Photon exception on client after disconnect event

[dwoodruffsf]

Describe the bug
After getting disconnected from photon, the client sometimes develops an exception that fires every frame. This bug is a complement to bug Unity-Technologies/com.unity.netcode.gameobjects#823. It isn't wrong that the client gets disconnected (although the timeout of only a few seconds is pretty aggressive). But it seems that the PhotonRealtimeTransport is in a bad state after the shutdown, and generates exceptions.

To Reproduce

1. Open the BossRoom demo in editor. Window->Photon Realtime->Highlight Server Settings.
2. Put in your own personal appid from photonengine.com
3. Start the game in a separate built client, select "Start", and then "Relay Host".
4. Start the game in editor, select "Join", "Relay Host", and the room name.
5. Once both host and client are in character select, pick character and enter the game.
6. Walk around with the joiner client and pick a fight with an imp (I think having some active network traffic is helpful in getting the exception).
7. Pull your network cable. Count to 5, then plug it back in.
8. Observe that sometimes (around 50% of the time), after you are returned to main menu, you get a continuous stream of exceptions from the PhotonRealtimeTransport

Actual outcome
An exception gets thrown every frame after a client gets disconnected from the Photon Relay Server.

Expected outcome
No exceptions are generated.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: [e.g. Windows 10]
• Unity Version: [e.g. 2019.1]
• MLAPI Version: [e.g. v6.0.1]
• MLAPI Commit: [e.g. https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/commit/c102935df1d7e0928283b48948fe96e5d96dd961]

Additional context

callstack of the Exception. m_Client is null, which is no surprise, since NetworkManager has already been Shutdown by this point.

Int32 MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:get_CurrentMasterId ()+0x0 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350ae57\Runtime\PhotonRealtimeTransport.Matchmaking.cs:[15:34-15:115]	C#
Int32 MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:GetPhotonRealtimeId (UInt64)+0xc at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350ae57\Runtime\PhotonRealtimeTransport.cs:[472:17-472:40]	C#
Void MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:RaisePhotonEvent (UInt64, Boolean, ArraySegment`1, Byte)+0xf at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350ae57\Runtime\PhotonRealtimeTransport.cs:[245:13-245:87]	C#
Void MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:FlushAllSendQueues ()+0x58 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350ae57\Runtime\PhotonRealtimeTransport.cs:[231:17-231:113]	C#

Void MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:LateUpdate ()+0x2 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350a\Runtime\PhotonRealtimeTransport.cs:[114:13-114:34] C#

This is the callstack showing the network shutdown the client gets, triggered by a Disconnect event from the Photon relay server.

Void MLAPI.NetworkManager:Shutdown ()+0x1 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.unity.multiplayer.mlapi@3e3aef6aa0\Runtime\Core\NetworkManager.cs:[603:13-603:66]	C#
Void MLAPI.NetworkManager:StopClient ()+0x3d at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.unity.multiplayer.mlapi@3e3aef6aa0\Runtime\Core\NetworkManager.cs:[512:13-512:24]	C#
Void MLAPI.NetworkManager:HandleRawTransportPoll (NetworkEvent, UInt64, NetworkChannel, ArraySegment`1, Single)+0x182 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.unity.multiplayer.mlapi@3e3aef6aa0\Runtime\Core\NetworkManager.cs:[895:25-895:38]	C#
Void MLAPI.Transports.NetworkTransport:InvokeOnTransportEvent (NetworkEvent, UInt64, NetworkChannel, ArraySegment`1, Single)+0x14 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.unity.multiplayer.mlapi@3e3aef6aa0\Runtime\Transports\NetworkTransport.cs:[123:13-123:92]	C#

Void MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:InvokeTransportEvent (NetworkEvent, UInt64, NetworkChannel, ArraySegment`1)+0x41 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350a\Runtime\PhotonRealtimeTransport.cs:[424:21-424:113] C#
Void MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:OnPlayerLeftRoom (Player)+0x3c at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350a\Runtime\PhotonRealtimeTransport.Room.cs:[48:17-48:58] C#
Void Photon.Realtime.InRoomCallbacksContainer:OnPlayerLeftRoom (Player)+0x22 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350a\Runtime\Photon\PhotonRealtime\Code\LoadBalancingClient.cs:[4184:17-4184:54] C#
Void Photon.Realtime.LoadBalancingClient:OnEvent (EventData)+0x2d5 at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350a\Runtime\Photon\PhotonRealtime\Code\LoadBalancingClient.cs:[3197:21-3197:84] C#
Boolean ExitGames.Client.Photon.PeerBase:DeserializeMessageAndCallback (StreamBuffer)+0x2e9 at :-1 C#
Boolean ExitGames.Client.Photon.EnetPeer:DispatchIncomingCommands ()+0x3b6 at :-1 C#
Boolean ExitGames.Client.Photon.PhotonPeer:DispatchIncomingCommands ()+0x3a at :-1 C#
Void MLAPI.Transports.PhotonRealtime.PhotonRealtimeTransport:Update ()+0x1c at C:\dev\com.unity.multiplayer.samples.coop\Library\PackageCache\com.mlapi.contrib.transport.photon-realtime@3f0350a\Runtime\PhotonRealtimeTransport.cs:[105:24-105:86] C#

[Tobias-EG]

Thanks for the report. Easy to repro. Fix is in a pr. Same core issue as #69 .

[LukeStampfli]

Fixed by #73