NetworkClient.OnCrc NullReferenceException issue

Scripting
1

I’ve been playing with Unity Networking, trying to have a prefab created when a client connects and also to create another separate object which contains the player data, (yes I could put them into one GameObject but I am trying to have them separate for now).

I have a NetworkManager object containing code along the lines of the following:

public class MyNetManager : NetworkManager
{
    public static NetworkHash128 PlayerInfoAssetId =
        NetworkHash128.Parse("79797901");
       
    [SerializeField]
    private GameObject _LobbyPlayerPrefab = null;

    protected void Awake()
    {
        // Register handler to spawn linked player info object
        ClientScene.RegisterSpawnHandler(MyNetManager.PlayerInfoAssetId,
            PlayerSpawnHandler, PlayerUnSpawnHandler);

        // Register the prefab we wish to use for the player in the lobby
        ClientScene.RegisterPrefab(_LobbyPlayerPrefab);
    }

    private GameObject PlayerSpawnHandler(
        Vector3 position, NetworkHash128 assetID)
    {
        return ServerClass.LocalInstance.AddLocalPlayer();
    }

    private void PlayerUnSpawnHandler(GameObject gameObject)
    {
        ServerClass.LocalInstance.RemoveLocalPlayer(gameObject);
    }

    public override void OnServerAddPlayer(NetworkConnection conn, short playerControllerId)
    {
        GameObject playerGameObj = ServerClass.SvrAddPlayer();
        PlayerClass pi = playerGameObj.GetComponent<PlayerClass>();

        GameObject panel = (GameObject)GameObject.Instantiate(
            _LobbyPlayerPrefab, Vector3.zero, Quaternion.identity);
        panel.name = string.Format("Player-Lobby-Panel-{0:00}", pi.PlayerId);

        NetworkServer.AddPlayerForConnection(conn, playerGameObj,
            playerControllerId, IbuNetManager.PlayerInfoAssetId);
    }
}

And another class along the lines of:

public class ServerClass : MonoBehaviour
{
    internal GameObject AddLocalPlayer()
    {
        GameObject playerGameObj = new GameObject("Player-???", typeof(PlayerClass));
        playerGameObj.transform.SetParent(this.transform);
        playerGameObj.transform.position = new Vector3();

        return playerGameObj;
    }
   
    internal void RemoveLocalPlayer(GameObject obj)
    {
        UnityEngine.Object.Destroy(obj);
    }
   
    public static GameObject SvrAddPlayer()
    {
        var svr = LocalInstance;

        // Create the master version of the player object
        var p = svr.AddLocalPlayer();
        PlayerClass pi = p.GetComponent<PlayerClass>();

        // Set our synced variables as we are on the server
        pi.SvrSetPlayerId(svr._NextPlayerId++);

        return p;
    }
}

When a client connects I have it successfully creating the prefab object, and sucessfully spawning off the seperate player game object. Everything appears to work correctly for the clients and server/host programs, except I keep getting the following error when a separate client is connecting to the server, (note not on the server/host connecting to itself):

NullReferenceException: Object reference not set to an instance of an object
UnityEngine.Networking.NetworkClient.OnCRC (UnityEngine.Networking.NetworkMessage netMsg) (at C:/buildslave/unity/build/Extensions/Networking/Runtime/NetworkClient.cs:626)
UnityEngine.Networking.NetworkConnection.HandleMessage (System.Collections.Generic.Dictionary`2 handler, UnityEngine.Networking.NetworkReader reader, Int32 receivedSize, Int32 channelId) (at C:/buildslave/unity/build/Extensions/Networking/Runtime/NetworkConnection.cs:302)
UnityEngine.Networking.NetworkClient.Update () (at C:/buildslave/unity/build/Extensions/Networking/Runtime/NetworkClient.cs:472)
UnityEngine.Networking.NetworkClient.UpdateClients () (at C:/buildslave/unity/build/Extensions/Networking/Runtime/NetworkClient.cs:686)
UnityEngine.Networking.NetworkIdentity.UNetStaticUpdate () (at C:/buildslave/unity/build/Extensions/Networking/Runtime/NetworkIdentity.cs:725)

After scratching my head a lot, I did find one method to stop this error from occurring… I added a new Prefab to the project containing a single component (the player class spawned by the AddLocalPlayer method), I then added this prefab to the Network manager registered spawnable prefabs.

So adding a prefab I never use, but containing a component that I spawn within a Spawn Handler function appears to have stopped this error from being thrown within the Unity code… This feels wrong to me as I don’t like having the additional prefab created which is never used anywhere and everything appears to work correctly except for the Null Reference exception error messages!

Is there a better way to stop getting this NullReferenceException? Is it a bug in Unity? Or am I just meant to have the unused prefab registered with the Network Manager?

2

I’m getting the same error but only on mobile. In PC and Mac builds it’s fine. Did you find a solution?

3

The only way I’ve been able to stop the error is by adding the script to an unused prefab. I’ve not found any other way of stopping the error sadly.