Something Breaks when spawning as Client

Unity Engine
,
23

The reason why this error happened to me is because there was some NetworkObject being spawned into the scene and I forgot to include it in my NetworkPrefabsList in my NetworkManager.

It’s really unhelpful that Unity throws the GlobalObjectIdHash in the error message, because this parameter is an internal field in the NetworkObject component, so its value cannot even be read by anyone other than Unity devs. That is, unless you use Reflection.

Here is a script I wrote to help me identify which prefab causes the error to be thrown. You can access it in Tools > Network Hash Finder. This is working in NGO v1.5.1, but might not work in future versions if the Unity devs move away from the GlobalObjectHashId solution. If a Unity dev reads this: please for the love of god make your tools easily accessible to your users so that we can debug your cryptic error messages without invoking Reflection black magic.

#if UNITY_EDITOR
using UnityEngine;
using UnityEditor;
using Unity.Netcode;
using System.Reflection;

public class NetworkHashFinder : EditorWindow
{
    private string hashInput;
    private NetworkObject output;

    [MenuItem("Tools/Network Hash Finder")]
    public static void InitializeWindow()
    {
        NetworkHashFinder window = GetWindow<NetworkHashFinder>();
        window.titleContent = new GUIContent("Network Hash Finder");
    }

    void OnGUI()
    {
        bool wasEnabled = GUI.enabled;

        EditorGUILayout.BeginHorizontal();
        {
            hashInput = EditorGUILayout.TextField("Hash ID", hashInput);
            GUI.enabled = VerifyIsInteger(hashInput);
            if (GUILayout.Button("Find"))
            {
                output = FindByHash(ParseInput(hashInput));
                if (output == null) Debug.Log("No GameObject found with hash ID '" + hashInput + "'");
            }
            GUI.enabled = wasEnabled;
        }
        EditorGUILayout.EndHorizontal();

        NetworkObject newOutput = EditorGUILayout.ObjectField("Object", output, typeof(NetworkObject), false) as NetworkObject;

        if (newOutput != output)
        {
            GUI.FocusControl(null);
            hashInput = newOutput.PrefabIdHash.ToString();
            output = newOutput;
        }

        if (GUILayout.Button("Clear"))
        {
            GUI.FocusControl(null);
            hashInput = "";
            output = null;
        }

        GUI.enabled = wasEnabled;
    }

    private uint ParseInput(string input)
    {
        return uint.Parse(input);
    }

    /// <summary>
    /// Use the hashID to find the GameObject that corresponds with it
    /// </summary>
    private NetworkObject FindByHash(uint hashID)
    {
        FieldInfo info = typeof(NetworkObject).GetField("GlobalObjectIdHash", BindingFlags.Instance | BindingFlags.NonPublic);
        if (info == null)
        {
            Debug.LogError("GlobalObjectIdHash field is null. Unity might have updated Netcode not to use this parameter anymore, in which case this tool is useless");
            return null;
        }
        foreach (NetworkObject obj in Resources.FindObjectsOfTypeAll<NetworkObject>())
        {
            uint GlobalObjectIdHash = (uint)info.GetValue(obj);
            if (GlobalObjectIdHash == hashID)
            {
                return obj;
            }
        }

        return null;
    }

    private bool VerifyIsInteger(string input)
    {
        try
        {
            uint.Parse(input);
            return true;
        }
        catch (System.Exception)
        {
            return false;
        }
    }
}
#endif
2 Likes