NetworkObject binding failed on Host and Client

[Pourfex]

Describe the bug
Main error : Cannot find pending soft sync object. Is the projects the same?
When starting an host that switch scene, the binding between any new client for any networkedobjects is not working. That result with different network id for scene objects (one that have networkedobject on).

To Reproduce
Steps to reproduce the behavior:
Go to this github repository : https://github.com/Pourfex/IssueSceneHostMlapi
Make 2 projects with this repository.
One should start playmode and press space to be the host.
One should start playmode and press b to be a client.

An error on client occured, you can check on the interaction scene the network id that are not the same.

The workaround for now is on the same repository on the branch "workaround"

https://github.com/Pourfex/IssueSceneHostMlapi/tree/workaround which is using Unity Scene loader before starting the host.

Expected behavior
The networked behaviour should have the same networking id and no error should be displayed

Screenshots
Error on client :

Environment (please complete the following information):

• OS: Windows 10
• Unity Version: 2019.3.3f1
• MLAPI Version: 6.0.1

Additional context
Use in another context, find the bug and discuss it with NFMynster on discord. The workaround is to use the Unity Scene loader before starting the host like this :

SceneManager.LoadScene("InteractionScene");
SceneManager.sceneLoaded += (arg0, arg1) => {
            NetworkingManager.Singleton.StartHost();
        };  

[TwoTenPvP]

I don't quite understand.

The to become server instance has Scene A loaded. Calls StartHost, then calls NetworkSceneManager to switch to Scene B. Then a client connects and you get that error?

[AhmetDmr02]

im getting this error either,but when i build the game to standalone im not getting this error i mean if you host from standalone build and connect from editor you will get this error but when you host from standalone and join from standalone there is gonna be no error

[dillonarnold]

I've also been seeing the exact same issue where hosting from a standalone leads to this error on the editor, but hosting on the editor or standalone -> standalone doesn't.

[NoelStephensUnity]

This is most likely due to the bug with the NetworkScenePostProcess class executing when a scene is loaded while in the editor.
The develop branch has a fix for this bug.
If you are adventurous and want to see if this fix will solve your issue, you could apply the following change the NetworkScenePostProcess locally:

public class NetworkScenePostProcess : MonoBehaviour
{
    [PostProcessScene(int.MaxValue)]
    public static void ProcessScene()
    {
        //If we are in playmode (editor or stand alone) we do not want this to execute
        if(Application.isPlaying)
        {
            return;
        }

Otherwise, you can wait for the next MLAPI release where this fix will be applied.

If you are adventurous and apply the above changes, please do let me know if this fixes the issues you are experiencing. If not, then I might need more information.

[dizzy2003]

That fix didnt work for me (I just have 1 scene loaded all the time),
it left all the in scene prefabs with NetworkInstanceID=0

Which then causes an exception

ArgumentException: An item with the same key has already been added. Key: 0
System.Collections.Generic.Dictionary2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) (at <695d1cc93cca45069c528c15c9fdd749>:0) System.Collections.Generic.Dictionary2[TKey,TValue].Add (TKey key, TValue value) (at <695d1cc93cca45069c528c15c9fdd749>:0)
MLAPI.Spawning.SpawnManager.ClientCollectSoftSyncSceneObjectSweep (MLAPI.NetworkedObject[] networkedObjects) (at Assets/MLAPI_source/MLAPI/Spawning/SpawnManager.cs:603)
MLAPI.Messaging.InternalMessageHandler.g__DelayedSpawnAction|4_0 (System.IO.Stream continuationStream) (at Assets/MLAPI_source/MLAPI/Messaging/InternalMessageHandler.cs:236)
MLAPI.Messaging.InternalMessageHandler.HandleConnectionApproved (System.UInt64 clientId, System.IO.Stream stream, System.Single receiveTime) (at Assets/MLAPI_source/MLAPI/Messaging/InternalMessageHandler.cs:352)
MLAPI.NetworkingManager.HandleIncomingData (System.UInt64 clientId, System.String channelName, System.ArraySegment1[T] data, System.Single receiveTime, System.Boolean allowBuffer) (at Assets/MLAPI_source/MLAPI/Core/NetworkingManager.cs:936) MLAPI.NetworkingManager.HandleRawTransportPoll (MLAPI.Transports.NetEventType eventType, System.UInt64 clientId, System.String channelName, System.ArraySegment1[T] payload, System.Single receiveTime) (at Assets/MLAPI_source/MLAPI/Core/NetworkingManager.cs:870)
MLAPI.NetworkingManager.Update () (at Assets/MLAPI_source/MLAPI/Core/NetworkingManager.cs:651)

[dizzy2003]

I assume the intention is to assign the NetworkID's offline in the editor, but for me in Unity 2021.1.0b8 its never calling NetworkScenePostProcess.ProcessScene at editor time, only when I hit play.

I tried restarting the editor, I tried loading a different scene then reloading the correct scene, no joy.

[NoelStephensUnity]

Hi dizzy2003,
I just had a chance to go back through some of the bugs assigned to me and follow up. This is indeed a bug and the fix is currently under review. Hopefully it will make it out for the first milestone release. The issue you are having I recently ran across some issues with scene loading and how it synchronizes objects.

If you feel adventurous: :)
This fix has many new updates in it that include name refactoring, so I would advise using a copy of an existing project or just use the new test project as a good starting point:
https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/tree/fix/softsynch
Additionally, there is a TestProject located in that branch(com.unity.multiplayer.mlapi\testproject):
That includes a scene transitioning and global game state management sample in it. You might find that useful as well.
When you load the TestProject, look for the "GlobalGameState" folder. Within that folder you will find a Scenes folder. Within the Scenes folder you will find an MLAPIBootStrap scene that includes the GlobalGameState component that allows you to dictate when scenes are loaded, when MLAPI needs to be instantiated, and it provides some additional examples of scene transitioning, in-game pausing, and other similar goodies. Since it is all "work in progress" we don't have any tutorials or documentation on proper usage, but feel free to respond here if you have further questions.

If you do feel adventurous and give that a shot, let me know how it works for you?
(please understand that this fix and the scene transitioning and global game state sample are "yet to be officially released")

[dizzy2003]

you changed every API!

you got rid of the invoke system (I liked) to use the automated system of Unet for RPC's :(

How do I send a rpc to every client except a specific one?

[dizzy2003]

any idea how to fix

Assets\MLAPI_source\Transport\Runtime\UTPTransport.cs(154,29): error CS0246: The type or namespace name 'Transport' could not be found (are you missing a using directive or an assembly reference?)
and 12 other related errors

I have made sure the uniy transport package 0.4.1 is in the project and that the UTPtransport asmdef has the unity 0.4.1 transport as a dependency

Have also tried newer transport packages

[dizzy2003]

TestProject fails to compile with.

Assets\GlobalGameState\Scripts\MenuControl.cs(16,13): error CS0246: The type or namespace name 'UnetTransport' could not be found (are you missing a using directive or an assembly reference?)

changing the type name to UNetTransport fixes it. (upper case N)