpcWriteSize);
+                    foreach (var targetClientId in clientRpcParams.Send.TargetClientIds)
+                    {
+                        NetworkManager.NetworkMetrics.TrackRpcSent(
+                            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
@@ -307,23 +347,29 @@ 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
             {
-                if (m_NetworkObject == null)
+                try
                 {
-                    m_NetworkObject = GetComponentInParent<NetworkObject>();
+                    if (m_NetworkObject == null)
+                    {
+                        m_NetworkObject = GetComponentInParent<NetworkObject>();
+                    }
+                }
+                catch (Exception)
+                {
+                    return null;
                 }
 
                 // ShutdownInProgress check:
@@ -436,14 +482,41 @@ namespace Unity.Netcode
             IsSpawned = true;
             InitializeVariables();
             UpdateNetworkProperties();
-            OnNetworkSpawn();
+        }
+
+        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();
-            OnNetworkDespawn();
+            try
+            {
+                OnNetworkDespawn();
+            }
+            catch (Exception e)
+            {
+                Debug.LogException(e);
+            }
         }
 
         /// <summary>
@@ -576,12 +649,24 @@ namespace Unity.Netcode
             NetworkVariableIndexesToResetSet.Clear();
         }
 
-        internal void PostNetworkVariableWrite()
+        internal void PostNetworkVariableWrite(bool forced = false)
         {
-            // mark any variables we wrote as no longer dirty
-            for (int i = 0; i < NetworkVariableIndexesToReset.Count; i++)
+            if (forced)
             {
-                NetworkVariableFields[NetworkVariableIndexesToReset[i]].ResetDirty();
+                // 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++)
+                {
+                    NetworkVariableFields[NetworkVariableIndexesToReset[i]].ResetDirty();
+                }
             }
 
             MarkVariablesDirty(false);
@@ -645,7 +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
@@ -678,6 +763,14 @@ namespace Unity.Netcode
             }
         }
 
+        /// <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)
@@ -687,27 +780,47 @@ namespace Unity.Netcode
 
             for (int j = 0; j < NetworkVariableFields.Count; j++)
             {
-                bool canClientRead = NetworkVariableFields[j].CanClientRead(targetClientId);
 
-                if (canClientRead)
+                if (NetworkVariableFields[j].CanClientRead(targetClientId))
                 {
-                    var writePos = writer.Position;
-                    writer.WriteValueSafe((ushort)0);
-                    var startPos = writer.Position;
-                    NetworkVariableFields[j].WriteField(writer);
-                    var size = writer.Position - startPos;
-                    writer.Seek(writePos);
-                    writer.WriteValueSafe((ushort)size);
-                    writer.Seek(startPos + size);
+                    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);
+                        var size = writer.Position - startPos;
+                        writer.Seek(writePos);
+                        writer.WriteValueSafe((ushort)size);
+                        writer.Seek(startPos + size);
+                    }
+                    else
+                    {
+                        NetworkVariableFields[j].WriteField(writer);
+                    }
                 }
-                else
+                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)
             {
@@ -716,13 +829,23 @@ namespace Unity.Netcode
 
             for (int j = 0; j < NetworkVariableFields.Count; j++)
             {
-                reader.ReadValueSafe(out ushort varSize);
-                if (varSize == 0)
+                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)
@@ -759,6 +882,138 @@ 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

Runtime/Core/NetworkBehaviourUpdater.cs

@@ -26,6 +26,10 @@ 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)
                 {
                     foreach (var dirtyObj in m_DirtyNetworkObjects)
@@ -38,10 +42,6 @@ namespace Unity.Netcode
                         for (int i = 0; i < networkManager.ConnectedClientsList.Count; i++)
                         {
                             var client = networkManager.ConnectedClientsList[i];
-                            if (networkManager.IsHost && client.ClientId == networkManager.LocalClientId)
-                            {
-                                continue;
-                            }
 
                             if (dirtyObj.IsNetworkVisibleTo(client.ClientId))
                             {
@@ -75,10 +75,7 @@ namespace Unity.Netcode
                 // Now, reset all the no-longer-dirty variables
                 foreach (var dirtyobj in m_DirtyNetworkObjects)
                 {
-                    for (int k = 0; k < dirtyobj.ChildNetworkBehaviours.Count; k++)
-                    {
-                        dirtyobj.ChildNetworkBehaviours[k].PostNetworkVariableWrite();
-                    }
+                    dirtyobj.PostNetworkVariableWrite();
                 }
                 m_DirtyNetworkObjects.Clear();
             }

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
@@ -51,7 +51,7 @@ 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; set; }
@@ -86,6 +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;
@@ -187,8 +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 (networkObject != null)
+            if (gameObject.TryGetComponent<NetworkObject>(out var networkObject))
             {
                 if (NetworkConfig.NetworkPrefabOverrideLinks.ContainsKey(networkObject.GlobalObjectIdHash))
                 {
@@ -367,10 +372,22 @@ 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>
@@ -432,6 +449,12 @@ namespace Unity.Netcode
             /// 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>
@@ -519,8 +542,7 @@ namespace Unity.Netcode
                 var networkPrefabGo = networkPrefab?.Prefab;
                 if (networkPrefabGo != null)
                 {
-                    var networkObject = networkPrefabGo.GetComponent<NetworkObject>();
-                    if (networkObject == null)
+                    if (!networkPrefabGo.TryGetComponent<NetworkObject>(out var networkObject))
                     {
                         if (NetworkLog.CurrentLogLevel <= LogLevel.Normal)
                         {
@@ -695,8 +717,7 @@ namespace Unity.Netcode
             }
             else if (networkPrefab.Override == NetworkPrefabOverride.None)
             {
-                networkObject = networkPrefab.Prefab.GetComponent<NetworkObject>();
-                if (networkObject == null)
+                if (!networkPrefab.Prefab.TryGetComponent(out networkObject))
                 {
                     if (NetworkLog.CurrentLogLevel <= LogLevel.Error)
                     {
@@ -742,8 +763,7 @@ namespace Unity.Netcode
                             }
                             else
                             {
-                                networkObject = networkPrefab.SourcePrefabToOverride.GetComponent<NetworkObject>();
-                                if (networkObject == null)
+                                if (!networkPrefab.SourcePrefabToOverride.TryGetComponent(out networkObject))
                                 {
                                     if (NetworkLog.CurrentLogLevel <= LogLevel.Error)
                                     {
@@ -881,6 +901,9 @@ namespace Unity.Netcode
                 return;
             }
 
+            DisconnectReason = string.Empty;
+            IsApproved = false;
+
             ComponentFactory.SetDefaults();
 
             if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
@@ -968,8 +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 (playerPrefabNetworkObject != null)
+                if (NetworkConfig.PlayerPrefab.TryGetComponent<NetworkObject>(out var playerPrefabNetworkObject))
                 {
                     //In the event there is no NetworkPrefab entry (i.e. no override for default player prefab)
                     if (!NetworkConfig.NetworkPrefabOverrideLinks.ContainsKey(playerPrefabNetworkObject
@@ -1023,24 +1045,38 @@ namespace Unity.Netcode
             }
 
             Initialize(true);
+            IsServer = true;
+            IsClient = false;
+            IsListening = true;
 
-            // If we failed to start then shutdown and notify user that the transport failed to start
-            if (NetworkConfig.NetworkTransport.StartServer())
+            try
             {
-                IsServer = true;
-                IsClient = false;
-                IsListening = true;
+                // If we failed to start then shutdown and notify user that the transport failed to start
+                if (NetworkConfig.NetworkTransport.StartServer())
+                {
+                    SpawnManager.ServerSpawnSceneObjectsOnStartSweep();
 
-                SpawnManager.ServerSpawnSceneObjectsOnStartSweep();
+                    OnServerStarted?.Invoke();
+                    IsApproved = true;
+                    return true;
+                }
+                else
+                {
+                    IsServer = false;
+                    IsClient = false;
+                    IsListening = false;
 
-                OnServerStarted?.Invoke();
-                return true;
+                    Debug.LogError($"Server is shutting down due to network transport start failure of {NetworkConfig.NetworkTransport.GetType().Name}!");
+                    OnTransportFailure?.Invoke();
+                    Shutdown();
+                }
             }
-            else
+            catch (Exception)
             {
-                Debug.LogError($"Server is shutting down due to network transport start failure of {NetworkConfig.NetworkTransport.GetType().Name}!");
-                OnTransportFailure?.Invoke();
-                Shutdown();
+                IsServer = false;
+                IsClient = false;
+                IsListening = false;
+                throw;
             }
 
             return false;
@@ -1098,23 +1134,38 @@ 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 = true;
+            IsListening = true;
+
+            try
             {
-                Debug.LogError($"Server is shutting down due to network transport start failure of {NetworkConfig.NetworkTransport.GetType().Name}!");
-                OnTransportFailure?.Invoke();
-                Shutdown();
-                return false;
+                // If we failed to start then shutdown and notify user that the transport failed to start
+                if (!NetworkConfig.NetworkTransport.StartServer())
+                {
+                    Debug.LogError($"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();
@@ -1128,6 +1179,7 @@ namespace Unity.Netcode
                 }
 
                 response.Approved = true;
+                IsApproved = true;
                 HandleConnectionApproval(ServerClientId, response);
             }
             else
@@ -1142,6 +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;
@@ -1302,6 +1359,7 @@ namespace Unity.Netcode
         private void DisconnectRemoteClient(ulong clientId)
         {
             var transportId = ClientIdToTransportId(clientId);
+            MessagingSystem.ProcessSendQueues();
             NetworkConfig.NetworkTransport.DisconnectRemoteClient(transportId);
         }
 
@@ -1382,13 +1440,14 @@ 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
@@ -1539,6 +1598,7 @@ namespace Unity.Netcode
             } while (IsListening && networkEvent != NetworkEvent.Nothing);
 
             MessagingSystem.ProcessIncomingMessageQueue();
+            MessagingSystem.CleanupDisconnectedClients();
 
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
             s_TransportPoll.End();
@@ -1560,7 +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);
@@ -1569,7 +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);
             }
         }
 
@@ -1614,32 +1674,100 @@ 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 ((LocalTime - timeStarted).Time < NetworkConfig.ClientConnectionBufferTimeout && PendingClients.ContainsKey(clientId))
+            while (IsListening && !ShutdownInProgress && !timedOut && !connectionApproved)
             {
                 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.");
+                    }
                 }
 
-                DisconnectClient(clientId);
+                if (IsServer)
+                {
+                    DisconnectClient(clientId);
+                }
+                else
+                {
+                    Shutdown(true);
+                }
             }
         }
 
@@ -1729,7 +1857,18 @@ namespace Unity.Netcode
                         NetworkLog.LogInfo($"Disconnect Event From {clientId}");
                     }
 
-                    OnClientDisconnectCallback?.Invoke(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)
                     {
@@ -1895,12 +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);
         }
@@ -1916,13 +2074,20 @@ namespace Unity.Netcode
                     var playerObject = networkClient.PlayerObject;
                     if (playerObject != null)
                     {
-                        if (PrefabHandler.ContainsHandler(ConnectedClients[clientId].PlayerObject.GlobalObjectIdHash))
+                        if (!playerObject.DontDestroyWithOwner)
                         {
-                            PrefabHandler.HandleNetworkPrefabDestroy(ConnectedClients[clientId].PlayerObject);
+                            if (PrefabHandler.ContainsHandler(ConnectedClients[clientId].PlayerObject.GlobalObjectIdHash))
+                            {
+                                PrefabHandler.HandleNetworkPrefabDestroy(ConnectedClients[clientId].PlayerObject);
+                            }
+                            else
+                            {
+                                Destroy(playerObject.gameObject);
+                            }
                         }
                         else
                         {
-                            Destroy(playerObject.gameObject);
+                            playerObject.RemoveOwnership();
                         }
                     }
 
@@ -2033,14 +2198,28 @@ namespace Unity.Netcode
 
                 if (response.CreatePlayerObject)
                 {
-                    var networkObject = SpawnManager.CreateLocalNetworkObject(
-                        isSceneObject: false,
-                        response.PlayerPrefabHash ?? NetworkConfig.PlayerPrefab.GetComponent<NetworkObject>().GlobalObjectIdHash,
-                        ownerClientId,
-                        parentNetworkId: null,
-                        networkSceneHandle: null,
-                        response.Position,
-                        response.Rotation);
+                    var playerPrefabHash = response.PlayerPrefabHash ?? NetworkConfig.PlayerPrefab.GetComponent<NetworkObject>().GlobalObjectIdHash;
+
+                    // Generate a SceneObject for the player object to spawn
+                    var sceneObject = new NetworkObject.SceneObject
+                    {
+                        OwnerClientId = ownerClientId,
+                        IsPlayerObject = true,
+                        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(),
@@ -2068,22 +2247,23 @@ namespace Unity.Netcode
                         }
                     }
 
-                    SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, ownerClientId);
-
+                    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 orderingMessage = new OrderingMessage
+                            var type = MessagingSystem.MessageTypes[index];
+                            message.MessageVersions[index] = new MessageVersionData
                             {
-                                Order = index,
-                                Hash = XXHash.Hash32(MessagingSystem.MessageTypes[index].FullName)
+                                Hash = XXHash.Hash32(type.FullName),
+                                Version = MessagingSystem.GetLocalVersion(type)
                             };
-
-                            SendMessage(ref orderingMessage, NetworkDelivery.ReliableFragmentedSequenced, ownerClientId);
                         }
                     }
 
+                    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)
                     {
@@ -2098,7 +2278,6 @@ namespace Unity.Netcode
                 {
                     LocalClient = client;
                     SpawnManager.UpdateObservedNetworkObjects(ownerClientId);
-                    InvokeOnClientConnectedCallback(ownerClientId);
                 }
 
                 if (!response.CreatePlayerObject || (response.PlayerPrefabHash == null && NetworkConfig.PlayerPrefab == null))
@@ -2111,6 +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);
             }
@@ -2137,11 +2325,11 @@ namespace Unity.Netcode
                 {
                     ObjectInfo = ConnectedClients[clientId].PlayerObject.GetMessageSceneObject(clientPair.Key)
                 };
-                message.ObjectInfo.Header.Hash = playerPrefabHash;
-                message.ObjectInfo.Header.IsSceneObject = false;
-                message.ObjectInfo.Header.HasParent = false;
-                message.ObjectInfo.Header.IsPlayerObject = true;
-                message.ObjectInfo.Header.OwnerClientId = clientId;
+                message.ObjectInfo.Hash = playerPrefabHash;
+                message.ObjectInfo.IsSceneObject = false;
+                message.ObjectInfo.HasParent = false;
+                message.ObjectInfo.IsPlayerObject = true;
+                message.ObjectInfo.OwnerClientId = clientId;
                 var size = SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, clientPair.Key);
                 NetworkMetrics.TrackObjectSpawnSent(clientPair.Key, ConnectedClients[clientId].PlayerObject, size);
             }

Runtime/Core/NetworkObject.cs

@@ -9,7 +9,7 @@ namespace Unity.Netcode
     /// <summary>
     /// A component used to identify that a GameObject in the network
     /// </summary>
-    [AddComponentMenu("Netcode/" + nameof(NetworkObject), -99)]
+    [AddComponentMenu("Netcode/Network Object", -99)]
     [DisallowMultipleComponent]
     public sealed class NetworkObject : MonoBehaviour
     {
@@ -129,7 +129,7 @@ namespace Unity.Netcode
 
         /// <summary>
         /// Whether or not to destroy this object if it's owner is destroyed.
-        /// If false, the objects ownership will be given to the server.
+        /// If true, the objects ownership will be given to the server.
         /// </summary>
         public bool DontDestroyWithOwner;
 
@@ -435,7 +435,7 @@ namespace Unity.Netcode
         private void OnDestroy()
         {
             if (NetworkManager != null && NetworkManager.IsListening && NetworkManager.IsServer == false && IsSpawned &&
-                (IsSceneObject == null || (IsSceneObject != null && IsSceneObject.Value != true)))
+                (IsSceneObject == null || (IsSceneObject.Value != true)))
             {
                 throw new NotServerException($"Destroy a spawned {nameof(NetworkObject)} on a non-host client is not valid. Call {nameof(Destroy)} or {nameof(Despawn)} on the server/host instead.");
             }
@@ -509,6 +509,7 @@ namespace Unity.Netcode
         /// <param name="destroy">(true) the <see cref="GameObject"/> will be destroyed (false) the <see cref="GameObject"/> will persist after being despawned</param>
         public void Despawn(bool destroy = true)
         {
+            MarkVariablesDirty(false);
             NetworkManager.SpawnManager.DespawnObject(this, destroy);
         }
 
@@ -572,21 +573,21 @@ namespace Unity.Netcode
             }
         }
 
-        private bool m_IsReparented; // Did initial parent (came from the scene hierarchy) change at runtime?
         private ulong? m_LatestParent; // What is our last set parent NetworkObject's ID?
         private Transform m_CachedParent; // What is our last set parent Transform reference?
+        private bool m_CachedWorldPositionStays = true; // Used to preserve the world position stays parameter passed in TrySetParent
 
         internal void SetCachedParent(Transform parentTransform)
         {
             m_CachedParent = parentTransform;
         }
 
-        internal (bool IsReparented, ulong? LatestParent) GetNetworkParenting() => (m_IsReparented, m_LatestParent);
+        internal ulong? GetNetworkParenting() => m_LatestParent;
 
-        internal void SetNetworkParenting(bool isReparented, ulong? latestParent)
+        internal void SetNetworkParenting(ulong? latestParent, bool worldPositionStays)
         {
-            m_IsReparented = isReparented;
             m_LatestParent = latestParent;
+            m_CachedWorldPositionStays = worldPositionStays;
         }
 
         /// <summary>
@@ -597,7 +598,10 @@ namespace Unity.Netcode
         /// <returns>Whether or not reparenting was successful.</returns>
         public bool TrySetParent(Transform parent, bool worldPositionStays = true)
         {
-            return TrySetParent(parent.GetComponent<NetworkObject>(), worldPositionStays);
+            var networkObject = parent.GetComponent<NetworkObject>();
+
+            // If the parent doesn't have a NetworkObjet then return false, otherwise continue trying to parent
+            return networkObject == null ? false : TrySetParent(networkObject, worldPositionStays);
         }
 
         /// <summary>
@@ -608,7 +612,37 @@ namespace Unity.Netcode
         /// <returns>Whether or not reparenting was successful.</returns>
         public bool TrySetParent(GameObject parent, bool worldPositionStays = true)
         {
-            return TrySetParent(parent.GetComponent<NetworkObject>(), worldPositionStays);
+            // If we are removing ourself from a parent
+            if (parent == null)
+            {
+                return TrySetParent((NetworkObject)null, worldPositionStays);
+            }
+
+            var networkObject = parent.GetComponent<NetworkObject>();
+
+            // If the parent doesn't have a NetworkObjet then return false, otherwise continue trying to parent
+            return networkObject == null ? false : TrySetParent(networkObject, worldPositionStays);
+        }
+
+        /// <summary>
+        /// Used when despawning the parent, we want to preserve the cached WorldPositionStays value
+        /// </summary>
+        internal bool TryRemoveParentCachedWorldPositionStays()
+        {
+            return TrySetParent((NetworkObject)null, m_CachedWorldPositionStays);
+        }
+
+        /// <summary>
+        /// Removes the parent of the NetworkObject's transform
+        /// </summary>
+        /// <remarks>
+        /// This is a more convenient way to remove the parent without  having to cast the null value to either <see cref="GameObject"/> or <see cref="NetworkObject"/>
+        /// </remarks>
+        /// <param name="worldPositionStays">If true, the parent-relative position, scale and rotation are modified such that the object keeps the same world space position, rotation and scale as before.</param>
+        /// <returns></returns>
+        public bool TryRemoveParent(bool worldPositionStays = true)
+        {
+            return TrySetParent((NetworkObject)null, worldPositionStays);
         }
 
         /// <summary>
@@ -639,17 +673,21 @@ namespace Unity.Netcode
                 return false;
             }
 
+            if (parent != null && !parent.IsSpawned)
+            {
+                return false;
+            }
+            m_CachedWorldPositionStays = worldPositionStays;
+
             if (parent == null)
             {
-                return false;
+                transform.SetParent(null, worldPositionStays);
             }
-
-            if (!parent.IsSpawned)
+            else
             {
-                return false;
+                transform.SetParent(parent.transform, worldPositionStays);
             }
 
-            transform.SetParent(parent.transform, worldPositionStays);
             return true;
         }
 
@@ -685,12 +723,11 @@ namespace Unity.Netcode
                 Debug.LogException(new SpawnStateException($"{nameof(NetworkObject)} can only be reparented after being spawned"));
                 return;
             }
-
+            var removeParent = false;
             var parentTransform = transform.parent;
             if (parentTransform != null)
             {
-                var parentObject = transform.parent.GetComponent<NetworkObject>();
-                if (parentObject == null)
+                if (!transform.parent.TryGetComponent<NetworkObject>(out var parentObject))
                 {
                     transform.parent = m_CachedParent;
                     Debug.LogException(new InvalidParentException($"Invalid parenting, {nameof(NetworkObject)} moved under a non-{nameof(NetworkObject)} parent"));
@@ -709,19 +746,31 @@ namespace Unity.Netcode
             else
             {
                 m_LatestParent = null;
+                removeParent = m_CachedParent != null;
             }
 
-            m_IsReparented = true;
-            ApplyNetworkParenting();
+            ApplyNetworkParenting(removeParent);
 
             var message = new ParentSyncMessage
             {
                 NetworkObjectId = NetworkObjectId,
-                IsReparented = m_IsReparented,
                 IsLatestParentSet = m_LatestParent != null && m_LatestParent.HasValue,
-                LatestParent = m_LatestParent
+                LatestParent = m_LatestParent,
+                RemoveParent = removeParent,
+                WorldPositionStays = m_CachedWorldPositionStays,
+                Position = m_CachedWorldPositionStays ? transform.position : transform.localPosition,
+                Rotation = m_CachedWorldPositionStays ? transform.rotation : transform.localRotation,
+                Scale = transform.localScale,
             };
 
+            // We need to preserve the m_CachedWorldPositionStays value until after we create the message
+            // in order to assure any local space values changed/reset get applied properly. If our
+            // parent is null then go ahead and reset the m_CachedWorldPositionStays the default value.
+            if (parentTransform == null)
+            {
+                m_CachedWorldPositionStays = true;
+            }
+
             unsafe
             {
                 var maxCount = NetworkManager.ConnectedClientsIds.Count;
@@ -749,42 +798,96 @@ namespace Unity.Netcode
         // we call CheckOrphanChildren() method and quickly iterate over OrphanChildren set and see if we can reparent/adopt one.
         internal static HashSet<NetworkObject> OrphanChildren = new HashSet<NetworkObject>();
 
-        internal bool ApplyNetworkParenting()
+        internal bool ApplyNetworkParenting(bool removeParent = false, bool ignoreNotSpawned = false)
         {
             if (!AutoObjectParentSync)
             {
                 return false;
             }
 
-            if (!IsSpawned)
+            // SPECIAL CASE:
+            // The ignoreNotSpawned 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. This is the only scenario where the ignoreNotSpawned parameter is used.
+            if (!IsSpawned && !ignoreNotSpawned)
             {
                 return false;
             }
 
-            if (!m_IsReparented)
+            // Handle the first in-scene placed NetworkObject parenting scenarios. Once the m_LatestParent
+            // has been set, this will not be entered into again (i.e. the later code will be invoked and
+            // users will get notifications when the parent changes).
+            var isInScenePlaced = IsSceneObject.HasValue && IsSceneObject.Value;
+            if (transform.parent != null && !removeParent && !m_LatestParent.HasValue && isInScenePlaced)
             {
-                return true;
+                var parentNetworkObject = transform.parent.GetComponent<NetworkObject>();
+
+                // If parentNetworkObject is null then the parent is a GameObject without a NetworkObject component
+                // attached. Under this case, we preserve the hierarchy but we don't keep track of the parenting.
+                // Note: We only start tracking parenting if the user removes the child from the standard GameObject
+                // parent and then re-parents the child under a GameObject with a NetworkObject component attached.
+                if (parentNetworkObject == null)
+                {
+                    // If we are parented under a GameObject, go ahead and mark the world position stays as false
+                    // so clients synchronize their transform in local space. (only for in-scene placed NetworkObjects)
+                    m_CachedWorldPositionStays = false;
+                    return true;
+                }
+                else // If the parent still isn't spawned add this to the orphaned children and return false
+                if (!parentNetworkObject.IsSpawned)
+                {
+                    OrphanChildren.Add(this);
+                    return false;
+                }
+                else
+                {
+                    // If we made it this far, go ahead and set the network parenting values
+                    // with the WorldPoisitonSays value set to false
+                    // Note: Since in-scene placed NetworkObjects are parented in the scene
+                    // the default "assumption" is that children are parenting local space
+                    // relative.
+                    SetNetworkParenting(parentNetworkObject.NetworkObjectId, false);
+
+                    // Set the cached parent
+                    m_CachedParent = parentNetworkObject.transform;
+
+                    return true;
+                }
             }
 
-            if (m_LatestParent == null || !m_LatestParent.HasValue)
+            // If we are removing the parent or our latest parent is not set, then remove the parent
+            // removeParent is only set when:
+            //  - The server-side NetworkObject.OnTransformParentChanged is invoked and the parent is being removed
+            //  - The client-side when handling a ParentSyncMessage
+            // When clients are synchronizing only the m_LatestParent.HasValue will not have a value if there is no parent
+            // or a parent was removed prior to the client connecting (i.e. in-scene placed NetworkObjects)
+            if (removeParent || !m_LatestParent.HasValue)
             {
                 m_CachedParent = null;
-                transform.parent = null;
-
+                // We must use Transform.SetParent when taking WorldPositionStays into
+                // consideration, otherwise just setting transform.parent = null defaults
+                // to WorldPositionStays which can cause scaling issues if the parent's
+                // scale is not the default (Vetctor3.one) value.
+                transform.SetParent(null, m_CachedWorldPositionStays);
                 InvokeBehaviourOnNetworkObjectParentChanged(null);
                 return true;
             }
 
-            if (!NetworkManager.SpawnManager.SpawnedObjects.ContainsKey(m_LatestParent.Value))
+            // If we have a latest parent id but it hasn't been spawned yet, then add this instance to the orphanChildren
+            // HashSet and return false (i.e. parenting not applied yet)
+            if (m_LatestParent.HasValue && !NetworkManager.SpawnManager.SpawnedObjects.ContainsKey(m_LatestParent.Value))
             {
                 OrphanChildren.Add(this);
                 return false;
             }
 
+            // If we made it here, then parent this instance under the parentObject
             var parentObject = NetworkManager.SpawnManager.SpawnedObjects[m_LatestParent.Value];
 
             m_CachedParent = parentObject.transform;
-            transform.parent = parentObject.transform;
+            transform.SetParent(parentObject.transform, m_CachedWorldPositionStays);
 
             InvokeBehaviourOnNetworkObjectParentChanged(parentObject);
             return true;
@@ -821,6 +924,13 @@ namespace Unity.Netcode
                     Debug.LogWarning($"{ChildNetworkBehaviours[i].gameObject.name} is disabled! Netcode for GameObjects does not support spawning disabled NetworkBehaviours! The {ChildNetworkBehaviours[i].GetType().Name} component was skipped during spawn!");
                 }
             }
+            for (int i = 0; i < ChildNetworkBehaviours.Count; i++)
+            {
+                if (ChildNetworkBehaviours[i].gameObject.activeInHierarchy)
+                {
+                    ChildNetworkBehaviours[i].VisibleOnNetworkSpawn();
+                }
+            }
         }
 
         internal void InvokeBehaviourNetworkDespawn()
@@ -898,13 +1008,17 @@ namespace Unity.Netcode
                 }
             }
         }
-        internal void SetNetworkVariableData(FastBufferReader reader)
+
+        /// <summary>
+        /// Only invoked during first synchronization of a NetworkObject (late join or newly spawned)
+        /// </summary>
+        internal void SetNetworkVariableData(FastBufferReader reader, ulong clientId)
         {
             for (int i = 0; i < ChildNetworkBehaviours.Count; i++)
             {
                 var behaviour = ChildNetworkBehaviours[i];
                 behaviour.InitializeVariables();
-                behaviour.SetNetworkVariableData(reader);
+                behaviour.SetNetworkVariableData(reader, clientId);
             }
         }
 
@@ -941,7 +1055,20 @@ namespace Unity.Netcode
             {
                 if (NetworkLog.CurrentLogLevel <= LogLevel.Error)
                 {
-                    NetworkLog.LogError($"Behaviour index was out of bounds. Did you mess up the order of your {nameof(NetworkBehaviour)}s?");
+                    NetworkLog.LogError($"{nameof(NetworkBehaviour)} index {index} was out of bounds for {name}. NetworkBehaviours must be the same, and in the same order, between server and client.");
+                }
+
+                if (NetworkLog.CurrentLogLevel <= LogLevel.Developer)
+                {
+                    var currentKnownChildren = new System.Text.StringBuilder();
+                    currentKnownChildren.Append($"Known child {nameof(NetworkBehaviour)}s:");
+                    for (int i = 0; i < ChildNetworkBehaviours.Count; i++)
+                    {
+                        var childNetworkBehaviour = ChildNetworkBehaviours[i];
+                        currentKnownChildren.Append($" [{i}] {childNetworkBehaviour.__getTypeName()}");
+                        currentKnownChildren.Append(i < ChildNetworkBehaviours.Count - 1 ? "," : ".");
+                    }
+                    NetworkLog.LogInfo(currentKnownChildren.ToString());
                 }
 
                 return null;
@@ -952,20 +1079,43 @@ namespace Unity.Netcode
 
         internal struct SceneObject
         {
-            public struct HeaderData : INetworkSerializeByMemcpy
-            {
-                public ulong NetworkObjectId;
-                public ulong OwnerClientId;
-                public uint Hash;
+            private byte m_BitField;
+            public uint Hash;
+            public ulong NetworkObjectId;
+            public ulong OwnerClientId;
 
-                public bool IsPlayerObject;
-                public bool HasParent;
-                public bool IsSceneObject;
-                public bool HasTransform;
-                public bool IsReparented;
+            public bool IsPlayerObject
+            {
+                get => ByteUtility.GetBit(m_BitField, 0);
+                set => ByteUtility.SetBit(ref m_BitField, 0, value);
+            }
+            public bool HasParent
+            {
+                get => ByteUtility.GetBit(m_BitField, 1);
+                set => ByteUtility.SetBit(ref m_BitField, 1, value);
+            }
+            public bool IsSceneObject
+            {
+                get => ByteUtility.GetBit(m_BitField, 2);
+                set => ByteUtility.SetBit(ref m_BitField, 2, value);
+            }
+            public bool HasTransform
+            {
+                get => ByteUtility.GetBit(m_BitField, 3);
+                set => ByteUtility.SetBit(ref m_BitField, 3, value);
             }
 
-            public HeaderData Header;
+            public bool IsLatestParentSet
+            {
+                get => ByteUtility.GetBit(m_BitField, 4);
+                set => ByteUtility.SetBit(ref m_BitField, 4, value);
+            }
+
+            public bool WorldPositionStays
+            {
+                get => ByteUtility.GetBit(m_BitField, 5);
+                set => ByteUtility.SetBit(ref m_BitField, 5, value);
+            }
 
             //If(Metadata.HasParent)
             public ulong ParentObjectId;
@@ -975,12 +1125,12 @@ namespace Unity.Netcode
             {
                 public Vector3 Position;
                 public Quaternion Rotation;
+                public Vector3 Scale;
             }
 
             public TransformData Transform;
 
             //If(Metadata.IsReparented)
-            public bool IsLatestParentSet;
 
             //If(IsLatestParentSet)
             public ulong? LatestParent;
@@ -990,98 +1140,170 @@ namespace Unity.Netcode
 
             public int NetworkSceneHandle;
 
-            public unsafe void Serialize(FastBufferWriter writer)
+
+            public void Serialize(FastBufferWriter writer)
             {
-                var writeSize = sizeof(HeaderData);
-                writeSize += Header.HasParent ? FastBufferWriter.GetWriteSize(ParentObjectId) : 0;
-                writeSize += Header.HasTransform ? FastBufferWriter.GetWriteSize(Transform) : 0;
-                writeSize += Header.IsReparented ? FastBufferWriter.GetWriteSize(IsLatestParentSet) + (IsLatestParentSet ? FastBufferWriter.GetWriteSize<ulong>() : 0) : 0;
-                writeSize += Header.IsSceneObject ? FastBufferWriter.GetWriteSize<int>() : 0;
+                writer.WriteValueSafe(m_BitField);
+                writer.WriteValueSafe(Hash);
+                BytePacker.WriteValueBitPacked(writer, NetworkObjectId);
+                BytePacker.WriteValueBitPacked(writer, OwnerClientId);
+
+                if (HasParent)
+                {
+                    BytePacker.WriteValueBitPacked(writer, ParentObjectId);
+                    if (IsLatestParentSet)
+                    {
+                        BytePacker.WriteValueBitPacked(writer, LatestParent.Value);
+                    }
+                }
+
+                var writeSize = 0;
+                writeSize += HasTransform ? FastBufferWriter.GetWriteSize<TransformData>() : 0;
+                writeSize += IsSceneObject ? FastBufferWriter.GetWriteSize<int>() : 0;
 
                 if (!writer.TryBeginWrite(writeSize))
                 {
                     throw new OverflowException("Could not serialize SceneObject: Out of buffer space.");
                 }
 
-                writer.WriteValue(Header);
-
-                if (Header.HasParent)
-                {
-                    writer.WriteValue(ParentObjectId);
-                }
-
-                if (Header.HasTransform)
+                if (HasTransform)
                 {
                     writer.WriteValue(Transform);
                 }
 
-                if (Header.IsReparented)
-                {
-                    writer.WriteValue(IsLatestParentSet);
-                    if (IsLatestParentSet)
-                    {
-                        writer.WriteValue((ulong)LatestParent);
-                    }
-                }
-
                 // In-Scene NetworkObjects are uniquely identified NetworkPrefabs defined by their
-                // NetworkSceneHandle and GlobalObjectIdHash. Since each loaded scene has a unique
-                // handle, it provides us with a unique and persistent "scene prefab asset" instance.
-                // This is only set on in-scene placed NetworkObjects to reduce the over-all packet
-                // sizes for dynamically spawned NetworkObjects.
-                if (Header.IsSceneObject)
+                // NetworkSceneHandle and GlobalObjectIdHash. Client-side NetworkSceneManagers use
+                // this to locate their local instance of the in-scene placed NetworkObject instance.
+                // Only written for in-scene placed NetworkObjects.
+                if (IsSceneObject)
                 {
                     writer.WriteValue(OwnerObject.GetSceneOriginHandle());
                 }
 
-                OwnerObject.WriteNetworkVariableData(writer, TargetClientId);
+                // Synchronize NetworkVariables and NetworkBehaviours
+                var bufferSerializer = new BufferSerializer<BufferSerializerWriter>(new BufferSerializerWriter(writer));
+                OwnerObject.SynchronizeNetworkBehaviours(ref bufferSerializer, TargetClientId);
             }
 
-            public unsafe void Deserialize(FastBufferReader reader)
+            public void Deserialize(FastBufferReader reader)
             {
-                if (!reader.TryBeginRead(sizeof(HeaderData)))
-                {
-                    throw new OverflowException("Could not deserialize SceneObject: Out of buffer space.");
-                }
-                reader.ReadValue(out Header);
-                var readSize = Header.HasParent ? FastBufferWriter.GetWriteSize(ParentObjectId) : 0;
-                readSize += Header.HasTransform ? FastBufferWriter.GetWriteSize(Transform) : 0;
-                readSize += Header.IsReparented ? FastBufferWriter.GetWriteSize(IsLatestParentSet) + (IsLatestParentSet ? FastBufferWriter.GetWriteSize<ulong>() : 0) : 0;
-                readSize += Header.IsSceneObject ? FastBufferWriter.GetWriteSize<int>() : 0;
+                reader.ReadValueSafe(out m_BitField);
+                reader.ReadValueSafe(out Hash);
+                ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
+                ByteUnpacker.ReadValueBitPacked(reader, out OwnerClientId);
 
-                if (!reader.TryBeginRead(readSize))
+                if (HasParent)
                 {
-                    throw new OverflowException("Could not deserialize SceneObject: Out of buffer space.");
-                }
-
-                if (Header.HasParent)
-                {
-                    reader.ReadValue(out ParentObjectId);
-                }
-
-                if (Header.HasTransform)
-                {
-                    reader.ReadValue(out Transform);
-                }
-
-                if (Header.IsReparented)
-                {
-                    reader.ReadValue(out IsLatestParentSet);
+                    ByteUnpacker.ReadValueBitPacked(reader, out ParentObjectId);
                     if (IsLatestParentSet)
                     {
-                        reader.ReadValueSafe(out ulong latestParent);
+                        ByteUnpacker.ReadValueBitPacked(reader, out ulong latestParent);
                         LatestParent = latestParent;
                     }
                 }
 
-                // In-Scene NetworkObjects are uniquely identified NetworkPrefabs defined by their
-                // NetworkSceneHandle and GlobalObjectIdHash. Since each loaded scene has a unique
-                // handle, it provides us with a unique and persistent "scene prefab asset" instance.
-                // Client-side NetworkSceneManagers use this to locate their local instance of the
-                // NetworkObject instance.
-                if (Header.IsSceneObject)
+                var readSize = 0;
+                readSize += HasTransform ? FastBufferWriter.GetWriteSize<TransformData>() : 0;
+                readSize += IsSceneObject ? FastBufferWriter.GetWriteSize<int>() : 0;
+
+                // Try to begin reading the remaining bytes
+                if (!reader.TryBeginRead(readSize))
                 {
-                    reader.ReadValueSafe(out NetworkSceneHandle);
+                    throw new OverflowException("Could not deserialize SceneObject: Reading past the end of the buffer");
+                }
+
+                if (HasTransform)
+                {
+                    reader.ReadValue(out Transform);
+                }
+
+                // In-Scene NetworkObjects are uniquely identified NetworkPrefabs defined by their
+                // NetworkSceneHandle and GlobalObjectIdHash. Client-side NetworkSceneManagers use
+                // this to locate their local instance of the in-scene placed NetworkObject instance.
+                // Only read for in-scene placed NetworkObjects
+                if (IsSceneObject)
+                {
+                    reader.ReadValue(out NetworkSceneHandle);
+                }
+            }
+        }
+
+        internal void PostNetworkVariableWrite()
+        {
+            for (int k = 0; k < ChildNetworkBehaviours.Count; k++)
+            {
+                ChildNetworkBehaviours[k].PostNetworkVariableWrite();
+            }
+        }
+
+        /// <summary>
+        /// Handles synchronizing NetworkVariables and custom synchronization data for NetworkBehaviours.
+        /// </summary>
+        /// <remarks>
+        /// This is where we determine how much data is written after the associated NetworkObject in order to recover
+        /// from a failed instantiated NetworkObject without completely disrupting client synchronization.
+        /// </remarks>
+        internal void SynchronizeNetworkBehaviours<T>(ref BufferSerializer<T> serializer, ulong targetClientId = 0) where T : IReaderWriter
+        {
+            if (serializer.IsWriter)
+            {
+                var writer = serializer.GetFastBufferWriter();
+                var positionBeforeSynchronizing = writer.Position;
+                writer.WriteValueSafe((ushort)0);
+                var sizeToSkipCalculationPosition = writer.Position;
+
+                // Synchronize NetworkVariables
+                WriteNetworkVariableData(writer, targetClientId);
+                // Reserve the NetworkBehaviour synchronization count position
+                var networkBehaviourCountPosition = writer.Position;
+                writer.WriteValueSafe((byte)0);
+
+                // Parse through all NetworkBehaviours and any that return true
+                // had additional synchronization data written.
+                // (See notes for reading/deserialization below)
+                var synchronizationCount = (byte)0;
+                foreach (var childBehaviour in ChildNetworkBehaviours)
+                {
+                    if (childBehaviour.Synchronize(ref serializer))
+                    {
+                        synchronizationCount++;
+                    }
+                }
+
+                var currentPosition = writer.Position;
+                // Write the total number of bytes written for NetworkVariable and NetworkBehaviour
+                // synchronization.
+                writer.Seek(positionBeforeSynchronizing);
+                // We want the size of everything after our size to skip calculation position
+                var size = (ushort)(currentPosition - sizeToSkipCalculationPosition);
+                writer.WriteValueSafe(size);
+                // Write the number of NetworkBehaviours synchronized
+                writer.Seek(networkBehaviourCountPosition);
+                writer.WriteValueSafe(synchronizationCount);
+                // seek back to the position after writing NetworkVariable and NetworkBehaviour
+                // synchronization data.
+                writer.Seek(currentPosition);
+            }
+            else
+            {
+                var reader = serializer.GetFastBufferReader();
+
+                reader.ReadValueSafe(out ushort sizeOfSynchronizationData);
+                var seekToEndOfSynchData = reader.Position + sizeOfSynchronizationData;
+                // Apply the network variable synchronization data
+                SetNetworkVariableData(reader, targetClientId);
+                // Read the number of NetworkBehaviours to synchronize
+                reader.ReadValueSafe(out byte numberSynchronized);
+                var networkBehaviourId = (ushort)0;
+
+                // If a NetworkBehaviour writes synchronization data, it will first
+                // write its NetworkBehaviourId so when deserializing the client-side
+                // can find the right NetworkBehaviour to deserialize the synchronization data.
+                for (int i = 0; i < numberSynchronized; i++)
+                {
+                    serializer.SerializeValue(ref networkBehaviourId);
+                    var networkBehaviour = GetNetworkBehaviourAtOrderIndex(networkBehaviourId);
+                    networkBehaviour.Synchronize(ref serializer);
                 }
             }
         }
@@ -1090,14 +1312,11 @@ namespace Unity.Netcode
         {
             var obj = new SceneObject
             {
-                Header = new SceneObject.HeaderData
-                {
-                    IsPlayerObject = IsPlayerObject,
-                    NetworkObjectId = NetworkObjectId,
-                    OwnerClientId = OwnerClientId,
-                    IsSceneObject = IsSceneObject ?? true,
-                    Hash = HostCheckForGlobalObjectIdHashOverride(),
-                },
+                NetworkObjectId = NetworkObjectId,
+                OwnerClientId = OwnerClientId,
+                IsPlayerObject = IsPlayerObject,
+                IsSceneObject = IsSceneObject ?? true,
+                Hash = HostCheckForGlobalObjectIdHashOverride(),
                 OwnerObject = this,
                 TargetClientId = targetClientId
             };
@@ -1107,27 +1326,21 @@ namespace Unity.Netcode
             if (!AlwaysReplicateAsRoot && transform.parent != null)
             {
                 parentNetworkObject = transform.parent.GetComponent<NetworkObject>();
-            }
-
-            if (parentNetworkObject)
-            {
-                obj.Header.HasParent = true;
-                obj.ParentObjectId = parentNetworkObject.NetworkObjectId;
-            }
-            if (IncludeTransformWhenSpawning == null || IncludeTransformWhenSpawning(OwnerClientId))
-            {
-                obj.Header.HasTransform = true;
-                obj.Transform = new SceneObject.TransformData
+                // In-scene placed NetworkObjects parented under GameObjects with no NetworkObject
+                // should set the has parent flag and preserve the world position stays value
+                if (parentNetworkObject == null && obj.IsSceneObject)
                 {
-                    Position = transform.position,
-                    Rotation = transform.rotation
-                };
+                    obj.HasParent = true;
+                    obj.WorldPositionStays = m_CachedWorldPositionStays;
+                }
             }
 
-            var (isReparented, latestParent) = GetNetworkParenting();
-            obj.Header.IsReparented = isReparented;
-            if (isReparented)
+            if (parentNetworkObject != null)
             {
+                obj.HasParent = true;
+                obj.ParentObjectId = parentNetworkObject.NetworkObjectId;
+                obj.WorldPositionStays = m_CachedWorldPositionStays;
+                var latestParent = GetNetworkParenting();
                 var isLatestParentSet = latestParent != null && latestParent.HasValue;
                 obj.IsLatestParentSet = isLatestParentSet;
                 if (isLatestParentSet)
@@ -1136,6 +1349,43 @@ namespace Unity.Netcode
                 }
             }
 
+            if (IncludeTransformWhenSpawning == null || IncludeTransformWhenSpawning(OwnerClientId))
+            {
+                obj.HasTransform = true;
+
+                // We start with the default AutoObjectParentSync values to determine which transform space we will
+                // be synchronizing clients with.
+                var syncRotationPositionLocalSpaceRelative = obj.HasParent && !m_CachedWorldPositionStays;
+                var syncScaleLocalSpaceRelative = obj.HasParent && !m_CachedWorldPositionStays;
+
+                // If auto object synchronization is turned off
+                if (!AutoObjectParentSync)
+                {
+                    // We always synchronize position and rotation world space relative
+                    syncRotationPositionLocalSpaceRelative = false;
+                    // Scale is special, it synchronizes local space relative if it has a
+                    // parent since applying the world space scale under a parent with scale
+                    // will result in the improper scale for the child
+                    syncScaleLocalSpaceRelative = obj.HasParent;
+                }
+
+
+                obj.Transform = new SceneObject.TransformData
+                {
+                    // If we are parented and we have the m_CachedWorldPositionStays disabled, then use local space
+                    // values as opposed world space values.
+                    Position = syncRotationPositionLocalSpaceRelative ? transform.localPosition : transform.position,
+                    Rotation = syncRotationPositionLocalSpaceRelative ? transform.localRotation : transform.rotation,
+
+                    // We only use the lossyScale if the NetworkObject has a parent. Multi-generation nested children scales can
+                    // impact the final scale of the child NetworkObject in question. The solution is to use the lossy scale
+                    // which can be thought of as "world space scale".
+                    // More information:
+                    // https://docs.unity3d.com/ScriptReference/Transform-lossyScale.html
+                    Scale = syncScaleLocalSpaceRelative ? transform.localScale : transform.lossyScale,
+                };
+            }
+
             return obj;
         }
 
@@ -1144,54 +1394,47 @@ namespace Unity.Netcode
         /// when the client is approved or during a scene transition
         /// </summary>
         /// <param name="sceneObject">Deserialized scene object data</param>
-        /// <param name="variableData">reader for the NetworkVariable data</param>
+        /// <param name="reader">FastBufferReader for the NetworkVariable data</param>
         /// <param name="networkManager">NetworkManager instance</param>
         /// <returns>optional to use NetworkObject deserialized</returns>
-        internal static NetworkObject AddSceneObject(in SceneObject sceneObject, FastBufferReader variableData, NetworkManager networkManager)
+        internal static NetworkObject AddSceneObject(in SceneObject sceneObject, FastBufferReader reader, NetworkManager networkManager)
         {
-            Vector3? position = null;
-            Quaternion? rotation = null;
-            ulong? parentNetworkId = null;
-            int? networkSceneHandle = null;
-
-            if (sceneObject.Header.HasTransform)
-            {
-                position = sceneObject.Transform.Position;
-                rotation = sceneObject.Transform.Rotation;
-            }
-
-            if (sceneObject.Header.HasParent)
-            {
-                parentNetworkId = sceneObject.ParentObjectId;
-            }
-
-            if (sceneObject.Header.IsSceneObject)
-            {
-                networkSceneHandle = sceneObject.NetworkSceneHandle;
-            }
-
             //Attempt to create a local NetworkObject
-            var networkObject = networkManager.SpawnManager.CreateLocalNetworkObject(
-                sceneObject.Header.IsSceneObject, sceneObject.Header.Hash,
-                sceneObject.Header.OwnerClientId, parentNetworkId, networkSceneHandle, position, rotation, sceneObject.Header.IsReparented);
-
-            networkObject?.SetNetworkParenting(sceneObject.Header.IsReparented, sceneObject.LatestParent);
+            var networkObject = networkManager.SpawnManager.CreateLocalNetworkObject(sceneObject);
 
             if (networkObject == null)
             {
                 // Log the error that the NetworkObject failed to construct
-                Debug.LogError($"Failed to spawn {nameof(NetworkObject)} for Hash {sceneObject.Header.Hash}.");
+                if (networkManager.LogLevel <= LogLevel.Normal)
+                {
+                    NetworkLog.LogError($"Failed to spawn {nameof(NetworkObject)} for Hash {sceneObject.Hash}.");
+                }
 
-                // If we failed to load this NetworkObject, then skip past the network variable data
-                variableData.ReadValueSafe(out ushort varSize);
-                variableData.Seek(variableData.Position + varSize);
+                try
+                {
+                    // If we failed to load this NetworkObject, then skip past the Network Variable and (if any) synchronization data
+                    reader.ReadValueSafe(out ushort networkBehaviourSynchronizationDataLength);
+                    reader.Seek(reader.Position + networkBehaviourSynchronizationDataLength);
+                }
+                catch (Exception ex)
+                {
+                    Debug.LogException(ex);
+                }
 
                 // We have nothing left to do here.
                 return null;
             }
 
-            // Spawn the NetworkObject(
-            networkManager.SpawnManager.SpawnNetworkObjectLocally(networkObject, sceneObject, variableData, false);
+            // This will get set again when the NetworkObject is spawned locally, but we set it here ahead of spawning
+            // in order to be able to determine which NetworkVariables the client will be allowed to read.
+            networkObject.OwnerClientId = sceneObject.OwnerClientId;
+
+            // Synchronize NetworkBehaviours
+            var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(reader));
+            networkObject.SynchronizeNetworkBehaviours(ref bufferSerializer, networkManager.LocalClientId);
+
+            // Spawn the NetworkObject
+            networkManager.SpawnManager.SpawnNetworkObjectLocally(networkObject, sceneObject, false);
 
             return networkObject;
         }

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/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
@@ -220,6 +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
             {
@@ -251,7 +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;
@@ -264,6 +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);
-        bool Deserialize(FastBufferReader reader, ref NetworkContext context);
+        void Serialize(FastBufferWriter writer, int targetVersion);
+        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);
-            reader.ReadValue(out NetworkTick);
+                // 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(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);
-            writer.WriteValue(NetworkBehaviourIndex);
+            BytePacker.WriteValueBitPacked(writer, NetworkObjectId);
+            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)))
-            {
-                throw new OverflowException($"Not enough data in the buffer to read {nameof(NetworkVariableDeltaMessage)}");
-            }
-
-            reader.ReadValue(out NetworkObjectId);
-            reader.ReadValue(out NetworkBehaviourIndex);
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkBehaviourIndex);
 
             m_ReceivedNetworkVariableData = reader;
 

Runtime/Messaging/Messages/OrderingMessage.cs

@@ -1,50 +0,0 @@
-using System;
-
-namespace Unity.Netcode
-{
-    /// <summary>
-    /// Upon connecting, the host sends a series of OrderingMessage to the client so that it can make sure both sides
-    /// have the same message types in the same positions in
-    /// - MessagingSystem.m_MessageHandlers
-    /// - MessagingSystem.m_ReverseTypeMap
-    /// even if one side has extra messages (compilation, version, patch, or platform differences, etc...)
-    ///
-    /// The ConnectionRequestedMessage, ConnectionApprovedMessage and OrderingMessage are prioritized at the beginning
-    /// of the mapping, to guarantee they can be exchanged before the two sides share their ordering
-    /// The sorting used in also stable so that even if MessageType names share hashes, it will work most of the time
-    /// </summary>
-    internal struct OrderingMessage : INetworkMessage
-    {
-        public int Order;
-        public uint Hash;
-
-        public void Serialize(FastBufferWriter writer)
-        {
-            if (!writer.TryBeginWrite(FastBufferWriter.GetWriteSize(Order) + FastBufferWriter.GetWriteSize(Hash)))
-            {
-                throw new OverflowException($"Not enough space in the buffer to write {nameof(OrderingMessage)}");
-            }
-
-            writer.WriteValue(Order);
-            writer.WriteValue(Hash);
-        }
-
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
-        {
-            if (!reader.TryBeginRead(FastBufferWriter.GetWriteSize(Order) + FastBufferWriter.GetWriteSize(Hash)))
-            {
-                throw new OverflowException($"Not enough data in the buffer to read {nameof(OrderingMessage)}");
-            }
-
-            reader.ReadValue(out Order);
-            reader.ReadValue(out Hash);
-
-            return true;
-        }
-
-        public void Handle(ref NetworkContext context)
-        {
-            ((NetworkManager)context.SystemOwner).MessagingSystem.ReorderMessage(Order, Hash);
-        }
-    }
-}

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);
-            writer.WriteValueSafe(IsReparented);
-            if (IsReparented)
-            {
-                writer.WriteValueSafe(IsLatestParentSet);
-                if (IsLatestParentSet)
-                {
-                    writer.WriteValueSafe((ulong)LatestParent);
-                }
-            }
+            get => ByteUtility.GetBit(m_BitField, 2);
+            set => ByteUtility.SetBit(ref m_BitField, 2, value);
         }
 
-        public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+        // 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)
+            {
+                if (IsLatestParentSet)
+                {
+                    BytePacker.WriteValueBitPacked(writer, LatestParent.Value);
+                }
+            }
+
+            // 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);
-            reader.ReadValueSafe(out IsReparented);
-            if (IsReparented)
+            ByteUnpacker.ReadValueBitPacked(reader, out NetworkObjectId);
+            reader.ReadValueSafe(out m_BitField);
+            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.ApplyNetworkParenting();
+            networkObject.SetNetworkParenting(LatestParent, WorldPositionStays);
+            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))
-            {
-                throw new OverflowException("Not enough space in the buffer to store RPC data.");
-            }
-
-            writer.WriteValue(metadata);
-            writer.WriteBytes(payload.GetUnsafePtr(), payload.Length);
+            BytePacker.WriteValueBitPacked(writer, metadata.NetworkObjectId);
+            BytePacker.WriteValueBitPacked(writer, metadata.NetworkBehaviourId);
+            BytePacker.WriteValueBitPacked(writer, metadata.NetworkRpcMethodId);
+            writer.WriteBytesSafe(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>();
-            if (!reader.TryBeginRead(metadataSize))
-            {
-                throw new InvalidOperationException("Not enough data in the buffer to read RPC meta.");
-            }
-
-            reader.ReadValue(out metadata);
+            ByteUnpacker.ReadValueBitPacked(reader, out metadata.NetworkObjectId);
+            ByteUnpacker.ReadValueBitPacked(reader, out metadata.NetworkBehaviourId);
+            ByteUnpacker.ReadValueBitPacked(reader, out metadata.NetworkRpcMethodId);
 
             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

@@ -46,6 +46,7 @@ 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);
 
@@ -56,6 +57,11 @@ namespace Unity.Netcode
         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;
@@ -74,12 +80,13 @@ 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)
@@ -90,9 +97,8 @@ namespace Unity.Netcode
             // 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 == "Unity.Netcode.ConnectionRequestMessage" ||
-                    t.MessageType.FullName == "Unity.Netcode.ConnectionApprovedMessage" ||
-                    t.MessageType.FullName == "Unity.Netcode.OrderingMessage")
+                if (t.MessageType.FullName == typeof(ConnectionRequestMessage).FullName ||
+                    t.MessageType.FullName == typeof(ConnectionApprovedMessage).FullName)
                 {
                     prioritizedTypes.Add(t);
                 }
@@ -100,9 +106,8 @@ namespace Unity.Netcode
 
             foreach (var t in allowedTypes)
             {
-                if (t.MessageType.FullName != "Unity.Netcode.ConnectionRequestMessage" &&
-                    t.MessageType.FullName != "Unity.Netcode.ConnectionApprovedMessage" &&
-                    t.MessageType.FullName != "Unity.Netcode.OrderingMessage")
+                if (t.MessageType.FullName != typeof(ConnectionRequestMessage).FullName &&
+                    t.MessageType.FullName != typeof(ConnectionApprovedMessage).FullName)
                 {
                     prioritizedTypes.Add(t);
                 }
@@ -189,7 +194,14 @@ namespace Unity.Netcode
 
             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)
@@ -270,68 +282,53 @@ namespace Unity.Netcode
             return true;
         }
 
-        // Moves the handler for the type having hash `targetHash` to the `desiredOrder` position, in the handler list
-        // This allows the server to tell the client which id it is using for which message and make sure the right
-        // message is used when deserializing.
-        internal void ReorderMessage(int desiredOrder, uint targetHash)
+        internal Type GetMessageForHash(uint messageHash)
         {
-            if (desiredOrder < 0)
+            if (!m_MessagesByHash.ContainsKey(messageHash))
             {
-                throw new ArgumentException("ReorderMessage desiredOrder must be positive");
+                return null;
             }
+            return m_MessagesByHash[messageHash];
+        }
 
-            if (desiredOrder < m_ReverseTypeMap.Length &&
-                XXHash.Hash32(m_ReverseTypeMap[desiredOrder].FullName) == targetHash)
+        internal void SetVersion(ulong clientId, uint messageHash, int version)
+        {
+            if (!m_MessagesByHash.ContainsKey(messageHash))
             {
-                // matching positions and hashes. All good.
                 return;
             }
+            var messageType = m_MessagesByHash[messageHash];
 
-            Debug.Log($"Unexpected hash for {desiredOrder}");
-
-            // Since the message at `desiredOrder` is not the expected one,
-            // insert an empty placeholder and move the messages down
-            var typesAsList = new List<Type>(m_ReverseTypeMap);
-
-            typesAsList.Insert(desiredOrder, null);
-            var handlersAsList = new List<MessageHandler>(m_MessageHandlers);
-            handlersAsList.Insert(desiredOrder, null);
-
-            // we added a dummy message, bump the end up
-            m_HighMessageType++;
-
-            // Here, we rely on the server telling us about all messages, in order.
-            // So, we know the handlers before desiredOrder are correct.
-            // We start at desiredOrder to not shift them when we insert.
-            int position = desiredOrder;
-            bool found = false;
-            while (position < typesAsList.Count)
+            if (!m_PerClientMessageVersions.ContainsKey(clientId))
             {
-                if (typesAsList[position] != null &&
-                    XXHash.Hash32(typesAsList[position].FullName) == targetHash)
+                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]))
                 {
-                    found = true;
-                    break;
+                    continue;
                 }
-
-                position++;
+                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;
             }
-
-            if (found)
-            {
-                // Copy the handler and type to the right index
-
-                typesAsList[desiredOrder] = typesAsList[position];
-                handlersAsList[desiredOrder] = handlersAsList[position];
-                typesAsList.RemoveAt(position);
-                handlersAsList.RemoveAt(position);
-
-                // we removed a copy after moving a message, reduce the high message index
-                m_HighMessageType--;
-            }
-
-            m_ReverseTypeMap = typesAsList.ToArray();
-            m_MessageHandlers = handlersAsList.ToArray();
         }
 
         public void HandleMessage(in MessageHeader header, FastBufferReader reader, ulong senderId, float timestamp, int serializedHeaderSize)
@@ -433,7 +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)
@@ -444,10 +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)
                 {
@@ -485,16 +539,47 @@ namespace Unity.Netcode
                 return 0;
             }
 
-            var maxSize = delivery == NetworkDelivery.ReliableFragmentedSequenced ? FRAGMENTED_MESSAGE_MAX_SIZE : NON_FRAGMENTED_MESSAGE_MAX_SIZE;
+            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;
+                    }
+                }
 
-            using var tmpSerializer = new FastBufferWriter(NON_FRAGMENTED_MESSAGE_MAX_SIZE - FastBufferWriter.GetWriteSize<MessageHeader>(), Allocator.Temp, maxSize - FastBufferWriter.GetWriteSize<MessageHeader>());
+                if (sentMessageVersions.Contains(messageVersion))
+                {
+                    continue;
+                }
 
-            message.Serialize(tmpSerializer);
+                sentMessageVersions.Add(messageVersion);
 
-            return SendPreSerializedMessage(tmpSerializer, maxSize, ref message, delivery, clientIds);
+                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, messageVersion);
+
+                var size = SendPreSerializedMessage(tmpSerializer, maxSize, ref message, delivery, clientIds, messageVersion);
+                largestSerializedSize = size > largestSerializedSize ? size : largestSerializedSize;
+            }
+
+            sentMessageVersions.Dispose();
+
+            return largestSerializedSize;
         }
 
-        internal unsafe int SendPreSerializedMessage<TMessageType>(in FastBufferWriter tmpSerializer, int maxSize, ref TMessageType message, NetworkDelivery delivery, in IReadOnlyList<ulong> clientIds)
+        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);
@@ -509,6 +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))
@@ -559,8 +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/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;
-
-        static Dictionary<uint, string> s_SceneEventTypeNames;
-
-        static ProfilerMarker s_FrameDispatch = new ProfilerMarker($"{nameof(NetworkMetrics)}.DispatchFrame");
+        private const ulong k_MaxMetricsPerFrame = 1000L;
+        private static Dictionary<uint, string> s_SceneEventTypeNames;
+        private static ProfilerMarker s_FrameDispatch = new ProfilerMarker($"{nameof(NetworkMetrics)}.DispatchFrame");
 
         static NetworkMetrics()
         {
@@ -531,7 +528,7 @@ namespace Unity.Netcode
         }
     }
 
-        internal class NetcodeObserver
+    internal class NetcodeObserver
     {
         public static IMetricObserver Observer { get; } = MetricObserverFactory.Construct();
     }

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;
 
@@ -15,7 +15,7 @@ namespace Unity.Netcode
 
         public Object GetNetworkObject(ulong networkObjectId)
         {
-            if(m_NetworkManager.SpawnManager.SpawnedObjects.TryGetValue(networkObjectId, out NetworkObject value))
+            if (m_NetworkManager.SpawnManager.SpawnedObjects.TryGetValue(networkObjectId, out NetworkObject value))
             {
                 return value;
             }

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>
@@ -39,9 +39,13 @@ namespace Unity.Netcode
             NetworkVariableWritePermission writePerm = DefaultWritePerm)
             : base(readPerm, writePerm)
         {
-            foreach (var value in values)
+            // allow null IEnumerable<T> to mean "no values"
+            if (values != null)
             {
-                m_List.Add(value);
+                foreach (var value in values)
+                {
+                    m_List.Add(value);
+                }
             }
         }
 
@@ -52,7 +56,6 @@ namespace Unity.Netcode
             if (m_DirtyEvents.Length > 0)
             {
                 m_DirtyEvents.Clear();
-                m_ListAtLastReset.CopyFrom(m_List);
             }
         }
 
@@ -65,6 +68,13 @@ namespace Unity.Netcode
 
         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);
         }
 
@@ -127,26 +137,10 @@ namespace Unity.Netcode
         /// <inheritdoc />
         public override void WriteField(FastBufferWriter writer)
         {
-            // The listAtLastReset mechanism was put in place to deal with duplicate adds
-            // upon initial spawn. However, it causes issues with in-scene placed objects
-            // due to difference in spawn order. In order to address this, we pick the right
-            // list based on the type of object.
-            bool isSceneObject = m_NetworkBehaviour.NetworkObject.IsSceneObject != false;
-            if (isSceneObject)
+            writer.WriteValueSafe((ushort)m_List.Length);
+            for (int i = 0; i < m_List.Length; i++)
             {
-                writer.WriteValueSafe((ushort)m_ListAtLastReset.Length);
-                for (int i = 0; i < m_ListAtLastReset.Length; i++)
-                {
-                    NetworkVariableSerialization<T>.Write(writer, ref m_ListAtLastReset.ElementAt(i));
-                }
-            }
-            else
-            {
-                writer.WriteValueSafe((ushort)m_List.Length);
-                for (int i = 0; i < m_List.Length; i++)
-                {
-                    NetworkVariableSerialization<T>.Write(writer, ref m_List.ElementAt(i));
-                }
+                NetworkVariableSerialization<T>.Write(writer, ref m_List.ElementAt(i));
             }
         }
 
@@ -157,7 +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);
             }
         }
@@ -173,7 +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)
@@ -201,7 +197,8 @@ namespace Unity.Netcode
                     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)
                             {
@@ -237,7 +234,8 @@ namespace Unity.Netcode
                         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)
                             {
@@ -299,7 +297,8 @@ namespace Unity.Netcode
                     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");
@@ -374,6 +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>()
@@ -389,6 +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>()
@@ -402,14 +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;
@@ -438,6 +455,12 @@ 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);
@@ -461,6 +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>()
@@ -478,6 +507,12 @@ 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;
 
@@ -520,7 +555,6 @@ namespace Unity.Netcode
         public override void Dispose()
         {
             m_List.Dispose();
-            m_ListAtLastReset.Dispose();
             m_DirtyEvents.Dispose();
         }
     }

Runtime/NetworkVariable/NetworkVariable.cs

@@ -1,7 +1,5 @@
 using UnityEngine;
 using System;
-using System.Runtime.CompilerServices;
-using Unity.Collections.LowLevel.Unsafe;
 
 namespace Unity.Netcode
 {
@@ -10,7 +8,7 @@ namespace Unity.Netcode
     /// </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
@@ -52,7 +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;
                 }
@@ -66,20 +64,6 @@ namespace Unity.Netcode
             }
         }
 
-        // Compares two values of the same unmanaged type by underlying memory
-        // Ignoring any overridden value checks
-        // Size is fixed
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe bool ValueEquals(ref T a, ref T b)
-        {
-            // 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;
-        }
-
         /// <summary>
         /// Sets the <see cref="Value"/>, marks the <see cref="NetworkVariable{T}"/> dirty, and invokes the <see cref="OnValueChanged"/> callback
         /// if there are subscribers to that event.
@@ -115,7 +99,7 @@ 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)
             {
@@ -128,7 +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
 {
@@ -79,8 +80,15 @@ namespace Unity.Netcode
         public virtual void SetDirty(bool isDirty)
         {
             m_IsDirty = isDirty;
-            if (m_IsDirty && m_NetworkBehaviour != null)
+
+            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);
             }
         }

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,
-    /// 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.
+    /// Serializer for FixedStrings
     /// </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);
-        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)
+        public void Write(FastBufferWriter writer, ref T value)
         {
-            int length = GetLength(ref value);
-            byte* data = GetUnsafePtr(ref value);
-            writer.WriteUnmanagedSafe(length);
-            writer.WriteBytesSafe(data, length);
+            writer.WriteValueSafe(value);
         }
-        public unsafe void Read(FastBufferReader reader, out T value)
+        public void Read(FastBufferReader reader, ref T value)
         {
-            value = new T();
-            reader.ReadValueSafe(out int length);
-            SetLength(ref value, length);
-            reader.ReadBytesSafe(GetUnsafePtr(ref value), length);
+            reader.ReadValueSafeInPlace(ref value);
         }
     }
 
     /// <summary>
-    /// Serializer for INetworkSerializable types, which does the same thing
-    /// 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.
+    /// Serializer for unmanaged INetworkSerializable types
     /// </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)
         {
-            value = new T();
             var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(reader));
-            ReadValue(ref value, bufferSerializer);
+            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();
+                }
+                value.NetworkSerialize(bufferSerializer);
+            }
         }
     }
 
@@ -164,7 +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)
             {
@@ -174,34 +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),
-            typeof(byte),
-            typeof(sbyte),
-            typeof(char),
-            typeof(decimal),
-            typeof(double),
-            typeof(float),
-            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)
-        };
+            NetworkVariableSerialization<short>.Serializer = new ShortSerializer();
+            NetworkVariableSerialization<short>.AreEqual = NetworkVariableSerialization<short>.ValueEquals;
+            NetworkVariableSerialization<ushort>.Serializer = new UshortSerializer();
+            NetworkVariableSerialization<ushort>.AreEqual = NetworkVariableSerialization<ushort>.ValueEquals;
+            NetworkVariableSerialization<int>.Serializer = new IntSerializer();
+            NetworkVariableSerialization<int>.AreEqual = NetworkVariableSerialization<int>.ValueEquals;
+            NetworkVariableSerialization<uint>.Serializer = new UintSerializer();
+            NetworkVariableSerialization<uint>.AreEqual = NetworkVariableSerialization<uint>.ValueEquals;
+            NetworkVariableSerialization<long>.Serializer = new LongSerializer();
+            NetworkVariableSerialization<long>.AreEqual = NetworkVariableSerialization<long>.ValueEquals;
+            NetworkVariableSerialization<ulong>.Serializer = new UlongSerializer();
+            NetworkVariableSerialization<ulong>.AreEqual = NetworkVariableSerialization<ulong>.ValueEquals;
+        }
+
+        /// <summary>
+        /// Registeres an unmanaged type that will be serialized by a direct memcpy into a buffer
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        public static void InitializeSerializer_UnmanagedByMemcpy<T>() where T : unmanaged
+        {
+            NetworkVariableSerialization<T>.Serializer = new UnmanagedTypeSerializer<T>();
+        }
+
+        /// <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>
@@ -212,56 +385,59 @@ namespace Unity.Netcode
     /// </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);
+            var bptr = UnsafeUtility.AddressOf(ref b);
+
+            // compare addresses
+            return UnsafeUtility.MemCmp(aptr, bptr, sizeof(TValueType)) == 0;
+        }
+
+        internal static bool EqualityEqualsObject<TValueType>(ref TValueType a, ref TValueType b) where TValueType : class, IEquatable<TValueType>
+        {
+            if (a == null)
             {
-                return new UnmanagedTypeSerializer<T>();
-            }
-            if (typeof(INetworkSerializeByMemcpy).IsAssignableFrom(typeof(T)))
-            {
-                return new UnmanagedTypeSerializer<T>();
-            }
-            if (typeof(Enum).IsAssignableFrom(typeof(T)))
-            {
-                return new UnmanagedTypeSerializer<T>();
+                return b == null;
             }
 
-            if (typeof(INetworkSerializable).IsAssignableFrom(typeof(T)))
+            if (b == null)
             {
-                // Obtains "Open Instance Delegates" for the type's NetworkSerialize() methods -
-                // one for an instance of the generic method taking BufferSerializerWriter as T,
-                // one for an instance of the generic method taking BufferSerializerReader as T
-                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 };
+                return false;
             }
 
-            if (typeof(IUTF8Bytes).IsAssignableFrom(typeof(T)) && typeof(INativeList<byte>).IsAssignableFrom(typeof(T)))
-            {
-                // Get "OpenInstanceDelegates" for the Length property (get and set, which are prefixed
-                // 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 a.Equals(b);
+        }
 
-            return new FallbackSerializer<T>();
+        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
-        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, SceneEventProgress sceneEventProgress);
 
-        AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, SceneEventAction sceneEventAction);
-
-        AsyncOperation UnloadSceneAsync(Scene scene, SceneEventAction sceneEventAction);
+        AsyncOperation UnloadSceneAsync(Scene scene, SceneEventProgress sceneEventProgress);
     }
 }

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,
-                ClientsThatTimedOut = m_NetworkManager.ConnectedClients.Keys.Except(sceneEventProgress.DoneClients).ToList(),
+                ClientsThatCompleted = clientsThatCompleted,
+                ClientsThatTimedOut = clientsThatTimedOut,
             });
 
             if (sceneEventData.SceneEventType == SceneEventType.LoadEventCompleted)
@@ -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 };
-            var sceneUnload = SceneManagerHandler.UnloadSceneAsync(scene, sceneEventAction);
-
-            // If integration testing, IntegrationTestSceneHandler returns null
-            if (sceneUnload == null)
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneEventAction);
-            }
-            else
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneUnload);
-            }
+            sceneEventProgress.SceneEventId = sceneEventData.SceneEventId;
+            sceneEventProgress.OnSceneEventCompleted = OnSceneUnloaded;
+            var sceneUnload = SceneManagerHandler.UnloadSceneAsync(scene, sceneEventProgress);
 
             // 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 sceneUnload = SceneManagerHandler.UnloadSceneAsync(ScenesLoaded[sceneHandle],
-                new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventData.SceneEventId, EventAction = OnSceneUnloaded });
+            var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
+            sceneEventProgress.SceneEventId = sceneEventData.SceneEventId;
+            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,
-                        new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = EmptySceneUnloadedOperation });
+                    var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
+                    sceneEventProgress.SceneEventId = sceneEventId;
+                    sceneEventProgress.OnSceneEventCompleted = EmptySceneUnloadedOperation;
+                    var sceneUnload = SceneManagerHandler.UnloadSceneAsync(keyHandleEntry.Value, sceneEventProgress);
                     SceneUnloadEventHandler.RegisterScene(this, keyHandleEntry.Value, LoadSceneMode.Additive, sceneUnload);
                 }
             }
@@ -1180,18 +1176,9 @@ namespace Unity.Netcode
             }
 
             // Now start loading the scene
-            var sceneEventAction = new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = OnSceneLoaded };
-            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode, sceneEventAction);
-            // If integration testing, IntegrationTestSceneHandler returns null
-            if (sceneLoad == null)
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneEventAction);
-            }
-            else
-            {
-                sceneEventProgress.SetSceneLoadOperation(sceneLoad);
-            }
-
+            sceneEventProgress.SceneEventId = sceneEventId;
+            sceneEventProgress.OnSceneEventCompleted = OnSceneLoaded;
+            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode, sceneEventProgress);
             // Notify the local server that a scene loading event has begun
             OnSceneEvent?.Invoke(new SceneEvent()
             {
@@ -1355,9 +1342,10 @@ namespace Unity.Netcode
                 SceneUnloadEventHandler.RegisterScene(this, SceneManager.GetActiveScene(), LoadSceneMode.Single);
 
             }
-
-            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, sceneEventData.LoadSceneMode,
-                new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = OnSceneLoaded });
+            var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
+            sceneEventProgress.SceneEventId = sceneEventId;
+            sceneEventProgress.OnSceneEventCompleted = OnSceneLoaded;
+            var sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, sceneEventData.LoadSceneMode, sceneEventProgress);
 
             OnSceneEvent?.Invoke(new SceneEvent()
             {
@@ -1453,6 +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;
 
@@ -1488,7 +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);
         }
@@ -1662,8 +1653,10 @@ namespace Unity.Netcode
             if (!shouldPassThrough)
             {
                 // If not, then load the scene
-                sceneLoad = SceneManagerHandler.LoadSceneAsync(sceneName, loadSceneMode,
-                new ISceneManagerHandler.SceneEventAction() { SceneEventId = sceneEventId, EventAction = ClientLoadedSynchronization });
+                var sceneEventProgress = new SceneEventProgress(m_NetworkManager);
+                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()
@@ -1880,7 +1873,7 @@ namespace Unity.Netcode
 
                         if (SceneEventProgressTracking.ContainsKey(sceneEventData.SceneEventProgressId))
                         {
-                            SceneEventProgressTracking[sceneEventData.SceneEventProgressId].AddClientAsDone(clientId);
+                            SceneEventProgressTracking[sceneEventData.SceneEventProgressId].ClientFinishedSceneEvent(clientId);
                         }
                         EndSceneEvent(sceneEventId);
                         break;
@@ -1889,7 +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()
@@ -2025,7 +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);
-                BytePacker.WriteValuePacked(writer, m_DespawnedInSceneObjectsSync[i].GetSceneOriginHandle());
-                BytePacker.WriteValuePacked(writer, m_DespawnedInSceneObjectsSync[i].GlobalObjectIdHash);
+                writer.WriteValueSafe(m_DespawnedInSceneObjectsSync[i].GetSceneOriginHandle());
+                writer.WriteValueSafe(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)
                 {
@@ -701,6 +767,90 @@ namespace Unity.Netcode
             }
         }
 
+        /// <summary>
+        /// For synchronizing any despawned in-scene placed NetworkObjects that were
+        /// despawned by the server during synchronization or scene loading
+        /// </summary>
+        private void DeserializeDespawnedInScenePlacedNetworkObjects()
+        {
+            // Process all de-spawned in-scene NetworkObjects for this network session
+            m_DespawnedInSceneObjects.Clear();
+            InternalBuffer.ReadValueSafe(out int despawnedObjectsCount);
+            var sceneCache = new Dictionary<int, Dictionary<uint, NetworkObject>>();
+
+            for (int i = 0; i < despawnedObjectsCount; i++)
+            {
+                // We just need to get the scene
+                InternalBuffer.ReadValueSafe(out int networkSceneHandle);
+                InternalBuffer.ReadValueSafe(out uint globalObjectIdHash);
+                var sceneRelativeNetworkObjects = new Dictionary<uint, NetworkObject>();
+                if (!sceneCache.ContainsKey(networkSceneHandle))
+                {
+                    if (m_NetworkManager.SceneManager.ServerSceneHandleToClientSceneHandle.ContainsKey(networkSceneHandle))
+                    {
+                        var localSceneHandle = m_NetworkManager.SceneManager.ServerSceneHandleToClientSceneHandle[networkSceneHandle];
+                        if (m_NetworkManager.SceneManager.ScenesLoaded.ContainsKey(localSceneHandle))
+                        {
+                            var objectRelativeScene = m_NetworkManager.SceneManager.ScenesLoaded[localSceneHandle];
+
+                            // 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);
+                        }
+                        else
+                        {
+                            UnityEngine.Debug.LogError($"In-Scene NetworkObject GlobalObjectIdHash ({globalObjectIdHash}) cannot find its relative local scene handle {localSceneHandle}!");
+                        }
+                    }
+                    else
+                    {
+                        UnityEngine.Debug.LogError($"In-Scene NetworkObject GlobalObjectIdHash ({globalObjectIdHash}) cannot find its relative NetworkSceneHandle {networkSceneHandle}!");
+                    }
+                }
+                else // Use the cached NetworkObjects if they exist
+                {
+                    sceneRelativeNetworkObjects = sceneCache[networkSceneHandle];
+                }
+
+                // Now find the in-scene NetworkObject with the current GlobalObjectIdHash we are looking for
+                if (sceneRelativeNetworkObjects.ContainsKey(globalObjectIdHash))
+                {
+                    // Since this is a NetworkObject that was never spawned, we just need to send a notification
+                    // out that it was despawned so users can make adjustments
+                    sceneRelativeNetworkObjects[globalObjectIdHash].InvokeBehaviourNetworkDespawn();
+                    if (!m_NetworkManager.SceneManager.ScenePlacedObjects.ContainsKey(globalObjectIdHash))
+                    {
+                        m_NetworkManager.SceneManager.ScenePlacedObjects.Add(globalObjectIdHash, new Dictionary<int, NetworkObject>());
+                    }
+
+                    if (!m_NetworkManager.SceneManager.ScenePlacedObjects[globalObjectIdHash].ContainsKey(sceneRelativeNetworkObjects[globalObjectIdHash].GetSceneOriginHandle()))
+                    {
+                        m_NetworkManager.SceneManager.ScenePlacedObjects[globalObjectIdHash].Add(sceneRelativeNetworkObjects[globalObjectIdHash].GetSceneOriginHandle(), sceneRelativeNetworkObjects[globalObjectIdHash]);
+                    }
+                }
+                else
+                {
+                    UnityEngine.Debug.LogError($"In-Scene NetworkObject GlobalObjectIdHash ({globalObjectIdHash}) could not be found!");
+                }
+            }
+        }
+
         /// <summary>
         /// Client Side:
         /// During the processing of a server sent Event_Sync, this method will be called for each scene once
@@ -713,93 +863,32 @@ namespace Unity.Netcode
             try
             {
                 // Process all spawned NetworkObjects for this network session
-                ByteUnpacker.ReadValuePacked(InternalBuffer, out int newObjectsCount);
-
-
+                InternalBuffer.ReadValueSafe(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);
 
+                    // 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 (!m_NetworkObjectsSync.Contains(spawnedNetworkObject))
+
+                    // If we failed to deserialize the NetowrkObject then don't add null to the list
+                    if (spawnedNetworkObject != null)
                     {
-                        m_NetworkObjectsSync.Add(spawnedNetworkObject);
+                        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);
-                var sceneCache = new Dictionary<int, Dictionary<uint, NetworkObject>>();
+                // Now deserialize the despawned in-scene placed NetworkObjects list (if any)
+                DeserializeDespawnedInScenePlacedNetworkObjects();
 
-                for (int i = 0; i < despawnedObjectsCount; i++)
-                {
-                    // We just need to get the scene
-                    ByteUnpacker.ReadValuePacked(InternalBuffer, out int networkSceneHandle);
-                    ByteUnpacker.ReadValuePacked(InternalBuffer, out uint globalObjectIdHash);
-                    var sceneRelativeNetworkObjects = new Dictionary<uint, NetworkObject>();
-                    if (!sceneCache.ContainsKey(networkSceneHandle))
-                    {
-                        if (m_NetworkManager.SceneManager.ServerSceneHandleToClientSceneHandle.ContainsKey(networkSceneHandle))
-                        {
-                            var localSceneHandle = m_NetworkManager.SceneManager.ServerSceneHandleToClientSceneHandle[networkSceneHandle];
-                            if (m_NetworkManager.SceneManager.ScenesLoaded.ContainsKey(localSceneHandle))
-                            {
-                                var objectRelativeScene = m_NetworkManager.SceneManager.ScenesLoaded[localSceneHandle];
-                                var inSceneNetworkObjects = UnityEngine.Object.FindObjectsOfType<NetworkObject>().Where((c) =>
-                                c.GetSceneOriginHandle() == localSceneHandle && (c.IsSceneObject != false)).ToList();
-
-                                foreach (var inSceneObject in inSceneNetworkObjects)
-                                {
-                                    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);
-                            }
-                            else
-                            {
-                                UnityEngine.Debug.LogError($"In-Scene NetworkObject GlobalObjectIdHash ({globalObjectIdHash}) cannot find its relative local scene handle {localSceneHandle}!");
-                            }
-                        }
-                        else
-                        {
-                            UnityEngine.Debug.LogError($"In-Scene NetworkObject GlobalObjectIdHash ({globalObjectIdHash}) cannot find its relative NetworkSceneHandle {networkSceneHandle}!");
-                        }
-                    }
-                    else // Use the cached NetworkObjects if they exist
-                    {
-                        sceneRelativeNetworkObjects = sceneCache[networkSceneHandle];
-                    }
-
-                    // Now find the in-scene NetworkObject with the current GlobalObjectIdHash we are looking for
-                    if (sceneRelativeNetworkObjects.ContainsKey(globalObjectIdHash))
-                    {
-                        // Since this is a NetworkObject that was never spawned, we just need to send a notification
-                        // out that it was despawned so users can make adjustments
-                        sceneRelativeNetworkObjects[globalObjectIdHash].InvokeBehaviourNetworkDespawn();
-                        if (!m_NetworkManager.SceneManager.ScenePlacedObjects.ContainsKey(globalObjectIdHash))
-                        {
-                            m_NetworkManager.SceneManager.ScenePlacedObjects.Add(globalObjectIdHash, new Dictionary<int, NetworkObject>());
-                        }
-
-                        if (!m_NetworkManager.SceneManager.ScenePlacedObjects[globalObjectIdHash].ContainsKey(sceneRelativeNetworkObjects[globalObjectIdHash].GetSceneOriginHandle()))
-                        {
-                            m_NetworkManager.SceneManager.ScenePlacedObjects[globalObjectIdHash].Add(sceneRelativeNetworkObjects[globalObjectIdHash].GetSceneOriginHandle(), sceneRelativeNetworkObjects[globalObjectIdHash]);
-                        }
-
-                    }
-                    else
-                    {
-                        UnityEngine.Debug.LogError($"In-Scene NetworkObject GlobalObjectIdHash ({globalObjectIdHash}) could not be found!");
-                    }
-                }
             }
             finally
             {

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>
-        /// 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; }
+        internal Action<uint> OnSceneEventCompleted;
 
         /// <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;
-                m_TimeOutCoroutine = m_NetworkManager.StartCoroutine(TimeOutSceneEventProgress());
-                TimeAtInitiation = Time.realtimeSinceStartup;
+
+                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());
+                }
             }
             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();
-                if (!IsCompleted)
-                {
-                    TimedOut = TimeAtInitiation - Time.realtimeSinceStartup >= m_NetworkManager.NetworkConfig.LoadSceneTimeOut;
-                }
+                TryFinishingSceneEventProgress();
             }
         }
 
-        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)
-        /// 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)
+        /// Sets the client's scene event progress to finished/true
         /// </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;
-            AreAllClientsDoneLoading = true;
-
-            // If OnComplete is not registered or it is and returns true then remove this from the progress tracking
-            if (OnComplete == null || (OnComplete != null && OnComplete.Invoke(this)))
+            // If the network session is terminated/terminating then finish tracking
+            // this scene event
+            if (!IsNetworkSessionActive())
             {
-                m_NetworkManager.SceneManager.SceneEventProgressTracking.Remove(Guid);
+                return true;
             }
-            m_NetworkManager.StopCoroutine(m_TimeOutCoroutine);
-        }
 
-        internal void CheckCompletion()
-        {
-            try
+            // Clients skip over this
+            foreach (var clientStatus in ClientsProcessingSceneEvent)
             {
-                if ((!IsCompleted && DoneClients.Count == m_NetworkManager.ConnectedClientsList.Count && (m_SceneLoadOperation == null || m_SceneLoadOperation.isDone)) || (!IsCompleted && TimedOut))
+                if (!clientStatus.Value)
                 {
-                    SetComplete();
+                    return false;
                 }
             }
-            catch (Exception ex)
+
+            // 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 =>
             {
-                Debug.LogException(ex);
+                // 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);
+                }
             }
         }
     }

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

@@ -50,7 +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>
@@ -61,7 +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>
@@ -98,7 +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.
@@ -109,7 +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.
@@ -120,7 +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.
@@ -128,7 +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.
@@ -136,7 +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.
@@ -144,7 +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.
@@ -152,7 +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
@@ -282,231 +282,183 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void WriteValueBitPacked<T>(FastBufferWriter writer, T value) where T: unmanaged => writer.WriteValueSafe(value);
 #else
-
         /// <summary>
-        /// Maximum serializable value for a BitPacked ushort (minimum for unsigned is 0)
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const ushort BitPackedUshortMax = (1 << 15) - 1;
 
         /// <summary>
-        /// Maximum serializable value for a BitPacked short
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const short BitPackedShortMax = (1 << 14) - 1;
 
         /// <summary>
-        /// Minimum serializable value size for a BitPacked ushort
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const short BitPackedShortMin = -(1 << 14);
 
         /// <summary>
-        /// Maximum serializable value for a BitPacked uint (minimum for unsigned is 0)
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const uint BitPackedUintMax = (1 << 30) - 1;
 
         /// <summary>
-        /// Maximum serializable value for a BitPacked int
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const int BitPackedIntMax = (1 << 29) - 1;
 
         /// <summary>
-        /// Minimum serializable value size for a BitPacked int
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const int BitPackedIntMin = -(1 << 29);
 
         /// <summary>
-        /// Maximum serializable value for a BitPacked ulong (minimum for unsigned is 0)
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const ulong BitPackedULongMax = (1L << 61) - 1;
 
         /// <summary>
-        /// Maximum serializable value for a BitPacked long
+        /// Obsolete value that no longer carries meaning. Do not use.
         /// </summary>
         public const long BitPackedLongMax = (1L << 60) - 1;
 
         /// <summary>
-        /// Minimum serializable value size for a BitPacked long
+        /// 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.
-        /// The first bit indicates whether the value is 1 byte or 2.
-        /// The sign bit takes up another bit.
-        /// That leaves 14 bits for the value.
-        /// A value greater than 2^14-1 or less than -2^14 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 after zig-zag encoding.
+        /// Writes a 16-bit signed short 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 two bits indicate whether the value is 1, 2, or 3 bytes.
+        /// If the value uses 14 bits or less, the remaining 14 bits contain the value.
+        /// For performance, reasons, if the value is 15 bits or more, there will be six 0 bits, followed
+        /// 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.
-        /// The first bit indicates whether the value is 1 byte or 2.
-        /// That leaves 15 bits for the value.
-        /// A value greater than 2^15-1 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
-        /// most significant bit.
+        /// Writes a 16-bit unsigned short to the buffer in a bit-encoded packed format.
+        /// The first two bits indicate whether the value is 1, 2, or 3 bytes.
+        /// If the value uses 14 bits or less, the remaining 14 bits contain the value.
+        /// For performance, reasons, if the value is 15 bits or more, there will be six 0 bits, followed
+        /// 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, ushort value)
         {
-#if DEVELOPMENT_BUILD || UNITY_EDITOR
-            if (value >= BitPackedUshortMax)
+            if (value > (1 << 14) - 1)
             {
-                throw new ArgumentException("BitPacked ushorts must be <= 15 bits");
-            }
-#endif
-
-            if (value <= 0b0111_1111)
-            {
-                if (!writer.TryBeginWriteInternal(1))
+                if (!writer.TryBeginWriteInternal(3))
                 {
                     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.
-        /// The first three bits indicate whether the value is 1, 2, 3, 4, 5, 6, 7, or 8 bytes.
-        /// The sign bit takes up another bit.
-        /// That leaves 60 bits for the value.
-        /// A value greater than 2^60-1 or less than -2^60 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 four
-        /// most significant bits after zig-zag encoding.
+        /// Writes a 32-bit signed int 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 three bits indicate whether the value is 1, 2, 3, 4, or 5 bytes.
+        /// If the value uses 29 bits or less, the remaining 29 bits contain the value.
+        /// For performance, reasons, if the value is 30 bits or more, there will be five 0 bits, followed
+        /// 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.
-        /// The first three bits indicate whether the value is 1, 2, 3, 4, 5, 6, 7, or 8 bytes.
-        /// That leaves 31 bits for the value.
-        /// A value greater than 2^61-1 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 three
-        /// most significant bits.
+        /// 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, or 5 bytes.
+        /// If the value uses 29 bits or less, the remaining 29 bits contain the value.
+        /// For performance, reasons, if the value is 30 bits or more, there will be five 0 bits, followed
+        /// 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, ulong value)
+        public static void WriteValueBitPacked(FastBufferWriter writer, uint value)
         {
-#if DEVELOPMENT_BUILD || UNITY_EDITOR
-            if (value > BitPackedULongMax)
+            if (value > (1 << 29) - 1)
             {
-                throw new ArgumentException("BitPacked ulongs must be <= 61 bits");
+                if (!writer.TryBeginWriteInternal(5))
+                {
+                    throw new OverflowException("Writing past the end of the buffer");
+                }
+                writer.WriteByte(5);
+                writer.WriteValue(value);
+                return;
             }
-#endif
+
             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

@@ -11,7 +11,6 @@ namespace Unity.Netcode
     /// </summary>
     public static class ByteUnpacker
     {
-
 #if UNITY_NETCODE_DEBUG_NO_PACKING
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -58,7 +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);
         }
 
@@ -70,7 +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);
         }
 
@@ -109,11 +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)
-        {
-            ReadUInt32Packed(reader, out uint readValue);
-            value = (short)Arithmetic.ZigZagDecode(readValue);
-        }
+        public static void ReadValuePacked(FastBufferReader reader, out short value) => ReadValueBitPacked(reader, out value);
 
         /// <summary>
         /// Read an unsigned short (UInt16) as a varint from the stream.
@@ -121,11 +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)
-        {
-            ReadUInt32Packed(reader, out uint readValue);
-            value = (ushort)readValue;
-        }
+        public static void ReadValuePacked(FastBufferReader reader, out ushort value) => ReadValueBitPacked(reader, out value);
 
         /// <summary>
         /// Read a two-byte character as a varint from the stream.
@@ -135,7 +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;
         }
 
@@ -145,11 +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)
-        {
-            ReadUInt32Packed(reader, out uint readValue);
-            value = (int)Arithmetic.ZigZagDecode(readValue);
-        }
+        public static void ReadValuePacked(FastBufferReader reader, out int value) => ReadValueBitPacked(reader, out value);
 
         /// <summary>
         /// Read an unsigned int (UInt32) from the stream.
@@ -157,7 +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.
@@ -165,7 +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.
@@ -175,8 +162,7 @@ namespace Unity.Netcode
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void ReadValuePacked(FastBufferReader reader, out long value)
         {
-            ReadUInt64Packed(reader, out ulong readValue);
-            value = Arithmetic.ZigZagDecode(readValue);
+            ReadValueBitPacked(reader, out value);
         }
 
         /// <summary>
@@ -341,7 +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");
@@ -350,17 +338,23 @@ namespace Unity.Netcode
             switch (numBytes)
             {
                 case 1:
-                    *ptr = *data;
+                    ptr[0] = data[0];
                     break;
                 case 2:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
+                    ptr[0] = data[0];
+                    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>
@@ -386,7 +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");
@@ -395,26 +390,34 @@ namespace Unity.Netcode
             switch (numBytes)
             {
                 case 1:
-                    *ptr = *data;
+                    ptr[0] = data[0];
                     break;
                 case 2:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
                     break;
                 case 3:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
                     break;
                 case 4:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
-                    *(ptr + 3) = *(data + 3);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
+                    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>
@@ -440,7 +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");
@@ -449,109 +453,74 @@ namespace Unity.Netcode
             switch (numBytes)
             {
                 case 1:
-                    *ptr = *data;
+                    ptr[0] = data[0];
                     break;
                 case 2:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
                     break;
                 case 3:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
                     break;
                 case 4:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
-                    *(ptr + 3) = *(data + 3);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
+                    ptr[3] = data[3];
                     break;
                 case 5:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
-                    *(ptr + 3) = *(data + 3);
-                    *(ptr + 4) = *(data + 4);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
+                    ptr[3] = data[3];
+                    ptr[4] = data[4];
                     break;
                 case 6:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
-                    *(ptr + 3) = *(data + 3);
-                    *(ptr + 4) = *(data + 4);
-                    *(ptr + 5) = *(data + 5);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
+                    ptr[3] = data[3];
+                    ptr[4] = data[4];
+                    ptr[5] = data[5];
                     break;
                 case 7:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
-                    *(ptr + 3) = *(data + 3);
-                    *(ptr + 4) = *(data + 4);
-                    *(ptr + 5) = *(data + 5);
-                    *(ptr + 6) = *(data + 6);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
+                    ptr[3] = data[3];
+                    ptr[4] = data[4];
+                    ptr[5] = data[5];
+                    ptr[6] = data[6];
                     break;
                 case 8:
-                    *ptr = *data;
-                    *(ptr + 1) = *(data + 1);
-                    *(ptr + 2) = *(data + 2);
-                    *(ptr + 3) = *(data + 3);
-                    *(ptr + 4) = *(data + 4);
-                    *(ptr + 5) = *(data + 5);
-                    *(ptr + 6) = *(data + 6);
-                    *(ptr + 7) = *(data + 7);
+                    ptr[0] = data[0];
+                    ptr[1] = data[1];
+                    ptr[2] = data[2];
+                    ptr[3] = data[3];
+                    ptr[4] = data[4];
+                    ptr[5] = data[5];
+                    ptr[6] = data[6];
+                    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

@@ -65,7 +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;
             }
@@ -461,6 +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
@@ -1310,5 +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/NetworkObjectReference.cs

@@ -139,7 +139,16 @@ namespace Unity.Netcode
         /// </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) => Resolve(networkObjectRef).gameObject;
+        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"/>.

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 (targetNetworkObject != null)
+                            if (gameObject.TryGetComponent<NetworkObject>(out var targetNetworkObject))
                             {
                                 if (!m_PrefabInstanceToPrefabAsset.ContainsKey(targetNetworkObject.GlobalObjectIdHash))
                                 {

Runtime/Spawning/NetworkSpawnManager.cs

@@ -213,11 +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,
@@ -270,6 +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);
 
@@ -278,23 +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)
             {
-                NetworkManager.NetworkMetrics.TrackOwnershipChangeSent(client.Key, networkObject, size);
+                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)
                     {
@@ -309,53 +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 (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 scene management is disabled or the NetworkObject was dynamically spawned
+            if (!NetworkManager.NetworkConfig.EnableSceneManagement || !sceneObject.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;
-
-                    if (parentNetworkObject != null)
-                    {
-                        networkObject.transform.SetParent(parentNetworkObject.transform, true);
-                    }
-
-                    if (NetworkSceneManager.IsSpawnedObjectsPendingInDontDestroyOnLoad)
-                    {
-                        UnityEngine.Object.DontDestroyOnLoad(networkObject.gameObject);
-                    }
-
-                    return networkObject;
+                    isSpawnedByPrefabHandler = true;
                 }
                 else
                 {
@@ -383,31 +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)
+                    else
                     {
-                        networkObject.transform.SetParent(parentNetworkObject.transform, true);
+                        // Create prefab instance
+                        networkObject = UnityEngine.Object.Instantiate(networkPrefabReference).GetComponent<NetworkObject>();
+                        networkObject.NetworkManagerOwner = NetworkManager;
                     }
-
-                    if (NetworkSceneManager.IsSpawnedObjectsPendingInDontDestroyOnLoad)
-                    {
-                        UnityEngine.Object.DontDestroyOnLoad(networkObject.gameObject);
-                    }
-
-                    return networkObject;
                 }
             }
-            else
+            else // Get the in-scene placed NetworkObject
             {
-                var networkObject = NetworkManager.SceneManager.GetSceneRelativeInSceneNetworkObject(globalObjectIdHash, networkSceneHandle);
+                networkObject = NetworkManager.SceneManager.GetSceneRelativeInSceneNetworkObject(globalObjectIdHash, sceneObject.NetworkSceneHandle);
 
                 if (networkObject == null)
                 {
@@ -415,17 +393,89 @@ 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);
+                }
+            }
+
+            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);
+                    }
                 }
 
-                return networkObject;
+                // 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
@@ -454,8 +504,7 @@ namespace Unity.Netcode
         }
 
         // Ran on both server and client
-        internal void SpawnNetworkObjectLocally(NetworkObject networkObject, in NetworkObject.SceneObject sceneObject,
-            FastBufferReader variableData, bool destroyWithScene)
+        internal void SpawnNetworkObjectLocally(NetworkObject networkObject, in NetworkObject.SceneObject sceneObject, bool destroyWithScene)
         {
             if (networkObject == null)
             {
@@ -467,9 +516,7 @@ namespace Unity.Netcode
                 throw new SpawnStateException("Object is already spawned");
             }
 
-            networkObject.SetNetworkVariableData(variableData);
-
-            SpawnNetworkObjectLocallyCommon(networkObject, sceneObject.Header.NetworkObjectId, sceneObject.Header.IsSceneObject, sceneObject.Header.IsPlayerObject, sceneObject.Header.OwnerClientId, destroyWithScene);
+            SpawnNetworkObjectLocallyCommon(networkObject, sceneObject.NetworkObjectId, sceneObject.IsSceneObject, sceneObject.IsPlayerObject, sceneObject.OwnerClientId, destroyWithScene);
         }
 
         private void SpawnNetworkObjectLocallyCommon(NetworkObject networkObject, ulong networkId, bool sceneObject, bool playerObject, ulong ownerClientId, bool destroyWithScene)
@@ -545,7 +592,6 @@ namespace Unity.Netcode
                 }
             }
 
-            networkObject.SetCachedParent(networkObject.transform.parent);
             networkObject.ApplyNetworkParenting();
             NetworkObject.CheckOrphanChildren();
 
@@ -575,8 +621,6 @@ namespace Unity.Netcode
             };
             var size = NetworkManager.SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, clientId);
             NetworkManager.NetworkMetrics.TrackObjectSpawnSent(clientId, networkObject, size);
-
-            networkObject.MarkVariablesDirty(true);
         }
 
         internal ulong? GetSpawnParentId(NetworkObject networkObject)
@@ -614,7 +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;
@@ -645,7 +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++)
             {
@@ -675,7 +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++)
             {
@@ -702,7 +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++)
@@ -745,15 +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();
-                    if (isReparented && latestParent == networkObject.NetworkObjectId)
+                    var latestParent = spawnedNetObj.GetNetworkParenting();
+                    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/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;
 

Runtime/Timing/NetworkTimeSystem.cs

@@ -76,7 +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/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
-    /// <see cref="NetworkDriver.BeginSend"/>. This will fill the writer with as many messages as
-    /// possible. If the send is successful, call <see cref="Consume"/> to remove the data from the
-    /// queue.
+    /// messages, call <see cref="FillWriterWithMessages"/> or <see cref="FillWriterWithBytes"/>
+    /// with the <see cref="DataStreamWriter"/> obtained from <see cref="NetworkDriver.BeginSend"/>.
+    /// This will fill the writer with as many messages/bytes as possible. If the send is
+    /// 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.
-            if (m_Data.Length - TailIndex + HeadIndex >= sizeof(int) + message.Count)
+            // Move the data at the beginning of of m_Data. Either it will leave enough space for
+            // 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);
@@ -117,12 +150,38 @@ 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;
             }
 
-            return false;
+            // 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>
@@ -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/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);
-        static TransportFunctionPointer<NetworkPipelineStage.SendDelegate> SendFunction = new TransportFunctionPointer<NetworkPipelineStage.SendDelegate>(Send);
-        static TransportFunctionPointer<NetworkPipelineStage.InitializeConnectionDelegate> InitializeConnectionFunction = new TransportFunctionPointer<NetworkPipelineStage.InitializeConnectionDelegate>(InitializeConnection);
+        private static TransportFunctionPointer<NetworkPipelineStage.ReceiveDelegate> s_ReceiveFunction = new TransportFunctionPointer<NetworkPipelineStage.ReceiveDelegate>(Receive);
+        private static TransportFunctionPointer<NetworkPipelineStage.SendDelegate> s_SendFunction = new TransportFunctionPointer<NetworkPipelineStage.SendDelegate>(Send);
+        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,
-                SendFunction,
-                InitializeConnectionFunction,
+                s_ReceiveFunction,
+                s_SendFunction,
+                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

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: dc1e7a8dc597cf24c95e4acf92c0edf5
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Runtime/Transports/UTP/UnityTransport.cs

@@ -1,13 +1,29 @@
+// NetSim Implementation compilation boilerplate
+// All references to UNITY_MP_TOOLS_NETSIM_IMPLEMENTATION_ENABLED should be defined in the same way,
+// as any discrepancies are likely to result in build failures
+#if UNITY_EDITOR || (DEVELOPMENT_BUILD && !UNITY_MP_TOOLS_NETSIM_DISABLED_IN_DEVELOP) || (!DEVELOPMENT_BUILD && UNITY_MP_TOOLS_NETSIM_ENABLED_IN_RELEASE)
+#define UNITY_MP_TOOLS_NETSIM_IMPLEMENTATION_ENABLED
+#endif
+
 using System;
 using System.Collections.Generic;
 using UnityEngine;
 using NetcodeNetworkEvent = Unity.Netcode.NetworkEvent;
 using TransportNetworkEvent = Unity.Networking.Transport.NetworkEvent;
+using Unity.Burst;
 using Unity.Collections.LowLevel.Unsafe;
 using Unity.Collections;
+using Unity.Jobs;
 using Unity.Networking.Transport;
 using Unity.Networking.Transport.Relay;
 using Unity.Networking.Transport.Utilities;
+#if UTP_TRANSPORT_2_0_ABOVE
+using Unity.Networking.Transport.TLS;
+#endif
+
+#if !UTP_TRANSPORT_2_0_ABOVE
+using NetworkEndpoint = Unity.Networking.Transport.NetworkEndPoint;
+#endif
 
 namespace Unity.Netcode.Transports.UTP
 {
@@ -37,50 +53,48 @@ namespace Unity.Netcode.Transports.UTP
     /// </summary>
     public static class ErrorUtilities
     {
-        private const string k_NetworkSuccess = "Success";
-        private const string k_NetworkIdMismatch = "NetworkId is invalid, likely caused by stale connection {0}.";
-        private const string k_NetworkVersionMismatch = "NetworkVersion is invalid, likely caused by stale connection {0}.";
-        private const string k_NetworkStateMismatch = "Sending data while connecting on connection {0} is not allowed.";
-        private const string k_NetworkPacketOverflow = "Unable to allocate packet due to buffer overflow.";
-        private const string k_NetworkSendQueueFull = "Currently unable to queue packet as there is too many in-flight packets. This could be because the send queue size ('Max Send Queue Size') is too small.";
-        private const string k_NetworkHeaderInvalid = "Invalid Unity Transport Protocol header.";
-        private const string k_NetworkDriverParallelForErr = "The parallel network driver needs to process a single unique connection per job, processing a single connection multiple times in a parallel for is not supported.";
-        private const string k_NetworkSendHandleInvalid = "Invalid NetworkInterface Send Handle. Likely caused by pipeline send data corruption.";
-        private const string k_NetworkArgumentMismatch = "Invalid NetworkEndpoint Arguments.";
+        private static readonly FixedString128Bytes k_NetworkSuccess = "Success";
+        private static readonly FixedString128Bytes k_NetworkIdMismatch = "Invalid connection ID {0}.";
+        private static readonly FixedString128Bytes k_NetworkVersionMismatch = "Connection ID is invalid. Likely caused by sending on stale connection {0}.";
+        private static readonly FixedString128Bytes k_NetworkStateMismatch = "Connection state is invalid. Likely caused by sending on connection {0} which is stale or still connecting.";
+        private static readonly FixedString128Bytes k_NetworkPacketOverflow = "Packet is too large to be allocated by the transport.";
+        private static readonly FixedString128Bytes k_NetworkSendQueueFull = "Unable to queue packet in the transport. Likely caused by send queue size ('Max Send Queue Size') being too small.";
 
         /// <summary>
-        /// Convert error code to human readable error message.
+        /// Convert a UTP error code to human-readable error message.
         /// </summary>
-        /// <param name="error">Status code of the error</param>
-        /// <param name="connectionId">Subject connection ID of the error</param>
-        /// <returns>Human readable error message.</returns>
+        /// <param name="error">UTP error code.</param>
+        /// <param name="connectionId">ID of the connection on which the error occurred.</param>
+        /// <returns>Human-readable error message.</returns>
         public static string ErrorToString(Networking.Transport.Error.StatusCode error, ulong connectionId)
         {
-            switch (error)
+            return ErrorToString((int)error, connectionId);
+        }
+
+        internal static string ErrorToString(int error, ulong connectionId)
+        {
+            return ErrorToFixedString(error, connectionId).ToString();
+        }
+
+        internal static FixedString128Bytes ErrorToFixedString(int error, ulong connectionId)
+        {
+            switch ((Networking.Transport.Error.StatusCode)error)
             {
                 case Networking.Transport.Error.StatusCode.Success:
                     return k_NetworkSuccess;
                 case Networking.Transport.Error.StatusCode.NetworkIdMismatch:
-                    return string.Format(k_NetworkIdMismatch, connectionId);
+                    return FixedString.Format(k_NetworkIdMismatch, connectionId);
                 case Networking.Transport.Error.StatusCode.NetworkVersionMismatch:
-                    return string.Format(k_NetworkVersionMismatch, connectionId);
+                    return FixedString.Format(k_NetworkVersionMismatch, connectionId);
                 case Networking.Transport.Error.StatusCode.NetworkStateMismatch:
-                    return string.Format(k_NetworkStateMismatch, connectionId);
+                    return FixedString.Format(k_NetworkStateMismatch, connectionId);
                 case Networking.Transport.Error.StatusCode.NetworkPacketOverflow:
                     return k_NetworkPacketOverflow;
                 case Networking.Transport.Error.StatusCode.NetworkSendQueueFull:
                     return k_NetworkSendQueueFull;
-                case Networking.Transport.Error.StatusCode.NetworkHeaderInvalid:
-                    return k_NetworkHeaderInvalid;
-                case Networking.Transport.Error.StatusCode.NetworkDriverParallelForErr:
-                    return k_NetworkDriverParallelForErr;
-                case Networking.Transport.Error.StatusCode.NetworkSendHandleInvalid:
-                    return k_NetworkSendHandleInvalid;
-                case Networking.Transport.Error.StatusCode.NetworkArgumentMismatch:
-                    return k_NetworkArgumentMismatch;
+                default:
+                    return FixedString.Format("Unknown error code {0}.", error);
             }
-
-            return $"Unknown ErrorCode {Enum.GetName(typeof(Networking.Transport.Error.StatusCode), error)}";
         }
     }
 
@@ -88,6 +102,7 @@ namespace Unity.Netcode.Transports.UTP
     /// The Netcode for GameObjects NetworkTransport for UnityTransport.
     /// Note: This is highly recommended to use over UNet.
     /// </summary>
+    [AddComponentMenu("Netcode/Unity Transport")]
     public partial class UnityTransport : NetworkTransport, INetworkStreamDriverConstructor
     {
         /// <summary>
@@ -125,8 +140,13 @@ namespace Unity.Netcode.Transports.UTP
         /// <summary>
         /// The default maximum send queue size
         /// </summary>
+        [Obsolete("MaxSendQueueSize is now determined dynamically (can still be set programmatically using the MaxSendQueueSize property). This initial value is not used anymore.", false)]
         public const int InitialMaxSendQueueSize = 16 * InitialMaxPayloadSize;
 
+        // Maximum reliable throughput, assuming the full reliable window can be sent on every
+        // frame at 60 FPS. This will be a large over-estimation in any realistic scenario.
+        private const int k_MaxReliableThroughput = (NetworkParameterConstants.MTU * 32 * 60) / 1000; // bytes per millisecond
+
         private static ConnectionAddressData s_DefaultConnectionAddressData = new ConnectionAddressData { Address = "127.0.0.1", Port = 7777, ServerListenAddress = string.Empty };
 
 #pragma warning disable IDE1006 // Naming Styles
@@ -146,6 +166,30 @@ namespace Unity.Netcode.Transports.UTP
         [SerializeField]
         private ProtocolType m_ProtocolType;
 
+#if UTP_TRANSPORT_2_0_ABOVE
+        [Tooltip("Per default the client/server will communicate over UDP. Set to true to communicate with WebSocket.")]
+        [SerializeField]
+        private bool m_UseWebSockets = false;
+
+        public bool UseWebSockets
+        {
+            get => m_UseWebSockets;
+            set => m_UseWebSockets = value;
+        }
+
+        /// <summary>
+        /// Per default the client/server communication will not be encrypted. Select true to enable DTLS for UDP and TLS for Websocket.
+        /// </summary>
+        [Tooltip("Per default the client/server communication will not be encrypted. Select true to enable DTLS for UDP and TLS for Websocket.")]
+        [SerializeField]
+        private bool m_UseEncryption = false;
+        public bool UseEncryption
+        {
+            get => m_UseEncryption;
+            set => m_UseEncryption = value;
+        }
+#endif
+
         [Tooltip("The maximum amount of packets that can be in the internal send/receive queues. Basically this is how many packets can be sent/received in a single update/frame.")]
         [SerializeField]
         private int m_MaxPacketQueueSize = InitialMaxPacketQueueSize;
@@ -169,15 +213,17 @@ namespace Unity.Netcode.Transports.UTP
             set => m_MaxPayloadSize = value;
         }
 
-        [Tooltip("The maximum size in bytes of the transport send queue. The send queue accumulates messages for batching and stores messages when other internal send queues are full. If you routinely observe an error about too many in-flight packets, try increasing this.")]
-        [SerializeField]
-        private int m_MaxSendQueueSize = InitialMaxSendQueueSize;
+        private int m_MaxSendQueueSize = 0;
 
         /// <summary>The maximum size in bytes of the transport send queue.</summary>
         /// <remarks>
         /// The send queue accumulates messages for batching and stores messages when other internal
-        /// send queues are full. If you routinely observe an error about too many in-flight packets,
-        /// try increasing this.
+        /// send queues are full. Note that there should not be any need to set this value manually
+        /// since the send queue size is dynamically sized based on need.
+        ///
+        /// This value should only be set if you have particular requirements (e.g. if you want to
+        /// limit the memory usage of the send queues). Note however that setting this value too low
+        /// can easily lead to disconnections under heavy traffic.
         /// </remarks>
         public int MaxSendQueueSize
         {
@@ -263,12 +309,14 @@ namespace Unity.Netcode.Transports.UTP
             [SerializeField]
             public string ServerListenAddress;
 
-            private static NetworkEndPoint ParseNetworkEndpoint(string ip, ushort port)
+            private static NetworkEndpoint ParseNetworkEndpoint(string ip, ushort port)
             {
-                if (!NetworkEndPoint.TryParse(ip, port, out var endpoint))
+                NetworkEndpoint endpoint = default;
+
+                if (!NetworkEndpoint.TryParse(ip, port, out endpoint, NetworkFamily.Ipv4) &&
+                    !NetworkEndpoint.TryParse(ip, port, out endpoint, NetworkFamily.Ipv6))
                 {
                     Debug.LogError($"Invalid network endpoint: {ip}:{port}.");
-                    return default;
                 }
 
                 return endpoint;
@@ -277,12 +325,12 @@ namespace Unity.Netcode.Transports.UTP
             /// <summary>
             /// Endpoint (IP address and port) clients will connect to.
             /// </summary>
-            public NetworkEndPoint ServerEndPoint => ParseNetworkEndpoint(Address, Port);
+            public NetworkEndpoint ServerEndPoint => ParseNetworkEndpoint(Address, Port);
 
             /// <summary>
             /// Endpoint (IP address and port) server will listen/bind on.
             /// </summary>
-            public NetworkEndPoint ListenEndPoint => ParseNetworkEndpoint((ServerListenAddress == string.Empty) ? Address : ServerListenAddress, Port);
+            public NetworkEndpoint ListenEndPoint => ParseNetworkEndpoint((ServerListenAddress?.Length == 0) ? Address : ServerListenAddress, Port);
         }
 
         /// <summary>
@@ -326,6 +374,9 @@ namespace Unity.Netcode.Transports.UTP
         /// - packet jitter (variances in latency, see: https://en.wikipedia.org/wiki/Jitter)
         /// - packet drop rate (packet loss)
         /// </summary>
+#if UTP_TRANSPORT_2_0_ABOVE
+        [Obsolete("DebugSimulator is no longer supported and has no effect. Use Network Simulator from the Multiplayer Tools package.", false)]
+#endif
         public SimulatorParameters DebugSimulator = new SimulatorParameters
         {
             PacketDelayMS = 0,
@@ -333,6 +384,8 @@ namespace Unity.Netcode.Transports.UTP
             PacketDropRate = 0
         };
 
+        internal uint? DebugSimulatorRandomSeed { get; set; } = null;
+
         private struct PacketLossCache
         {
             public int PacketsReceived;
@@ -340,6 +393,10 @@ namespace Unity.Netcode.Transports.UTP
             public float PacketLoss;
         };
 
+        internal static event Action<int, NetworkDriver> TransportInitialized;
+        internal static event Action<int> TransportDisposed;
+        internal NetworkDriver NetworkDriver => m_Driver;
+
         private PacketLossCache m_PacketLossCache = new PacketLossCache();
 
         private State m_State = State.Disconnected;
@@ -383,6 +440,8 @@ namespace Unity.Netcode.Transports.UTP
                 out m_UnreliableFragmentedPipeline,
                 out m_UnreliableSequencedFragmentedPipeline,
                 out m_ReliableSequencedPipeline);
+
+            TransportInitialized?.Invoke(GetInstanceID(), NetworkDriver);
         }
 
         private void DisposeInternals()
@@ -400,6 +459,8 @@ namespace Unity.Netcode.Transports.UTP
             }
 
             m_SendQueue.Clear();
+
+            TransportDisposed?.Invoke(GetInstanceID());
         }
 
         private NetworkPipeline SelectSendPipeline(NetworkDelivery delivery)
@@ -425,7 +486,7 @@ namespace Unity.Netcode.Transports.UTP
 
         private bool ClientBindAndConnect()
         {
-            var serverEndpoint = default(NetworkEndPoint);
+            var serverEndpoint = default(NetworkEndpoint);
 
             if (m_ProtocolType == ProtocolType.RelayUnityTransport)
             {
@@ -438,6 +499,7 @@ namespace Unity.Netcode.Transports.UTP
                 }
 
                 m_NetworkSettings.WithRelayParameters(ref m_RelayServerData, m_HeartbeatTimeoutMS);
+                serverEndpoint = m_RelayServerData.Endpoint;
             }
             else
             {
@@ -446,7 +508,8 @@ namespace Unity.Netcode.Transports.UTP
 
             InitDriver();
 
-            int result = m_Driver.Bind(NetworkEndPoint.AnyIpv4);
+            var bindEndpoint = serverEndpoint.Family == NetworkFamily.Ipv6 ? NetworkEndpoint.AnyIpv6 : NetworkEndpoint.AnyIpv4;
+            int result = m_Driver.Bind(bindEndpoint);
             if (result != 0)
             {
                 Debug.LogError("Client failed to bind");
@@ -459,7 +522,7 @@ namespace Unity.Netcode.Transports.UTP
             return true;
         }
 
-        private bool ServerBindAndListen(NetworkEndPoint endPoint)
+        private bool ServerBindAndListen(NetworkEndpoint endPoint)
         {
             InitDriver();
 
@@ -481,51 +544,13 @@ namespace Unity.Netcode.Transports.UTP
             return true;
         }
 
-        private static RelayAllocationId ConvertFromAllocationIdBytes(byte[] allocationIdBytes)
-        {
-            unsafe
-            {
-                fixed (byte* ptr = allocationIdBytes)
-                {
-                    return RelayAllocationId.FromBytePointer(ptr, allocationIdBytes.Length);
-                }
-            }
-        }
-
-        private static RelayHMACKey ConvertFromHMAC(byte[] hmac)
-        {
-            unsafe
-            {
-                fixed (byte* ptr = hmac)
-                {
-                    return RelayHMACKey.FromBytePointer(ptr, RelayHMACKey.k_Length);
-                }
-            }
-        }
-
-        private static RelayConnectionData ConvertConnectionData(byte[] connectionData)
-        {
-            unsafe
-            {
-                fixed (byte* ptr = connectionData)
-                {
-                    return RelayConnectionData.FromBytePointer(ptr, RelayConnectionData.k_Length);
-                }
-            }
-        }
-
-        internal void SetMaxPayloadSize(int maxPayloadSize)
-        {
-            m_MaxPayloadSize = maxPayloadSize;
-        }
-
         private void SetProtocol(ProtocolType inProtocol)
         {
             m_ProtocolType = inProtocol;
         }
 
         /// <summary>Set the relay server data for the server.</summary>
-        /// <param name="ipv4Address">IP address of the relay server.</param>
+        /// <param name="ipv4Address">IP address or hostname of the relay server.</param>
         /// <param name="port">UDP port of the relay server.</param>
         /// <param name="allocationIdBytes">Allocation ID as a byte array.</param>
         /// <param name="keyBytes">Allocation key as a byte array.</param>
@@ -534,39 +559,21 @@ namespace Unity.Netcode.Transports.UTP
         /// <param name="isSecure">Whether the connection is secure (uses DTLS).</param>
         public void SetRelayServerData(string ipv4Address, ushort port, byte[] allocationIdBytes, byte[] keyBytes, byte[] connectionDataBytes, byte[] hostConnectionDataBytes = null, bool isSecure = false)
         {
-            RelayConnectionData hostConnectionData;
-
-            if (!NetworkEndPoint.TryParse(ipv4Address, port, out var serverEndpoint))
-            {
-                Debug.LogError($"Invalid address {ipv4Address}:{port}");
-
-                // We set this to default to cause other checks to fail to state you need to call this
-                // function again.
-                m_RelayServerData = default;
-                return;
-            }
-
-            var allocationId = ConvertFromAllocationIdBytes(allocationIdBytes);
-            var key = ConvertFromHMAC(keyBytes);
-            var connectionData = ConvertConnectionData(connectionDataBytes);
-
-            if (hostConnectionDataBytes != null)
-            {
-                hostConnectionData = ConvertConnectionData(hostConnectionDataBytes);
-            }
-            else
-            {
-                hostConnectionData = connectionData;
-            }
-
-            m_RelayServerData = new RelayServerData(ref serverEndpoint, 0, ref allocationId, ref connectionData, ref hostConnectionData, ref key, isSecure);
-            m_RelayServerData.ComputeNewNonce();
+            var hostConnectionData = hostConnectionDataBytes ?? connectionDataBytes;
+            m_RelayServerData = new RelayServerData(ipv4Address, port, allocationIdBytes, connectionDataBytes, hostConnectionData, keyBytes, isSecure);
+            SetProtocol(ProtocolType.RelayUnityTransport);
+        }
 
+        /// <summary>Set the relay server data (using the lower-level Unity Transport data structure).</summary>
+        /// <param name="serverData">Data for the Relay server to use.</param>
+        public void SetRelayServerData(RelayServerData serverData)
+        {
+            m_RelayServerData = serverData;
             SetProtocol(ProtocolType.RelayUnityTransport);
         }
 
         /// <summary>Set the relay server data for the host.</summary>
-        /// <param name="ipAddress">IP address of the relay server.</param>
+        /// <param name="ipAddress">IP address or hostname of the relay server.</param>
         /// <param name="port">UDP port of the relay server.</param>
         /// <param name="allocationId">Allocation ID as a byte array.</param>
         /// <param name="key">Allocation key as a byte array.</param>
@@ -578,7 +585,7 @@ namespace Unity.Netcode.Transports.UTP
         }
 
         /// <summary>Set the relay server data for the host.</summary>
-        /// <param name="ipAddress">IP address of the relay server.</param>
+        /// <param name="ipAddress">IP address or hostname of the relay server.</param>
         /// <param name="port">UDP port of the relay server.</param>
         /// <param name="allocationId">Allocation ID as a byte array.</param>
         /// <param name="key">Allocation key as a byte array.</param>
@@ -593,7 +600,7 @@ namespace Unity.Netcode.Transports.UTP
         /// <summary>
         /// Sets IP and Port information. This will be ignored if using the Unity Relay and you should call <see cref="SetRelayServerData"/>
         /// </summary>
-        /// <param name="ipv4Address">The remote IP address</param>
+        /// <param name="ipv4Address">The remote IP address (despite the name, can be an IPv6 address)</param>
         /// <param name="port">The remote port</param>
         /// <param name="listenAddress">The local listen address</param>
         public void SetConnectionData(string ipv4Address, ushort port, string listenAddress = null)
@@ -613,7 +620,7 @@ namespace Unity.Netcode.Transports.UTP
         /// </summary>
         /// <param name="endPoint">The remote end point</param>
         /// <param name="listenEndPoint">The local listen endpoint</param>
-        public void SetConnectionData(NetworkEndPoint endPoint, NetworkEndPoint listenEndPoint = default)
+        public void SetConnectionData(NetworkEndpoint endPoint, NetworkEndpoint listenEndPoint = default)
         {
             string serverAddress = endPoint.Address.Split(':')[0];
 
@@ -634,6 +641,9 @@ namespace Unity.Netcode.Transports.UTP
         /// <param name="packetDelay">Packet delay in milliseconds.</param>
         /// <param name="packetJitter">Packet jitter in milliseconds.</param>
         /// <param name="dropRate">Packet drop percentage.</param>
+#if UTP_TRANSPORT_2_0_ABOVE
+        [Obsolete("SetDebugSimulatorParameters is no longer supported and has no effect. Use Network Simulator from the Multiplayer Tools package.", false)]
+#endif
         public void SetDebugSimulatorParameters(int packetDelay, int packetJitter, int dropRate)
         {
             if (m_Driver.IsCreated)
@@ -662,57 +672,76 @@ namespace Unity.Netcode.Transports.UTP
             else
             {
                 m_NetworkSettings.WithRelayParameters(ref m_RelayServerData, m_HeartbeatTimeoutMS);
-                return ServerBindAndListen(NetworkEndPoint.AnyIpv4);
+                return ServerBindAndListen(NetworkEndpoint.AnyIpv4);
+            }
+        }
+
+        [BurstCompile]
+        private struct SendBatchedMessagesJob : IJob
+        {
+            public NetworkDriver.Concurrent Driver;
+            public SendTarget Target;
+            public BatchedSendQueue Queue;
+            public NetworkPipeline ReliablePipeline;
+
+            public void Execute()
+            {
+                var clientId = Target.ClientId;
+                var connection = ParseClientId(clientId);
+                var pipeline = Target.NetworkPipeline;
+
+                while (!Queue.IsEmpty)
+                {
+                    var result = Driver.BeginSend(pipeline, connection, out var writer);
+                    if (result != (int)Networking.Transport.Error.StatusCode.Success)
+                    {
+                        Debug.LogError($"Error sending message: {ErrorUtilities.ErrorToFixedString(result, clientId)}");
+                        return;
+                    }
+
+                    // We don't attempt to send entire payloads over the reliable pipeline. Instead we
+                    // fragment it manually. This is safe and easy to do since the reliable pipeline
+                    // basically implements a stream, so as long as we separate the different messages
+                    // in the stream (the send queue does that automatically) we are sure they'll be
+                    // reassembled properly at the other end. This allows us to lift the limit of ~44KB
+                    // on reliable payloads (because of the reliable window size).
+                    var written = pipeline == ReliablePipeline ? Queue.FillWriterWithBytes(ref writer) : Queue.FillWriterWithMessages(ref writer);
+
+                    result = Driver.EndSend(writer);
+                    if (result == written)
+                    {
+                        // Batched message was sent successfully. Remove it from the queue.
+                        Queue.Consume(written);
+                    }
+                    else
+                    {
+                        // Some error occured. If it's just the UTP queue being full, then don't log
+                        // anything since that's okay (the unsent message(s) are still in the queue
+                        // and we'll retry sending them later). Otherwise log the error and remove the
+                        // message from the queue (we don't want to resend it again since we'll likely
+                        // just get the same error again).
+                        if (result != (int)Networking.Transport.Error.StatusCode.NetworkSendQueueFull)
+                        {
+                            Debug.LogError($"Error sending the message: {ErrorUtilities.ErrorToFixedString(result, clientId)}");
+                            Queue.Consume(written);
+                        }
+
+                        return;
+                    }
+                }
             }
         }
 
         // Send as many batched messages from the queue as possible.
         private void SendBatchedMessages(SendTarget sendTarget, BatchedSendQueue queue)
         {
-            var clientId = sendTarget.ClientId;
-            var connection = ParseClientId(clientId);
-            var pipeline = sendTarget.NetworkPipeline;
-
-            while (!queue.IsEmpty)
+            new SendBatchedMessagesJob
             {
-                var result = m_Driver.BeginSend(pipeline, connection, out var writer);
-                if (result != (int)Networking.Transport.Error.StatusCode.Success)
-                {
-                    Debug.LogError("Error sending the message: " +
-                        ErrorUtilities.ErrorToString((Networking.Transport.Error.StatusCode)result, clientId));
-                    return;
-                }
-
-                // We don't attempt to send entire payloads over the reliable pipeline. Instead we
-                // fragment it manually. This is safe and easy to do since the reliable pipeline
-                // basically implements a stream, so as long as we separate the different messages
-                // in the stream (the send queue does that automatically) we are sure they'll be
-                // reassembled properly at the other end. This allows us to lift the limit of ~44KB
-                // on reliable payloads (because of the reliable window size).
-                var written = pipeline == m_ReliableSequencedPipeline ? queue.FillWriterWithBytes(ref writer) : queue.FillWriterWithMessages(ref writer);
-
-                result = m_Driver.EndSend(writer);
-                if (result == written)
-                {
-                    // Batched message was sent successfully. Remove it from the queue.
-                    queue.Consume(written);
-                }
-                else
-                {
-                    // Some error occured. If it's just the UTP queue being full, then don't log
-                    // anything since that's okay (the unsent message(s) are still in the queue
-                    // and we'll retry sending the later). Otherwise log the error and remove the
-                    // message from the queue (we don't want to resend it again since we'll likely
-                    // just get the same error again).
-                    if (result != (int)Networking.Transport.Error.StatusCode.NetworkSendQueueFull)
-                    {
-                        Debug.LogError("Error sending the message: " + ErrorUtilities.ErrorToString((Networking.Transport.Error.StatusCode)result, clientId));
-                        queue.Consume(written);
-                    }
-
-                    return;
-                }
-            }
+                Driver = m_Driver.ToConcurrent(),
+                Target = sendTarget,
+                Queue = queue,
+                ReliablePipeline = m_ReliableSequencedPipeline
+            }.Run();
         }
 
         private bool AcceptConnection()
@@ -891,7 +920,7 @@ namespace Unity.Netcode.Transports.UTP
 
         private void ExtractNetworkMetricsForClient(ulong transportClientId)
         {
-            var networkConnection =  ParseClientId(transportClientId);
+            var networkConnection = ParseClientId(transportClientId);
             ExtractNetworkMetricsFromPipeline(m_UnreliableFragmentedPipeline, networkConnection);
             ExtractNetworkMetricsFromPipeline(m_UnreliableSequencedFragmentedPipeline, networkConnection);
             ExtractNetworkMetricsFromPipeline(m_ReliableSequencedPipeline, networkConnection);
@@ -907,7 +936,11 @@ namespace Unity.Netcode.Transports.UTP
         {
             //Don't need to dispose of the buffers, they are filled with data pointers.
             m_Driver.GetPipelineBuffers(pipeline,
+#if UTP_TRANSPORT_2_0_ABOVE
+                NetworkPipelineStageId.Get<NetworkMetricsPipelineStage>(),
+#else
                 NetworkPipelineStageCollection.GetStageId(typeof(NetworkMetricsPipelineStage)),
+#endif
                 networkConnection,
                 out _,
                 out _,
@@ -934,7 +967,11 @@ namespace Unity.Netcode.Transports.UTP
             }
 
             m_Driver.GetPipelineBuffers(m_ReliableSequencedPipeline,
+#if UTP_TRANSPORT_2_0_ABOVE
+                NetworkPipelineStageId.Get<ReliableSequencedPipelineStage>(),
+#else
                 NetworkPipelineStageCollection.GetStageId(typeof(ReliableSequencedPipelineStage)),
+#endif
                 networkConnection,
                 out _,
                 out _,
@@ -956,7 +993,11 @@ namespace Unity.Netcode.Transports.UTP
             }
 
             m_Driver.GetPipelineBuffers(m_ReliableSequencedPipeline,
+#if UTP_TRANSPORT_2_0_ABOVE
+                NetworkPipelineStageId.Get<ReliableSequencedPipelineStage>(),
+#else
                 NetworkPipelineStageCollection.GetStageId(typeof(ReliableSequencedPipelineStage)),
+#endif
                 networkConnection,
                 out _,
                 out _,
@@ -1117,11 +1158,12 @@ namespace Unity.Netcode.Transports.UTP
             // account for the overhead of its length when we store it in the send queue.
             var fragmentationCapacity = m_MaxPayloadSize + BatchedSendQueue.PerMessageOverhead;
 
-            m_NetworkSettings
-                .WithFragmentationStageParameters(payloadCapacity: fragmentationCapacity)
-                .WithBaselibNetworkInterfaceParameters(
-                    receiveQueueCapacity: m_MaxPacketQueueSize,
-                    sendQueueCapacity: m_MaxPacketQueueSize);
+            m_NetworkSettings.WithFragmentationStageParameters(payloadCapacity: fragmentationCapacity);
+#if !UTP_TRANSPORT_2_0_ABOVE
+            m_NetworkSettings.WithBaselibNetworkInterfaceParameters(
+                receiveQueueCapacity: m_MaxPacketQueueSize,
+                sendQueueCapacity: m_MaxPacketQueueSize);
+#endif
 #endif
         }
 
@@ -1159,7 +1201,23 @@ namespace Unity.Netcode.Transports.UTP
             var sendTarget = new SendTarget(clientId, pipeline);
             if (!m_SendQueue.TryGetValue(sendTarget, out var queue))
             {
-                queue = new BatchedSendQueue(Math.Max(m_MaxSendQueueSize, m_MaxPayloadSize));
+                // The maximum size of a send queue is determined according to the disconnection
+                // timeout. The idea being that if the send queue contains enough reliable data that
+                // sending it all out would take longer than the disconnection timeout, then there's
+                // no point storing even more in the queue (it would be like having a ping higher
+                // than the disconnection timeout, which is far into the realm of unplayability).
+                //
+                // The throughput used to determine what consists the maximum send queue size is
+                // the maximum theoritical throughput of the reliable pipeline assuming we only send
+                // on each update at 60 FPS, which turns out to be around 2.688 MB/s.
+                //
+                // Note that we only care about reliable throughput for send queues because that's
+                // the only case where a full send queue causes a connection loss. Full unreliable
+                // send queues are dealt with by flushing it out to the network or simply dropping
+                // new messages if that fails.
+                var maxCapacity = m_MaxSendQueueSize > 0 ? m_MaxSendQueueSize : m_DisconnectTimeoutMS * k_MaxReliableThroughput;
+
+                queue = new BatchedSendQueue(Math.Max(maxCapacity, m_MaxPayloadSize));
                 m_SendQueue.Add(sendTarget, queue);
             }
 
@@ -1173,8 +1231,7 @@ namespace Unity.Netcode.Transports.UTP
 
                     var ngoClientId = NetworkManager?.TransportIdToClientId(clientId) ?? clientId;
                     Debug.LogError($"Couldn't add payload of size {payload.Count} to reliable send queue. " +
-                        $"Closing connection {ngoClientId} as reliability guarantees can't be maintained. " +
-                        $"Perhaps 'Max Send Queue Size' ({m_MaxSendQueueSize}) is too small for workload.");
+                        $"Closing connection {ngoClientId} as reliability guarantees can't be maintained.");
 
                     if (clientId == m_ServerClientId)
                     {
@@ -1223,9 +1280,9 @@ namespace Unity.Netcode.Transports.UTP
             }
 
             var succeeded = ClientBindAndConnect();
-            if (!succeeded)
+            if (!succeeded && m_Driver.IsCreated)
             {
-                Shutdown();
+                m_Driver.Dispose();
             }
             return succeeded;
         }
@@ -1250,16 +1307,16 @@ namespace Unity.Netcode.Transports.UTP
             {
                 case ProtocolType.UnityTransport:
                     succeeded = ServerBindAndListen(ConnectionData.ListenEndPoint);
-                    if (!succeeded)
+                    if (!succeeded && m_Driver.IsCreated)
                     {
-                        Shutdown();
+                        m_Driver.Dispose();
                     }
                     return succeeded;
                 case ProtocolType.RelayUnityTransport:
                     succeeded = StartRelayServer();
-                    if (!succeeded)
+                    if (!succeeded && m_Driver.IsCreated)
                     {
-                        Shutdown();
+                        m_Driver.Dispose();
                     }
                     return succeeded;
                 default:
@@ -1298,16 +1355,65 @@ namespace Unity.Netcode.Transports.UTP
             m_ServerClientId = 0;
         }
 
-        private void ConfigureSimulator()
+#if UTP_TRANSPORT_2_0_ABOVE
+        private void ConfigureSimulatorForUtp2()
+        {
+            // As DebugSimulator is deprecated, the 'packetDelayMs', 'packetJitterMs' and 'packetDropPercentage'
+            // parameters are set to the default and are supposed to be changed using Network Simulator tool instead.
+            m_NetworkSettings.WithSimulatorStageParameters(
+                maxPacketCount: 300, // TODO Is there any way to compute a better value?
+                maxPacketSize: NetworkParameterConstants.MTU,
+                packetDelayMs: 0,
+                packetJitterMs: 0,
+                packetDropPercentage: 0,
+                randomSeed: DebugSimulatorRandomSeed ?? (uint)System.Diagnostics.Stopwatch.GetTimestamp()
+                , mode: ApplyMode.AllPackets
+            );
+
+            m_NetworkSettings.WithNetworkSimulatorParameters();
+        }
+#else
+        private void ConfigureSimulatorForUtp1()
         {
             m_NetworkSettings.WithSimulatorStageParameters(
                 maxPacketCount: 300, // TODO Is there any way to compute a better value?
                 maxPacketSize: NetworkParameterConstants.MTU,
                 packetDelayMs: DebugSimulator.PacketDelayMS,
                 packetJitterMs: DebugSimulator.PacketJitterMS,
-                packetDropPercentage: DebugSimulator.PacketDropRate
+                packetDropPercentage: DebugSimulator.PacketDropRate,
+                randomSeed: DebugSimulatorRandomSeed ?? (uint)System.Diagnostics.Stopwatch.GetTimestamp()
             );
         }
+#endif
+
+        private string m_ServerPrivateKey;
+        private string m_ServerCertificate;
+
+        private string m_ServerCommonName;
+        private string m_ClientCaCertificate;
+
+        /// <summary>Set the server parameters for encryption.</summary>
+        /// <param name="serverCertificate">Public certificate for the server (PEM format).</param>
+        /// <param name="serverPrivateKey">Private key for the server (PEM format).</param>
+        public void SetServerSecrets(string serverCertificate, string serverPrivateKey)
+        {
+            m_ServerPrivateKey = serverPrivateKey;
+            m_ServerCertificate = serverCertificate;
+        }
+
+        /// <summary>Set the client parameters for encryption.</summary>
+        /// <remarks>
+        /// If the CA certificate is not provided, validation will be done against the OS/browser
+        /// certificate store. This is what you'd want if using certificates from a known provider.
+        /// For self-signed certificates, the CA certificate needs to be provided.
+        /// </remarks>
+        /// <param name="serverCommonName">Common name of the server (typically hostname).</param>
+        /// <param name="caCertificate">CA certificate used to validate the server's authenticity.</param>
+        public void SetClientSecrets(string serverCommonName, string caCertificate = null)
+        {
+            m_ServerCommonName = serverCommonName;
+            m_ClientCaCertificate = caCertificate;
+        }
 
         /// <summary>
         /// Creates the internal NetworkDriver
@@ -1322,22 +1428,118 @@ namespace Unity.Netcode.Transports.UTP
             out NetworkPipeline unreliableSequencedFragmentedPipeline,
             out NetworkPipeline reliableSequencedPipeline)
         {
-#if MULTIPLAYER_TOOLS_1_0_0_PRE_7
+#if MULTIPLAYER_TOOLS_1_0_0_PRE_7 && !UTP_TRANSPORT_2_0_ABOVE
             NetworkPipelineStageCollection.RegisterPipelineStage(new NetworkMetricsPipelineStage());
 #endif
 
-#if UNITY_EDITOR || DEVELOPMENT_BUILD
-            ConfigureSimulator();
+#if UTP_TRANSPORT_2_0_ABOVE && UNITY_MP_TOOLS_NETSIM_IMPLEMENTATION_ENABLED
+            ConfigureSimulatorForUtp2();
+#elif !UTP_TRANSPORT_2_0_ABOVE && (UNITY_EDITOR || DEVELOPMENT_BUILD)
+            ConfigureSimulatorForUtp1();
 #endif
 
             m_NetworkSettings.WithNetworkConfigParameters(
                 maxConnectAttempts: transport.m_MaxConnectAttempts,
                 connectTimeoutMS: transport.m_ConnectTimeoutMS,
                 disconnectTimeoutMS: transport.m_DisconnectTimeoutMS,
+#if UTP_TRANSPORT_2_0_ABOVE
+                sendQueueCapacity: m_MaxPacketQueueSize,
+                receiveQueueCapacity: m_MaxPacketQueueSize,
+#endif
                 heartbeatTimeoutMS: transport.m_HeartbeatTimeoutMS);
 
-            driver = NetworkDriver.Create(m_NetworkSettings);
+#if UNITY_WEBGL && !UNITY_EDITOR
+            if (NetworkManager.IsServer)
+            {
+                throw new Exception("WebGL as a server is not supported by Unity Transport, outside the Editor.");
+            }
+#endif
 
+#if UTP_TRANSPORT_2_0_ABOVE
+            if (m_UseEncryption)
+            {
+                if (m_ProtocolType == ProtocolType.RelayUnityTransport)
+                {
+                    if (m_RelayServerData.IsSecure == 0)
+                    {
+                        // log an error because we have mismatched configuration
+                        Debug.LogError("Mismatched security configuration, between Relay and local NetworkManager settings");
+                    }
+
+                    // No need to to anything else if using Relay because UTP will handle the
+                    // configuration of the security parameters on its own.
+                }
+                else
+                {
+                    if (NetworkManager.IsServer)
+                    {
+                        if (String.IsNullOrEmpty(m_ServerCertificate) || String.IsNullOrEmpty(m_ServerPrivateKey))
+                        {
+                            throw new Exception("In order to use encrypted communications, when hosting, you must set the server certificate and key.");
+                        }
+
+                        m_NetworkSettings.WithSecureServerParameters(m_ServerCertificate, m_ServerPrivateKey);
+                    }
+                    else
+                    {
+                        if (String.IsNullOrEmpty(m_ServerCommonName))
+                        {
+                            throw new Exception("In order to use encrypted communications, clients must set the server common name.");
+                        }
+                        else if (String.IsNullOrEmpty(m_ClientCaCertificate))
+                        {
+                            m_NetworkSettings.WithSecureClientParameters(m_ServerCommonName);
+                        }
+                        else
+                        {
+                            m_NetworkSettings.WithSecureClientParameters(m_ClientCaCertificate, m_ServerCommonName);
+                        }
+                    }
+                }
+            }
+#endif
+
+#if UTP_TRANSPORT_2_0_ABOVE
+            if (m_UseWebSockets)
+            {
+                driver = NetworkDriver.Create(new WebSocketNetworkInterface(), m_NetworkSettings);
+            }
+            else
+            {
+#if UNITY_WEBGL
+                Debug.LogWarning($"WebSockets were used even though they're not selected in NetworkManager. You should check {nameof(UseWebSockets)}', on the Unity Transport component, to silence this warning.");
+                driver = NetworkDriver.Create(new WebSocketNetworkInterface(), m_NetworkSettings);
+#else
+                driver = NetworkDriver.Create(new UDPNetworkInterface(), m_NetworkSettings);
+#endif
+            }
+#else
+            driver = NetworkDriver.Create(m_NetworkSettings);
+#endif
+
+#if MULTIPLAYER_TOOLS_1_0_0_PRE_7 && UTP_TRANSPORT_2_0_ABOVE
+            driver.RegisterPipelineStage(new NetworkMetricsPipelineStage());
+#endif
+
+#if !UTP_TRANSPORT_2_0_ABOVE
+            SetupPipelinesForUtp1(driver,
+                out unreliableFragmentedPipeline,
+                out unreliableSequencedFragmentedPipeline,
+                out reliableSequencedPipeline);
+#else
+            SetupPipelinesForUtp2(driver,
+                out unreliableFragmentedPipeline,
+                out unreliableSequencedFragmentedPipeline,
+                out reliableSequencedPipeline);
+#endif
+        }
+
+#if !UTP_TRANSPORT_2_0_ABOVE
+        private void SetupPipelinesForUtp1(NetworkDriver driver,
+            out NetworkPipeline unreliableFragmentedPipeline,
+            out NetworkPipeline unreliableSequencedFragmentedPipeline,
+            out NetworkPipeline reliableSequencedPipeline)
+        {
 #if UNITY_EDITOR || DEVELOPMENT_BUILD
             if (DebugSimulator.PacketDelayMS > 0 || DebugSimulator.PacketDropRate > 0)
             {
@@ -1355,7 +1557,7 @@ namespace Unity.Netcode.Transports.UTP
                     typeof(SimulatorPipelineStage),
                     typeof(SimulatorPipelineStageInSend)
 #if MULTIPLAYER_TOOLS_1_0_0_PRE_7
-                    ,typeof(NetworkMetricsPipelineStage)
+                    , typeof(NetworkMetricsPipelineStage)
 #endif
                 );
                 reliableSequencedPipeline = driver.CreatePipeline(
@@ -1363,7 +1565,7 @@ namespace Unity.Netcode.Transports.UTP
                     typeof(SimulatorPipelineStage),
                     typeof(SimulatorPipelineStageInSend)
 #if MULTIPLAYER_TOOLS_1_0_0_PRE_7
-                    ,typeof(NetworkMetricsPipelineStage)
+                    , typeof(NetworkMetricsPipelineStage)
 #endif
                 );
             }
@@ -1373,25 +1575,63 @@ namespace Unity.Netcode.Transports.UTP
                 unreliableFragmentedPipeline = driver.CreatePipeline(
                     typeof(FragmentationPipelineStage)
 #if MULTIPLAYER_TOOLS_1_0_0_PRE_7
-                    ,typeof(NetworkMetricsPipelineStage)
+                    , typeof(NetworkMetricsPipelineStage)
 #endif
                 );
                 unreliableSequencedFragmentedPipeline = driver.CreatePipeline(
                     typeof(FragmentationPipelineStage),
                     typeof(UnreliableSequencedPipelineStage)
 #if MULTIPLAYER_TOOLS_1_0_0_PRE_7
-                    ,typeof(NetworkMetricsPipelineStage)
+                    , typeof(NetworkMetricsPipelineStage)
 #endif
                 );
                 reliableSequencedPipeline = driver.CreatePipeline(
                     typeof(ReliableSequencedPipelineStage)
 #if MULTIPLAYER_TOOLS_1_0_0_PRE_7
-                    ,typeof(NetworkMetricsPipelineStage)
+                    , typeof(NetworkMetricsPipelineStage)
 #endif
                 );
             }
         }
+#else
+        private void SetupPipelinesForUtp2(NetworkDriver driver,
+            out NetworkPipeline unreliableFragmentedPipeline,
+            out NetworkPipeline unreliableSequencedFragmentedPipeline,
+            out NetworkPipeline reliableSequencedPipeline)
+        {
 
+            unreliableFragmentedPipeline = driver.CreatePipeline(
+                typeof(FragmentationPipelineStage)
+#if UNITY_MP_TOOLS_NETSIM_IMPLEMENTATION_ENABLED
+                , typeof(SimulatorPipelineStage)
+#endif
+#if MULTIPLAYER_TOOLS_1_0_0_PRE_7
+                , typeof(NetworkMetricsPipelineStage)
+#endif
+            );
+
+            unreliableSequencedFragmentedPipeline = driver.CreatePipeline(
+                typeof(FragmentationPipelineStage),
+                typeof(UnreliableSequencedPipelineStage)
+#if UNITY_MP_TOOLS_NETSIM_IMPLEMENTATION_ENABLED
+                , typeof(SimulatorPipelineStage)
+#endif
+#if MULTIPLAYER_TOOLS_1_0_0_PRE_7
+                , typeof(NetworkMetricsPipelineStage)
+#endif
+            );
+
+            reliableSequencedPipeline = driver.CreatePipeline(
+                typeof(ReliableSequencedPipelineStage)
+#if UNITY_MP_TOOLS_NETSIM_IMPLEMENTATION_ENABLED
+                , typeof(SimulatorPipelineStage)
+#endif
+#if MULTIPLAYER_TOOLS_1_0_0_PRE_7
+                , typeof(NetworkMetricsPipelineStage)
+#endif
+            );
+        }
+#endif
         // -------------- Utility Types -------------------------------------------------------------------------------
 
 

Runtime/com.unity.netcode.runtime.asmdef

@@ -30,6 +30,11 @@
             "name": "com.unity.multiplayer.tools",
             "expression": "1.0.0-pre.7",
             "define": "MULTIPLAYER_TOOLS_1_0_0_PRE_7"
+        },
+        {
+            "name": "com.unity.transport",
+            "expression": "2.0.0-exp",
+            "define": "UTP_TRANSPORT_2_0_ABOVE"
         }
     ]
 }

TestHelpers/Runtime/DebugNetworkHooks.cs

@@ -0,0 +1,63 @@
+using System;
+using UnityEngine;
+
+namespace Unity.Netcode.TestHelpers.Runtime
+{
+    internal class DebugNetworkHooks : INetworkHooks
+    {
+        public void OnBeforeSendMessage<T>(ulong clientId, ref T message, NetworkDelivery delivery) where T : INetworkMessage
+        {
+        }
+
+        public void OnAfterSendMessage<T>(ulong clientId, ref T message, NetworkDelivery delivery, int messageSizeBytes) where T : INetworkMessage
+        {
+            Debug.Log($"Sending message of type {typeof(T).Name} to {clientId} ({messageSizeBytes} bytes)");
+        }
+
+        public void OnBeforeReceiveMessage(ulong senderId, Type messageType, int messageSizeBytes)
+        {
+            Debug.Log($"Receiving message of type {messageType.Name} from {senderId}");
+        }
+
+        public void OnAfterReceiveMessage(ulong senderId, Type messageType, int messageSizeBytes)
+        {
+        }
+
+        public void OnBeforeSendBatch(ulong clientId, int messageCount, int batchSizeInBytes, NetworkDelivery delivery)
+        {
+            Debug.Log($"==> Sending a batch of {messageCount} messages ({batchSizeInBytes} bytes) to {clientId} ({delivery})");
+        }
+
+        public void OnAfterSendBatch(ulong clientId, int messageCount, int batchSizeInBytes, NetworkDelivery delivery)
+        {
+        }
+
+        public void OnBeforeReceiveBatch(ulong senderId, int messageCount, int batchSizeInBytes)
+        {
+            Debug.Log($"<== Receiving a batch of {messageCount} messages ({batchSizeInBytes} bytes) from {senderId}");
+        }
+
+        public void OnAfterReceiveBatch(ulong senderId, int messageCount, int batchSizeInBytes)
+        {
+        }
+
+        public bool OnVerifyCanSend(ulong destinationId, Type messageType, NetworkDelivery delivery)
+        {
+            return true;
+        }
+
+        public bool OnVerifyCanReceive(ulong senderId, Type messageType, FastBufferReader messageContent, ref NetworkContext context)
+        {
+            return true;
+        }
+
+        public void OnBeforeHandleMessage<T>(ref T message, ref NetworkContext context) where T : INetworkMessage
+        {
+            Debug.Log($"Handling a message of type {typeof(T).Name}");
+        }
+
+        public void OnAfterHandleMessage<T>(ref T message, ref NetworkContext context) where T : INetworkMessage
+        {
+        }
+    }
+}

TestHelpers/Runtime/DebugNetworkHooks.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: b5f8098e713443eeba116a25de551cf8
+timeCreated: 1666626883

TestHelpers/Runtime/IntegrationTestSceneHandler.cs

@@ -48,7 +48,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
             public JobTypes JobType;
             public string SceneName;
             public Scene Scene;
-            public ISceneManagerHandler.SceneEventAction SceneAction;
+            public SceneEventProgress SceneEventProgress;
             public IntegrationTestSceneHandler IntegrationTestSceneHandler;
         }
 
@@ -106,7 +106,8 @@ namespace Unity.Netcode.TestHelpers.Runtime
 
             SceneManager.sceneLoaded += SceneManager_sceneLoaded;
             // We always load additively for all scenes during integration tests
-            SceneManager.LoadSceneAsync(queuedSceneJob.SceneName, LoadSceneMode.Additive);
+            var asyncOperation = SceneManager.LoadSceneAsync(queuedSceneJob.SceneName, LoadSceneMode.Additive);
+            queuedSceneJob.SceneEventProgress.SetAsyncOperation(asyncOperation);
 
             // Wait for it to finish
             while (queuedSceneJob.JobType != QueuedSceneJob.JobTypes.Completed)
@@ -114,7 +115,6 @@ namespace Unity.Netcode.TestHelpers.Runtime
                 yield return s_WaitForSeconds;
             }
             yield return s_WaitForSeconds;
-            CurrentQueuedSceneJob.SceneAction.Invoke();
         }
 
         /// <summary>
@@ -147,7 +147,12 @@ namespace Unity.Netcode.TestHelpers.Runtime
         private static void ProcessInSceneObjects(Scene scene, NetworkManager networkManager)
         {
             // Get all in-scene placed NeworkObjects that were instantiated when this scene loaded
+#if UNITY_2023_1_OR_NEWER
+            var inSceneNetworkObjects = Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID).Where((c) => c.IsSceneObject != false && c.GetSceneOriginHandle() == scene.handle);
+#else
             var inSceneNetworkObjects = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsSceneObject != false && c.GetSceneOriginHandle() == scene.handle);
+#endif
+
             foreach (var sobj in inSceneNetworkObjects)
             {
                 if (sobj.NetworkManagerOwner != networkManager)
@@ -176,7 +181,8 @@ namespace Unity.Netcode.TestHelpers.Runtime
             SceneManager.sceneUnloaded += SceneManager_sceneUnloaded;
             if (queuedSceneJob.Scene.IsValid() && queuedSceneJob.Scene.isLoaded && !queuedSceneJob.Scene.name.Contains(NetcodeIntegrationTestHelpers.FirstPartOfTestRunnerSceneName))
             {
-                SceneManager.UnloadSceneAsync(queuedSceneJob.Scene);
+                var asyncOperation = SceneManager.UnloadSceneAsync(queuedSceneJob.Scene);
+                queuedSceneJob.SceneEventProgress.SetAsyncOperation(asyncOperation);
             }
             else
             {
@@ -188,7 +194,6 @@ namespace Unity.Netcode.TestHelpers.Runtime
             {
                 yield return s_WaitForSeconds;
             }
-            CurrentQueuedSceneJob.SceneAction.Invoke();
         }
 
         /// <summary>
@@ -246,7 +251,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
         /// <summary>
         /// Server always loads like it normally would
         /// </summary>
-        public AsyncOperation GenericLoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, ISceneManagerHandler.SceneEventAction sceneEventAction)
+        public AsyncOperation GenericLoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, SceneEventProgress sceneEventProgress)
         {
             m_ServerSceneBeingLoaded = sceneName;
             if (NetcodeIntegrationTest.IsRunning)
@@ -254,8 +259,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
                 SceneManager.sceneLoaded += Sever_SceneLoaded;
             }
             var operation = SceneManager.LoadSceneAsync(sceneName, loadSceneMode);
-
-            operation.completed += new Action<AsyncOperation>(asyncOp2 => { sceneEventAction.Invoke(); });
+            sceneEventProgress.SetAsyncOperation(operation);
             return operation;
         }
 
@@ -271,39 +275,39 @@ namespace Unity.Netcode.TestHelpers.Runtime
         /// <summary>
         /// Server always unloads like it normally would
         /// </summary>
-        public AsyncOperation GenericUnloadSceneAsync(Scene scene, ISceneManagerHandler.SceneEventAction sceneEventAction)
+        public AsyncOperation GenericUnloadSceneAsync(Scene scene, SceneEventProgress sceneEventProgress)
         {
             var operation = SceneManager.UnloadSceneAsync(scene);
-            operation.completed += new Action<AsyncOperation>(asyncOp2 => { sceneEventAction.Invoke(); });
+            sceneEventProgress.SetAsyncOperation(operation);
             return operation;
         }
 
 
-        public AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, ISceneManagerHandler.SceneEventAction sceneEventAction)
+        public AsyncOperation LoadSceneAsync(string sceneName, LoadSceneMode loadSceneMode, SceneEventProgress sceneEventProgress)
         {
             // Server and non NetcodeIntegrationTest tests use the generic load scene method
             if (!NetcodeIntegrationTest.IsRunning)
             {
-                return GenericLoadSceneAsync(sceneName, loadSceneMode, sceneEventAction);
+                return GenericLoadSceneAsync(sceneName, loadSceneMode, sceneEventProgress);
             }
             else // NetcodeIntegrationTest Clients always get added to the jobs queue
             {
-                AddJobToQueue(new QueuedSceneJob() { IntegrationTestSceneHandler = this, SceneName = sceneName, SceneAction = sceneEventAction, JobType = QueuedSceneJob.JobTypes.Loading });
+                AddJobToQueue(new QueuedSceneJob() { IntegrationTestSceneHandler = this, SceneName = sceneName, SceneEventProgress = sceneEventProgress, JobType = QueuedSceneJob.JobTypes.Loading });
             }
 
             return null;
         }
 
-        public AsyncOperation UnloadSceneAsync(Scene scene, ISceneManagerHandler.SceneEventAction sceneEventAction)
+        public AsyncOperation UnloadSceneAsync(Scene scene, SceneEventProgress sceneEventProgress)
         {
             // Server and non NetcodeIntegrationTest tests use the generic unload scene method
             if (!NetcodeIntegrationTest.IsRunning)
             {
-                return GenericUnloadSceneAsync(scene, sceneEventAction);
+                return GenericUnloadSceneAsync(scene, sceneEventProgress);
             }
             else // NetcodeIntegrationTest Clients always get added to the jobs queue
             {
-                AddJobToQueue(new QueuedSceneJob() { IntegrationTestSceneHandler = this, Scene = scene, SceneAction = sceneEventAction, JobType = QueuedSceneJob.JobTypes.Unloading });
+                AddJobToQueue(new QueuedSceneJob() { IntegrationTestSceneHandler = this, Scene = scene, SceneEventProgress = sceneEventProgress, JobType = QueuedSceneJob.JobTypes.Unloading });
             }
             // This is OK to return a "nothing" AsyncOperation since we are simulating client loading
             return null;

TestHelpers/Runtime/MessageHooks.cs

@@ -4,14 +4,22 @@ namespace Unity.Netcode.TestHelpers.Runtime
 {
     internal class MessageHooks : INetworkHooks
     {
-        public bool IsWaiting;
-        public delegate bool MessageReceiptCheck(object receivedMessage);
+        public bool IsWaiting = true;
+        public delegate bool MessageReceiptCheck(Type receivedMessageType);
         public MessageReceiptCheck ReceiptCheck;
+        public delegate bool MessageHandleCheck(object receivedMessage);
+        public MessageHandleCheck HandleCheck;
 
-        public static bool CheckForMessageOfType<T>(object receivedMessage) where T : INetworkMessage
+        public static bool CurrentMessageHasTriggerdAHook = false;
+
+        public static bool CheckForMessageOfTypeHandled<T>(object receivedMessage) where T : INetworkMessage
         {
             return receivedMessage is T;
         }
+        public static bool CheckForMessageOfTypeReceived<T>(Type receivedMessageType) where T : INetworkMessage
+        {
+            return receivedMessageType == typeof(T);
+        }
 
         public void OnBeforeSendMessage<T>(ulong clientId, ref T message, NetworkDelivery delivery) where T : INetworkMessage
         {
@@ -23,10 +31,24 @@ namespace Unity.Netcode.TestHelpers.Runtime
 
         public void OnBeforeReceiveMessage(ulong senderId, Type messageType, int messageSizeBytes)
         {
+            // The way the system works, it goes through all hooks and calls OnBeforeHandleMessage, then handles the message,
+            // then goes thorugh all hooks and calls OnAfterHandleMessage.
+            // This ensures each message only manages to activate a single message hook - because we know that only
+            // one message will ever be handled between OnBeforeHandleMessage and OnAfterHandleMessage,
+            // we can reset the flag here, and then in OnAfterHandleMessage, the moment the message matches a hook,
+            // it'll flip this flag back on, and then other hooks will stop checking that message.
+            // Without this flag, waiting for 10 messages of the same type isn't possible - all 10 hooks would get
+            // tripped by the first message.
+            CurrentMessageHasTriggerdAHook = false;
         }
 
         public void OnAfterReceiveMessage(ulong senderId, Type messageType, int messageSizeBytes)
         {
+            if (!CurrentMessageHasTriggerdAHook && IsWaiting && ReceiptCheck != null && ReceiptCheck.Invoke(messageType))
+            {
+                IsWaiting = false;
+                CurrentMessageHasTriggerdAHook = true;
+            }
         }
 
         public void OnBeforeSendBatch(ulong clientId, int messageCount, int batchSizeInBytes, NetworkDelivery delivery)
@@ -57,13 +79,23 @@ namespace Unity.Netcode.TestHelpers.Runtime
 
         public void OnBeforeHandleMessage<T>(ref T message, ref NetworkContext context) where T : INetworkMessage
         {
+            // The way the system works, it goes through all hooks and calls OnBeforeHandleMessage, then handles the message,
+            // then goes thorugh all hooks and calls OnAfterHandleMessage.
+            // This ensures each message only manages to activate a single message hook - because we know that only
+            // one message will ever be handled between OnBeforeHandleMessage and OnAfterHandleMessage,
+            // we can reset the flag here, and then in OnAfterHandleMessage, the moment the message matches a hook,
+            // it'll flip this flag back on, and then other hooks will stop checking that message.
+            // Without this flag, waiting for 10 messages of the same type isn't possible - all 10 hooks would get
+            // tripped by the first message.
+            CurrentMessageHasTriggerdAHook = false;
         }
 
         public void OnAfterHandleMessage<T>(ref T message, ref NetworkContext context) where T : INetworkMessage
         {
-            if (IsWaiting && (ReceiptCheck == null || ReceiptCheck.Invoke(message)))
+            if (!CurrentMessageHasTriggerdAHook && IsWaiting && HandleCheck != null && HandleCheck.Invoke(message))
             {
                 IsWaiting = false;
+                CurrentMessageHasTriggerdAHook = true;
             }
         }
     }

TestHelpers/Runtime/MessageHooksConditional.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using NUnit.Framework;
@@ -38,7 +39,10 @@ namespace Unity.Netcode.TestHelpers.Runtime
 
             if (AllMessagesReceived)
             {
-                return AllMessagesReceived;
+                foreach (var entry in m_MessageHookEntries)
+                {
+                    entry.RemoveHook();
+                }
             }
 
             return AllMessagesReceived;
@@ -63,18 +67,34 @@ namespace Unity.Netcode.TestHelpers.Runtime
         }
     }
 
+    public enum ReceiptType
+    {
+        Received,
+        Handled
+    }
+
     public class MessageHookEntry
     {
         internal MessageHooks MessageHooks;
         protected NetworkManager m_NetworkManager;
         private MessageHooks.MessageReceiptCheck m_MessageReceiptCheck;
+        private MessageHooks.MessageHandleCheck m_MessageHandleCheck;
         internal string MessageType;
+        private ReceiptType m_ReceiptType;
 
         public void Initialize()
         {
-            Assert.IsNotNull(m_MessageReceiptCheck, $"{nameof(m_MessageReceiptCheck)} is null, did you forget to initialize?");
             MessageHooks = new MessageHooks();
-            MessageHooks.ReceiptCheck = m_MessageReceiptCheck;
+            if (m_ReceiptType == ReceiptType.Handled)
+            {
+                Assert.IsNotNull(m_MessageHandleCheck, $"{nameof(m_MessageHandleCheck)} is null, did you forget to initialize?");
+                MessageHooks.HandleCheck = m_MessageHandleCheck;
+            }
+            else
+            {
+                Assert.IsNotNull(m_MessageReceiptCheck, $"{nameof(m_MessageReceiptCheck)} is null, did you forget to initialize?");
+                MessageHooks.ReceiptCheck = m_MessageReceiptCheck;
+            }
             Assert.IsNotNull(m_NetworkManager.MessagingSystem, $"{nameof(NetworkManager.MessagingSystem)} is null! Did you forget to start first?");
             m_NetworkManager.MessagingSystem.Hook(MessageHooks);
         }
@@ -82,14 +102,46 @@ namespace Unity.Netcode.TestHelpers.Runtime
         internal void AssignMessageType<T>() where T : INetworkMessage
         {
             MessageType = typeof(T).Name;
-            m_MessageReceiptCheck = MessageHooks.CheckForMessageOfType<T>;
+            if (m_ReceiptType == ReceiptType.Handled)
+            {
+                m_MessageHandleCheck = MessageHooks.CheckForMessageOfTypeHandled<T>;
+            }
+            else
+            {
+                m_MessageReceiptCheck = MessageHooks.CheckForMessageOfTypeReceived<T>;
+            }
             Initialize();
         }
 
-        public MessageHookEntry(NetworkManager networkManager)
+        internal void RemoveHook()
+        {
+            m_NetworkManager.MessagingSystem.Unhook(MessageHooks);
+        }
+
+        internal void AssignMessageType(Type type)
+        {
+            MessageType = type.Name;
+            if (m_ReceiptType == ReceiptType.Handled)
+            {
+                m_MessageHandleCheck = (message) =>
+                {
+                    return message.GetType() == type;
+                };
+            }
+            else
+            {
+                m_MessageReceiptCheck = (messageType) =>
+                {
+                    return messageType == type;
+                };
+            }
+            Initialize();
+        }
+
+        public MessageHookEntry(NetworkManager networkManager, ReceiptType type = ReceiptType.Handled)
         {
             m_NetworkManager = networkManager;
+            m_ReceiptType = type;
         }
     }
 }
-

TestHelpers/Runtime/Metrics/RpcTestComponent.cs

@@ -14,7 +14,7 @@ namespace Unity.Netcode.TestHelpers.Runtime.Metrics
         }
 
         [ClientRpc]
-        public void MyClientRpc()
+        public void MyClientRpc(ClientRpcParams rpcParams = default)
         {
             OnClientRpcAction?.Invoke();
         }

TestHelpers/Runtime/Metrics/WaitForEventMetricValues.cs

@@ -1,10 +1,6 @@
 #if MULTIPLAYER_TOOLS
-using System;
-using System.Collections;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Linq;
-using NUnit.Framework;
 using Unity.Multiplayer.Tools.MetricTypes;
 using Unity.Multiplayer.Tools.NetStats;
 
@@ -12,10 +8,11 @@ namespace Unity.Netcode.TestHelpers.Runtime.Metrics
 {
     internal class WaitForEventMetricValues<TMetric> : WaitForMetricValues<TMetric>
     {
-        IReadOnlyCollection<TMetric> m_EventValues;
+        private IReadOnlyCollection<TMetric> m_EventValues;
 
         public delegate bool EventFilter(TMetric metric);
-        EventFilter m_EventFilterDelegate;
+
+        private EventFilter m_EventFilterDelegate;
 
         public WaitForEventMetricValues(IMetricDispatcher dispatcher, DirectionalMetricInfo directionalMetricName)
             : base(dispatcher, directionalMetricName)

TestHelpers/Runtime/NetcodeIntegrationTest.cs

@@ -7,7 +7,7 @@ using UnityEngine;
 using UnityEngine.SceneManagement;
 using UnityEngine.TestTools;
 using System.Runtime.CompilerServices;
-
+using Unity.Netcode.RuntimeTests;
 using Object = UnityEngine.Object;
 
 namespace Unity.Netcode.TestHelpers.Runtime
@@ -23,7 +23,9 @@ namespace Unity.Netcode.TestHelpers.Runtime
         /// </summary>
         internal static bool IsRunning { get; private set; }
         protected static TimeoutHelper s_GlobalTimeoutHelper = new TimeoutHelper(8.0f);
-        protected static WaitForSeconds s_DefaultWaitForTick = new WaitForSeconds(1.0f / k_DefaultTickRate);
+        protected static WaitForSecondsRealtime s_DefaultWaitForTick = new WaitForSecondsRealtime(1.0f / k_DefaultTickRate);
+
+        public NetcodeLogAssert NetcodeLogAssert;
 
         /// <summary>
         /// Registered list of all NetworkObjects spawned.
@@ -129,6 +131,18 @@ namespace Unity.Netcode.TestHelpers.Runtime
 
         protected bool m_EnableVerboseDebug { get; set; }
 
+        /// <summary>
+        /// When set to true, this will bypass the entire
+        /// wait for clients to connect process.
+        /// </summary>
+        /// <remarks>
+        /// CAUTION:
+        /// Setting this to true will bypass other helper
+        /// identification related code, so this should only
+        /// be used for connection failure oriented testing
+        /// </remarks>
+        protected bool m_BypassConnectionTimeout { get; set; }
+
         /// <summary>
         /// Used to display the various integration test
         /// stages and can be used to log verbose information
@@ -207,6 +221,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
         {
             VerboseDebug($"Entering {nameof(SetUp)}");
 
+            NetcodeLogAssert = new NetcodeLogAssert();
             yield return OnSetup();
             if (m_NetworkManagerInstatiationMode == NetworkManagerInstatiationMode.AllTests && m_ServerNetworkManager == null ||
                 m_NetworkManagerInstatiationMode == NetworkManagerInstatiationMode.PerTest)
@@ -259,16 +274,6 @@ namespace Unity.Netcode.TestHelpers.Runtime
             CreateServerAndClients(NumberOfClients);
         }
 
-        protected virtual void OnNewClientCreated(NetworkManager networkManager)
-        {
-
-        }
-
-        protected virtual void OnNewClientStartedAndConnected(NetworkManager networkManager)
-        {
-
-        }
-
         private void AddRemoveNetworkManager(NetworkManager networkManager, bool addNetworkManager)
         {
             var clientNetworkManagersList = new List<NetworkManager>(m_ClientNetworkManagers);
@@ -284,6 +289,37 @@ namespace Unity.Netcode.TestHelpers.Runtime
             m_NumberOfClients = clientNetworkManagersList.Count;
         }
 
+        /// <summary>
+        /// CreateAndStartNewClient Only
+        /// Invoked when the newly created client has been created
+        /// </summary>
+        protected virtual void OnNewClientCreated(NetworkManager networkManager)
+        {
+
+        }
+
+        /// <summary>
+        /// CreateAndStartNewClient Only
+        /// Invoked when the newly created client has been created and started
+        /// </summary>
+        protected virtual void OnNewClientStarted(NetworkManager networkManager)
+        {
+        }
+
+        /// <summary>
+        /// CreateAndStartNewClient Only
+        /// Invoked when the newly created client has been created, started, and connected
+        /// to the server-host.
+        /// </summary>
+        protected virtual void OnNewClientStartedAndConnected(NetworkManager networkManager)
+        {
+
+        }
+
+        /// <summary>
+        /// This will create, start, and connect a new client while in the middle of an
+        /// integration test.
+        /// </summary>
         protected IEnumerator CreateAndStartNewClient()
         {
             var networkManager = NetcodeIntegrationTestHelpers.CreateNewClient(m_ClientNetworkManagers.Length);
@@ -294,9 +330,20 @@ namespace Unity.Netcode.TestHelpers.Runtime
             OnNewClientCreated(networkManager);
 
             NetcodeIntegrationTestHelpers.StartOneClient(networkManager);
+
+            if (LogAllMessages)
+            {
+                networkManager.MessagingSystem.Hook(new DebugNetworkHooks());
+            }
+
             AddRemoveNetworkManager(networkManager, true);
+
+            OnNewClientStarted(networkManager);
+
             // Wait for the new client to connect
             yield return WaitForClientsConnectedOrTimeOut();
+
+            OnNewClientStartedAndConnected(networkManager);
             if (s_GlobalTimeoutHelper.TimedOut)
             {
                 AddRemoveNetworkManager(networkManager, false);
@@ -307,6 +354,9 @@ namespace Unity.Netcode.TestHelpers.Runtime
             VerboseDebug($"[{networkManager.name}] Created and connected!");
         }
 
+        /// <summary>
+        /// This will stop a client while in the middle of an integration test
+        /// </summary>
         protected IEnumerator StopOneClient(NetworkManager networkManager, bool destroy = false)
         {
             NetcodeIntegrationTestHelpers.StopOneClient(networkManager, destroy);
@@ -336,7 +386,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
 
             if (m_ServerNetworkManager != null)
             {
-                s_DefaultWaitForTick = new WaitForSeconds(1.0f / m_ServerNetworkManager.NetworkConfig.TickRate);
+                s_DefaultWaitForTick = new WaitForSecondsRealtime(1.0f / m_ServerNetworkManager.NetworkConfig.TickRate);
             }
 
             // Set the player prefab for the server and clients
@@ -386,8 +436,19 @@ namespace Unity.Netcode.TestHelpers.Runtime
             networkManager.name = $"NetworkManager - Client - {networkManager.LocalClientId}";
             Assert.NotNull(networkManager.LocalClient.PlayerObject, $"{nameof(StartServerAndClients)} detected that client {networkManager.LocalClientId} does not have an assigned player NetworkObject!");
 
+            // Go ahead and create an entry for this new client
+            if (!m_PlayerNetworkObjects.ContainsKey(networkManager.LocalClientId))
+            {
+                m_PlayerNetworkObjects.Add(networkManager.LocalClientId, new Dictionary<ulong, NetworkObject>());
+            }
+
+#if UNITY_2023_1_OR_NEWER
             // Get all player instances for the current client NetworkManager instance
-            var clientPlayerClones = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsPlayerObject && c.OwnerClientId == networkManager.LocalClientId);
+            var clientPlayerClones = Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.None).Where((c) => c.IsPlayerObject && c.OwnerClientId == networkManager.LocalClientId).ToList();
+#else
+            // Get all player instances for the current client NetworkManager instance
+            var clientPlayerClones = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsPlayerObject && c.OwnerClientId == networkManager.LocalClientId).ToList();
+#endif
             // Add this player instance to each client player entry
             foreach (var playerNetworkObject in clientPlayerClones)
             {
@@ -401,6 +462,20 @@ namespace Unity.Netcode.TestHelpers.Runtime
                     m_PlayerNetworkObjects[playerNetworkObject.NetworkManager.LocalClientId].Add(networkManager.LocalClientId, playerNetworkObject);
                 }
             }
+#if UNITY_2023_1_OR_NEWER
+            // For late joining clients, add the remaining (if any) cloned versions of each client's player
+            clientPlayerClones = Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.None).Where((c) => c.IsPlayerObject && c.NetworkManager == networkManager).ToList();
+#else
+            // For late joining clients, add the remaining (if any) cloned versions of each client's player
+            clientPlayerClones = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsPlayerObject && c.NetworkManager == networkManager).ToList();
+#endif
+            foreach (var playerNetworkObject in clientPlayerClones)
+            {
+                if (!m_PlayerNetworkObjects[networkManager.LocalClientId].ContainsKey(playerNetworkObject.OwnerClientId))
+                {
+                    m_PlayerNetworkObjects[networkManager.LocalClientId].Add(playerNetworkObject.OwnerClientId, playerNetworkObject);
+                }
+            }
         }
 
         protected void ClientNetworkManagerPostStartInit()
@@ -413,7 +488,11 @@ namespace Unity.Netcode.TestHelpers.Runtime
             }
             if (m_UseHost)
             {
+#if UNITY_2023_1_OR_NEWER
+                var clientSideServerPlayerClones = Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.None).Where((c) => c.IsPlayerObject && c.OwnerClientId == m_ServerNetworkManager.LocalClientId);
+#else
                 var clientSideServerPlayerClones = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsPlayerObject && c.OwnerClientId == m_ServerNetworkManager.LocalClientId);
+#endif
                 foreach (var playerNetworkObject in clientSideServerPlayerClones)
                 {
                     // When the server is not the host this needs to be done
@@ -429,6 +508,8 @@ namespace Unity.Netcode.TestHelpers.Runtime
             }
         }
 
+        protected virtual bool LogAllMessages => false;
+
         /// <summary>
         /// This starts the server and clients as long as <see cref="CanStartServerAndClients"/>
         /// returns true.
@@ -447,36 +528,51 @@ namespace Unity.Netcode.TestHelpers.Runtime
                     Assert.Fail("Failed to start instances");
                 }
 
+                if (LogAllMessages)
+                {
+                    EnableMessageLogging();
+                }
+
                 RegisterSceneManagerHandler();
 
                 // Notification that the server and clients have been started
                 yield return OnStartedServerAndClients();
 
-                // Wait for all clients to connect
-                yield return WaitForClientsConnectedOrTimeOut();
-                AssertOnTimeout($"{nameof(StartServerAndClients)} timed out waiting for all clients to be connected!");
-
-                if (m_UseHost || m_ServerNetworkManager.IsHost)
+                // When true, we skip everything else (most likely a connection oriented test)
+                if (!m_BypassConnectionTimeout)
                 {
-                    // Add the server player instance to all m_ClientSidePlayerNetworkObjects entries
-                    var serverPlayerClones = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsPlayerObject && c.OwnerClientId == m_ServerNetworkManager.LocalClientId);
-                    foreach (var playerNetworkObject in serverPlayerClones)
+                    // Wait for all clients to connect
+                    yield return WaitForClientsConnectedOrTimeOut();
+
+                    AssertOnTimeout($"{nameof(StartServerAndClients)} timed out waiting for all clients to be connected!");
+
+                    if (m_UseHost || m_ServerNetworkManager.IsHost)
                     {
-                        if (!m_PlayerNetworkObjects.ContainsKey(playerNetworkObject.NetworkManager.LocalClientId))
+#if UNITY_2023_1_OR_NEWER
+                        // Add the server player instance to all m_ClientSidePlayerNetworkObjects entries
+                        var serverPlayerClones = Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.None).Where((c) => c.IsPlayerObject && c.OwnerClientId == m_ServerNetworkManager.LocalClientId);
+#else
+                        // Add the server player instance to all m_ClientSidePlayerNetworkObjects entries
+                        var serverPlayerClones = Object.FindObjectsOfType<NetworkObject>().Where((c) => c.IsPlayerObject && c.OwnerClientId == m_ServerNetworkManager.LocalClientId);
+#endif
+                        foreach (var playerNetworkObject in serverPlayerClones)
                         {
-                            m_PlayerNetworkObjects.Add(playerNetworkObject.NetworkManager.LocalClientId, new Dictionary<ulong, NetworkObject>());
+                            if (!m_PlayerNetworkObjects.ContainsKey(playerNetworkObject.NetworkManager.LocalClientId))
+                            {
+                                m_PlayerNetworkObjects.Add(playerNetworkObject.NetworkManager.LocalClientId, new Dictionary<ulong, NetworkObject>());
+                            }
+                            m_PlayerNetworkObjects[playerNetworkObject.NetworkManager.LocalClientId].Add(m_ServerNetworkManager.LocalClientId, playerNetworkObject);
                         }
-                        m_PlayerNetworkObjects[playerNetworkObject.NetworkManager.LocalClientId].Add(m_ServerNetworkManager.LocalClientId, playerNetworkObject);
                     }
+
+                    ClientNetworkManagerPostStartInit();
+
+                    // Notification that at this time the server and client(s) are instantiated,
+                    // started, and connected on both sides.
+                    yield return OnServerAndClientsConnected();
+
+                    VerboseDebug($"Exiting {nameof(StartServerAndClients)}");
                 }
-
-                ClientNetworkManagerPostStartInit();
-
-                // Notification that at this time the server and client(s) are instantiated,
-                // started, and connected on both sides.
-                yield return OnServerAndClientsConnected();
-
-                VerboseDebug($"Exiting {nameof(StartServerAndClients)}");
             }
         }
 
@@ -571,7 +667,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
             UnloadRemainingScenes();
 
             // reset the m_ServerWaitForTick for the next test to initialize
-            s_DefaultWaitForTick = new WaitForSeconds(1.0f / k_DefaultTickRate);
+            s_DefaultWaitForTick = new WaitForSecondsRealtime(1.0f / k_DefaultTickRate);
             VerboseDebug($"Exiting {nameof(ShutdownAndCleanUp)}");
         }
 
@@ -596,6 +692,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
             }
 
             VerboseDebug($"Exiting {nameof(TearDown)}");
+            NetcodeLogAssert.Dispose();
         }
 
         /// <summary>
@@ -647,7 +744,11 @@ namespace Unity.Netcode.TestHelpers.Runtime
         /// </summary>
         protected void DestroySceneNetworkObjects()
         {
+#if UNITY_2023_1_OR_NEWER
+            var networkObjects = Object.FindObjectsByType<NetworkObject>(FindObjectsSortMode.InstanceID);
+#else
             var networkObjects = Object.FindObjectsOfType<NetworkObject>();
+#endif
             foreach (var networkObject in networkObjects)
             {
                 // This can sometimes be null depending upon order of operations
@@ -671,6 +772,18 @@ namespace Unity.Netcode.TestHelpers.Runtime
             }
         }
 
+        /// <summary>
+        /// For debugging purposes, this will turn on verbose logging of all messages and batches sent and received
+        /// </summary>
+        protected void EnableMessageLogging()
+        {
+            m_ServerNetworkManager.MessagingSystem.Hook(new DebugNetworkHooks());
+            foreach (var client in m_ClientNetworkManagers)
+            {
+                client.MessagingSystem.Hook(new DebugNetworkHooks());
+            }
+        }
+
         /// <summary>
         /// Waits for the function condition to return true or it will time out.
         /// This will operate at the current m_ServerNetworkManager.NetworkConfig.TickRate
@@ -758,6 +871,41 @@ namespace Unity.Netcode.TestHelpers.Runtime
             yield return WaitForClientsConnectedOrTimeOut(m_ClientNetworkManagers);
         }
 
+        internal IEnumerator WaitForMessageReceived<T>(List<NetworkManager> wiatForReceivedBy, ReceiptType type = ReceiptType.Handled) where T : INetworkMessage
+        {
+            // Build our message hook entries tables so we can determine if all clients received spawn or ownership messages
+            var messageHookEntriesForSpawn = new List<MessageHookEntry>();
+            foreach (var clientNetworkManager in wiatForReceivedBy)
+            {
+                var messageHook = new MessageHookEntry(clientNetworkManager, type);
+                messageHook.AssignMessageType<T>();
+                messageHookEntriesForSpawn.Add(messageHook);
+            }
+            // Used to determine if all clients received the CreateObjectMessage
+            var hooks = new MessageHooksConditional(messageHookEntriesForSpawn);
+            yield return WaitForConditionOrTimeOut(hooks);
+            Assert.False(s_GlobalTimeoutHelper.TimedOut);
+        }
+
+        internal IEnumerator WaitForMessagesReceived(List<Type> messagesInOrder, List<NetworkManager> wiatForReceivedBy, ReceiptType type = ReceiptType.Handled)
+        {
+            // Build our message hook entries tables so we can determine if all clients received spawn or ownership messages
+            var messageHookEntriesForSpawn = new List<MessageHookEntry>();
+            foreach (var clientNetworkManager in wiatForReceivedBy)
+            {
+                foreach (var message in messagesInOrder)
+                {
+                    var messageHook = new MessageHookEntry(clientNetworkManager, type);
+                    messageHook.AssignMessageType(message);
+                    messageHookEntriesForSpawn.Add(messageHook);
+                }
+            }
+            // Used to determine if all clients received the CreateObjectMessage
+            var hooks = new MessageHooksConditional(messageHookEntriesForSpawn);
+            yield return WaitForConditionOrTimeOut(hooks);
+            Assert.False(s_GlobalTimeoutHelper.TimedOut);
+        }
+
         /// <summary>
         /// Creates a basic NetworkObject test prefab, assigns it to a new
         /// NetworkPrefab entry, and then adds it to the server and client(s)

TestHelpers/Runtime/NetcodeLogAssert.cs

@@ -0,0 +1,152 @@
+using System;
+using System.Collections.Generic;
+using System.Text.RegularExpressions;
+using NUnit.Framework;
+using UnityEngine;
+
+namespace Unity.Netcode.RuntimeTests
+{
+    public class NetcodeLogAssert
+    {
+        private struct LogData
+        {
+            public LogType LogType;
+            public string Message;
+            public string StackTrace;
+        }
+
+        private readonly object m_Lock = new object();
+        private bool m_Disposed;
+
+        private List<LogData> AllLogs { get; }
+
+        public NetcodeLogAssert()
+        {
+            AllLogs = new List<LogData>();
+            Activate();
+        }
+
+        private void Activate()
+        {
+            Application.logMessageReceivedThreaded += AddLog;
+        }
+
+        private void Deactivate()
+        {
+            Application.logMessageReceivedThreaded -= AddLog;
+        }
+
+        public void AddLog(string message, string stacktrace, LogType type)
+        {
+            lock (m_Lock)
+            {
+                var log = new LogData
+                {
+                    LogType = type,
+                    Message = message,
+                    StackTrace = stacktrace,
+                };
+
+                AllLogs.Add(log);
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (m_Disposed)
+            {
+                return;
+            }
+
+            m_Disposed = true;
+
+            if (disposing)
+            {
+                Deactivate();
+            }
+        }
+
+        public void LogWasNotReceived(LogType type, string message)
+        {
+            lock (m_Lock)
+            {
+                foreach (var logEvent in AllLogs)
+                {
+                    if (logEvent.LogType == type && message.Equals(logEvent.Message))
+                    {
+                        Assert.Fail($"Unexpected log: [{logEvent.LogType}] {logEvent.Message}");
+                    }
+                }
+            }
+        }
+
+        public void LogWasNotReceived(LogType type, Regex messageRegex)
+        {
+            lock (m_Lock)
+            {
+                foreach (var logEvent in AllLogs)
+                {
+                    if (logEvent.LogType == type && messageRegex.IsMatch(logEvent.Message))
+                    {
+                        Assert.Fail($"Unexpected log: [{logEvent.LogType}] {logEvent.Message}");
+                    }
+                }
+            }
+        }
+
+        public void LogWasReceived(LogType type, string message)
+        {
+            lock (m_Lock)
+            {
+                var found = false;
+                foreach (var logEvent in AllLogs)
+                {
+                    if (logEvent.LogType == type && message.Equals(logEvent.Message))
+                    {
+                        found = true;
+                        break;
+                    }
+                }
+
+                if (!found)
+                {
+                    Assert.Fail($"Expected log was not received: [{type}] {message}");
+                }
+            }
+        }
+
+        public void LogWasReceived(LogType type, Regex messageRegex)
+        {
+            lock (m_Lock)
+            {
+                var found = false;
+                foreach (var logEvent in AllLogs)
+                {
+                    if (logEvent.LogType == type && messageRegex.IsMatch(logEvent.Message))
+                    {
+                        found = true;
+                    }
+                }
+
+                if (!found)
+                {
+                    Assert.Fail($"Expected log was not received: [{type}] {messageRegex}");
+                }
+            }
+        }
+
+        public void Reset()
+        {
+            lock (m_Lock)
+            {
+                AllLogs.Clear();
+            }
+        }
+    }
+}

TestHelpers/Runtime/NetcodeLogAssert.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 61774c54cd14423ca4de6d56c9fd0fe8
+timeCreated: 1661800793

TestHelpers/Runtime/NetworkVariableHelper.cs

@@ -13,7 +13,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
     /// From both we can then at least determine if the value indeed changed
     /// </summary>
     /// <typeparam name="T"></typeparam>
-    public class NetworkVariableHelper<T> : NetworkVariableBaseHelper where T : unmanaged
+    public class NetworkVariableHelper<T> : NetworkVariableBaseHelper
     {
         private readonly NetworkVariable<T> m_NetworkVariable;
         public delegate void OnMyValueChangedDelegateHandler(T previous, T next);
@@ -50,7 +50,7 @@ namespace Unity.Netcode.TestHelpers.Runtime
         {
             if (previous is ValueType testValueType)
             {
-                CheckVariableChanged(previous, next);
+                CheckVariableChanged(previous as ValueType, next as ValueType);
             }
             else
             {

Tests/Editor/Build/BuildTests.cs

@@ -12,6 +12,7 @@ namespace Unity.Netcode.EditorTests
         public const string DefaultBuildScenePath = "Tests/Editor/Build/BuildTestScene.unity";
 
         [Test]
+        [Ignore("Disabling this test on release/1.2.0 branch due to Burst failures caused when running with upm ci")]
         public void BasicBuildTest()
         {
             var execAssembly = Assembly.GetExecutingAssembly();

Tests/Editor/DisconnectMessageTests.cs

@@ -0,0 +1,56 @@
+using NUnit.Framework;
+using Unity.Collections;
+
+namespace Unity.Netcode.EditorTests
+{
+    public class DisconnectMessageTests
+    {
+        [Test]
+        public void EmptyDisconnectReason()
+        {
+            var networkContext = new NetworkContext();
+            var writer = new FastBufferWriter(20, Allocator.Temp, 20);
+            var msg = new DisconnectReasonMessage();
+            msg.Reason = string.Empty;
+            msg.Serialize(writer, msg.Version);
+
+            var fbr = new FastBufferReader(writer, Allocator.Temp);
+            var recvMsg = new DisconnectReasonMessage();
+            recvMsg.Deserialize(fbr, ref networkContext, msg.Version);
+
+            Assert.IsEmpty(recvMsg.Reason);
+        }
+
+        [Test]
+        public void DisconnectReason()
+        {
+            var networkContext = new NetworkContext();
+            var writer = new FastBufferWriter(20, Allocator.Temp, 20);
+            var msg = new DisconnectReasonMessage();
+            msg.Reason = "Foo";
+            msg.Serialize(writer, msg.Version);
+
+            var fbr = new FastBufferReader(writer, Allocator.Temp);
+            var recvMsg = new DisconnectReasonMessage();
+            recvMsg.Deserialize(fbr, ref networkContext, msg.Version);
+
+            Assert.AreEqual("Foo", recvMsg.Reason);
+        }
+
+        [Test]
+        public void DisconnectReasonTooLong()
+        {
+            var networkContext = new NetworkContext();
+            var writer = new FastBufferWriter(20, Allocator.Temp, 20);
+            var msg = new DisconnectReasonMessage();
+            msg.Reason = "ThisStringIsWayLongerThanTwentyBytes";
+            msg.Serialize(writer, msg.Version);
+
+            var fbr = new FastBufferReader(writer, Allocator.Temp);
+            var recvMsg = new DisconnectReasonMessage();
+            recvMsg.Deserialize(fbr, ref networkContext, msg.Version);
+
+            Assert.IsEmpty(recvMsg.Reason);
+        }
+    }
+}

Tests/Editor/DisconnectMessageTests.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 55a1355c62fe14a118253f8bbee7c3cf
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Tests/Editor/InterpolatorTests.cs

@@ -105,6 +105,7 @@ namespace Unity.Netcode.EditorTests
             Assert.That(interpolator.GetInterpolatedValue(), Is.EqualTo(2f).Within(k_Precision));
         }
 
+        [Ignore("TODO: Fix this test to still handle testing message loss without extrapolation")]
         [Test]
         public void MessageLoss()
         {
@@ -305,6 +306,7 @@ namespace Unity.Netcode.EditorTests
             Assert.Throws<InvalidOperationException>(() => interpolator.Update(1f, serverTime));
         }
 
+        [Ignore("TODO: Fix this test to still test duplicated values without extrapolation")]
         [Test]
         public void TestDuplicatedValues()
         {

Tests/Editor/Messaging/MessageReceivingTests.cs

@@ -18,12 +18,12 @@ namespace Unity.Netcode.EditorTests
             public static bool Handled;
             public static List<TestMessage> DeserializedValues = new List<TestMessage>();
 
-            public void Serialize(FastBufferWriter writer)
+            public void Serialize(FastBufferWriter writer, int targetVersion)
             {
                 writer.WriteValueSafe(this);
             }
 
-            public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
             {
                 Deserialized = true;
                 reader.ReadValueSafe(out this);
@@ -35,6 +35,8 @@ namespace Unity.Netcode.EditorTests
                 Handled = true;
                 DeserializedValues.Add(this);
             }
+
+            public int Version => 0;
         }
 
         private class TestMessageProvider : IMessageProvider
@@ -46,7 +48,8 @@ namespace Unity.Netcode.EditorTests
                     new MessagingSystem.MessageWithHandler
                     {
                         MessageType = typeof(TestMessage),
-                        Handler = MessagingSystem.ReceiveMessage<TestMessage>
+                        Handler = MessagingSystem.ReceiveMessage<TestMessage>,
+                        GetVersion = MessagingSystem.CreateMessageAndGetVersion<TestMessage>
                     }
                 };
             }
@@ -62,6 +65,7 @@ namespace Unity.Netcode.EditorTests
             TestMessage.DeserializedValues.Clear();
 
             m_MessagingSystem = new MessagingSystem(new NopMessageSender(), this, new TestMessageProvider());
+            m_MessagingSystem.SetVersion(0, XXHash.Hash32(typeof(TestMessage).FullName), 0);
         }
 
         [TearDown]

Tests/Editor/Messaging/MessageRegistrationTests.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using NUnit.Framework;
 
@@ -11,12 +10,12 @@ namespace Unity.Netcode.EditorTests
             public int A;
             public int B;
             public int C;
-            public void Serialize(FastBufferWriter writer)
+            public void Serialize(FastBufferWriter writer, int targetVersion)
             {
                 writer.WriteValue(this);
             }
 
-            public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
             {
                 return true;
             }
@@ -24,6 +23,8 @@ namespace Unity.Netcode.EditorTests
             public void Handle(ref NetworkContext context)
             {
             }
+
+            public int Version => 0;
         }
 
         private struct TestMessageTwo : INetworkMessage, INetworkSerializeByMemcpy
@@ -31,12 +32,12 @@ namespace Unity.Netcode.EditorTests
             public int A;
             public int B;
             public int C;
-            public void Serialize(FastBufferWriter writer)
+            public void Serialize(FastBufferWriter writer, int targetVersion)
             {
                 writer.WriteValue(this);
             }
 
-            public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
             {
                 return true;
             }
@@ -44,6 +45,8 @@ namespace Unity.Netcode.EditorTests
             public void Handle(ref NetworkContext context)
             {
             }
+
+            public int Version => 0;
         }
         private class TestMessageProviderOne : IMessageProvider
         {
@@ -54,12 +57,14 @@ namespace Unity.Netcode.EditorTests
                     new MessagingSystem.MessageWithHandler
                     {
                         MessageType = typeof(TestMessageOne),
-                        Handler = MessagingSystem.ReceiveMessage<TestMessageOne>
+                        Handler = MessagingSystem.ReceiveMessage<TestMessageOne>,
+                        GetVersion = MessagingSystem.CreateMessageAndGetVersion<TestMessageOne>
                     },
                     new MessagingSystem.MessageWithHandler
                     {
                         MessageType = typeof(TestMessageTwo),
-                        Handler = MessagingSystem.ReceiveMessage<TestMessageTwo>
+                        Handler = MessagingSystem.ReceiveMessage<TestMessageTwo>,
+                        GetVersion = MessagingSystem.CreateMessageAndGetVersion<TestMessageTwo>
                     }
                 };
             }
@@ -70,12 +75,12 @@ namespace Unity.Netcode.EditorTests
             public int A;
             public int B;
             public int C;
-            public void Serialize(FastBufferWriter writer)
+            public void Serialize(FastBufferWriter writer, int targetVersion)
             {
                 writer.WriteValue(this);
             }
 
-            public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
             {
                 return true;
             }
@@ -83,6 +88,8 @@ namespace Unity.Netcode.EditorTests
             public void Handle(ref NetworkContext context)
             {
             }
+
+            public int Version => 0;
         }
         private class TestMessageProviderTwo : IMessageProvider
         {
@@ -93,7 +100,8 @@ namespace Unity.Netcode.EditorTests
                     new MessagingSystem.MessageWithHandler
                     {
                         MessageType = typeof(TestMessageThree),
-                        Handler = MessagingSystem.ReceiveMessage<TestMessageThree>
+                        Handler = MessagingSystem.ReceiveMessage<TestMessageThree>,
+                        GetVersion = MessagingSystem.CreateMessageAndGetVersion<TestMessageThree>
                     }
                 };
             }
@@ -103,12 +111,12 @@ namespace Unity.Netcode.EditorTests
             public int A;
             public int B;
             public int C;
-            public void Serialize(FastBufferWriter writer)
+            public void Serialize(FastBufferWriter writer, int targetVersion)
             {
                 writer.WriteValue(this);
             }
 
-            public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
             {
                 return true;
             }
@@ -116,6 +124,8 @@ namespace Unity.Netcode.EditorTests
             public void Handle(ref NetworkContext context)
             {
             }
+
+            public int Version => 0;
         }
         private class TestMessageProviderThree : IMessageProvider
         {
@@ -126,7 +136,8 @@ namespace Unity.Netcode.EditorTests
                     new MessagingSystem.MessageWithHandler
                     {
                         MessageType = typeof(TestMessageFour),
-                        Handler = MessagingSystem.ReceiveMessage<TestMessageFour>
+                        Handler = MessagingSystem.ReceiveMessage<TestMessageFour>,
+                        GetVersion = MessagingSystem.CreateMessageAndGetVersion<TestMessageFour>
                     }
                 };
             }
@@ -137,9 +148,9 @@ namespace Unity.Netcode.EditorTests
         {
             var sender = new NopMessageSender();
 
-            var systemOne = new MessagingSystem(sender, null, new TestMessageProviderOne());
-            var systemTwo = new MessagingSystem(sender, null, new TestMessageProviderTwo());
-            var systemThree = new MessagingSystem(sender, null, new TestMessageProviderThree());
+            using var systemOne = new MessagingSystem(sender, null, new TestMessageProviderOne());
+            using var systemTwo = new MessagingSystem(sender, null, new TestMessageProviderTwo());
+            using var systemThree = new MessagingSystem(sender, null, new TestMessageProviderThree());
 
             using (systemOne)
             using (systemTwo)
@@ -161,9 +172,9 @@ namespace Unity.Netcode.EditorTests
         {
             var sender = new NopMessageSender();
 
-            var systemOne = new MessagingSystem(sender, null, new TestMessageProviderOne());
-            var systemTwo = new MessagingSystem(sender, null, new TestMessageProviderTwo());
-            var systemThree = new MessagingSystem(sender, null, new TestMessageProviderThree());
+            using var systemOne = new MessagingSystem(sender, null, new TestMessageProviderOne());
+            using var systemTwo = new MessagingSystem(sender, null, new TestMessageProviderTwo());
+            using var systemThree = new MessagingSystem(sender, null, new TestMessageProviderThree());
 
             using (systemOne)
             using (systemTwo)
@@ -183,11 +194,11 @@ namespace Unity.Netcode.EditorTests
 
         internal class AAAEarlyLexicographicNetworkMessage : INetworkMessage
         {
-            public void Serialize(FastBufferWriter writer)
+            public void Serialize(FastBufferWriter writer, int targetVersion)
             {
             }
 
-            public bool Deserialize(FastBufferReader reader, ref NetworkContext context)
+            public bool Deserialize(FastBufferReader reader, ref NetworkContext context, int receivedMessageVersion)
             {
                 return true;
             }
@@ -195,6 +206,8 @@ namespace Unity.Netcode.EditorTests
             public void Handle(ref NetworkContext context)
             {
             }
+
+            public int Version => 0;
         }
 
 #pragma warning disable IDE1006
@@ -212,18 +225,19 @@ namespace Unity.Netcode.EditorTests
                 var messageWithHandler = new MessagingSystem.MessageWithHandler();
 
                 messageWithHandler.MessageType = typeof(zzzLateLexicographicNetworkMessage);
+                messageWithHandler.GetVersion = MessagingSystem.CreateMessageAndGetVersion<zzzLateLexicographicNetworkMessage>;
                 listMessages.Add(messageWithHandler);
 
                 messageWithHandler.MessageType = typeof(ConnectionRequestMessage);
+                messageWithHandler.GetVersion = MessagingSystem.CreateMessageAndGetVersion<ConnectionRequestMessage>;
                 listMessages.Add(messageWithHandler);
 
                 messageWithHandler.MessageType = typeof(ConnectionApprovedMessage);
-                listMessages.Add(messageWithHandler);
-
-                messageWithHandler.MessageType = typeof(OrderingMessage);
+                messageWithHandler.GetVersion = MessagingSystem.CreateMessageAndGetVersion<ConnectionApprovedMessage>;
                 listMessages.Add(messageWithHandler);
 
                 messageWithHandler.MessageType = typeof(AAAEarlyLexicographicNetworkMessage);
+                messageWithHandler.GetVersion = MessagingSystem.CreateMessageAndGetVersion<AAAEarlyLexicographicNetworkMessage>;
                 listMessages.Add(messageWithHandler);
 
                 return listMessages;
@@ -235,67 +249,18 @@ namespace Unity.Netcode.EditorTests
         {
             var sender = new NopMessageSender();
             var provider = new OrderingMessageProvider();
-            var messagingSystem = new MessagingSystem(sender, null, provider);
+            using var messagingSystem = new MessagingSystem(sender, null, provider);
 
-            // the 3 priority messages should appear first, in lexicographic order
+            // the 2 priority messages should appear first, in lexicographic order
             Assert.AreEqual(messagingSystem.MessageTypes[0], typeof(ConnectionApprovedMessage));
             Assert.AreEqual(messagingSystem.MessageTypes[1], typeof(ConnectionRequestMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[2], typeof(OrderingMessage));
 
             // the other should follow after
-            Assert.AreEqual(messagingSystem.MessageTypes[3], typeof(AAAEarlyLexicographicNetworkMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[4], typeof(zzzLateLexicographicNetworkMessage));
+            Assert.AreEqual(messagingSystem.MessageTypes[2], typeof(AAAEarlyLexicographicNetworkMessage));
+            Assert.AreEqual(messagingSystem.MessageTypes[3], typeof(zzzLateLexicographicNetworkMessage));
 
             // there should not be any extras
-            Assert.AreEqual(messagingSystem.MessageHandlerCount, 5);
-
-            // reorder the zzz one to position 3
-            messagingSystem.ReorderMessage(3, XXHash.Hash32(typeof(zzzLateLexicographicNetworkMessage).FullName));
-
-            // the 3 priority messages should still appear first, in lexicographic order
-            Assert.AreEqual(messagingSystem.MessageTypes[0], typeof(ConnectionApprovedMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[1], typeof(ConnectionRequestMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[2], typeof(OrderingMessage));
-
-            // the other should follow after, but reordered
-            Assert.AreEqual(messagingSystem.MessageTypes[3], typeof(zzzLateLexicographicNetworkMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[4], typeof(AAAEarlyLexicographicNetworkMessage));
-
-            // there should still not be any extras
-            Assert.AreEqual(messagingSystem.MessageHandlerCount, 5);
-
-            // verify we get an exception when asking for an invalid position
-            try
-            {
-                messagingSystem.ReorderMessage(-1, XXHash.Hash32(typeof(zzzLateLexicographicNetworkMessage).FullName));
-                Assert.Fail();
-            }
-            catch (ArgumentException)
-            {
-            }
-
-            // reorder the zzz one to position 3, again, to check nothing bad happens
-            messagingSystem.ReorderMessage(3, XXHash.Hash32(typeof(zzzLateLexicographicNetworkMessage).FullName));
-
-            // the two non-priority should not have moved
-            Assert.AreEqual(messagingSystem.MessageTypes[3], typeof(zzzLateLexicographicNetworkMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[4], typeof(AAAEarlyLexicographicNetworkMessage));
-
-            // there should still not be any extras
-            Assert.AreEqual(messagingSystem.MessageHandlerCount, 5);
-
-            // 4242 is a random hash that should not match anything
-            messagingSystem.ReorderMessage(3, 4242);
-
-            // that should result in an extra entry
-            Assert.AreEqual(messagingSystem.MessageHandlerCount, 6);
-
-            // with a null handler
-            Assert.AreEqual(messagingSystem.MessageHandlers[3], null);
-
-            // and it should have bumped the previous messages down
-            Assert.AreEqual(messagingSystem.MessageTypes[4], typeof(zzzLateLexicographicNetworkMessage));
-            Assert.AreEqual(messagingSystem.MessageTypes[5], typeof(AAAEarlyLexicographicNetworkMessage));
+            Assert.AreEqual(messagingSystem.MessageHandlerCount, 4);
         }
     }
 }