| AddPlayer | Internal networking system message for adding player objects to client instances. |
| Animation | Internal networking system message for sending synchronizing animation state. |
| AnimationParameters | Internal networking system message for sending synchronizing animation parameter state. |
| AnimationTrigger | Internal networking system message for sending animation triggers. |
| Command | Internal networking system message for sending a command from client to server. |
| Connect | Internal networking system message for communicating a connection has occurred. |
| CRC | Internal networking system message for HLAPI CRC checking. |
| Disconnect | Internal networking system message for communicating a disconnect has occurred,. |
| Error | Internal networking system message for communicating an error. |
| Fragment | Internal networking system message for identifying fragmented packets. |
| Highest | The highest value of built-in networking system message ids. User messages must be above this value. |
| InternalHighest | The highest value of internal networking system message ids. User messages must be above this value. User code cannot replace these handlers. |
| LobbyAddPlayerFailed | Internal networking system message for communicating failing to add lobby player. |
| LobbyReadyToBegin | Internal networking system message for communicating a player is ready in the lobby. |
| LobbyReturnToLobby | Internal networking system messages used to return the game to the lobby scene. |
| LobbySceneLoaded | Internal networking system message for communicating a lobby player has loaded the game scene. |
| LocalChildTransform | Internal networking system message for sending tranforms for client object from client to server. |
| LocalClientAuthority | Internal networking system message for setting authority to a client for an object. |
| LocalPlayerTransform | Internal networking system message for sending tranforms from client to server. |
| NetworkInfo | Internal networking system message for sending information about network peers to clients. |
| NotReady | Internal networking system message for server to tell clients they are no longer ready. |
| ObjectDestroy | Internal networking system message for destroying objects. |
| ObjectHide | Internal networking system message for hiding objects. |
| ObjectSpawn | Internal networking system message for spawning objects. |
| ObjectSpawnScene | Internal networking system message for spawning scene objects. |
| Owner | Internal networking system message for telling clients they own a player object. |
| PeerClientAuthority | Internal networking system message for sending information about changes in authority for non-player objects to clients. |
| Ready | Internal networking system message for clients to tell server they are ready. |
| ReconnectPlayer | Internal networking system message used when a client connects to the new host of a game. |
| RemovePlayer | Internal networking system message for removing a player object which was spawned for a client. |
| Rpc | Internal networking system message for sending a ClientRPC from server to client. |
| Scene | Internal networking system message that tells clients which scene to load when they connect to a server. |
| SpawnFinished | Internal networking system messages used to tell when the initial contents of a scene is being spawned. |
| SyncEvent | Internal networking system message for sending a SyncEvent from server to client. |
| SyncList | Internal networking system message for sending a USyncList generic list. |
| UpdateVars | Internal networking system message for updating SyncVars on a client from a server. |