Bug Pipeline silently dropping messages when window gains focus.

Hi. I have a really simple setup using the ReliableSequencedPipelineStage (2.0.0-pre.2, Unity 2022.2.0b8) where messages are being dropped without any kind of console message (I am aware of the 32 limit but it is no showing up in console, I am not sure if it is the same problem).

The server code sends a uint for every frame and client prints an error for every number missing.

To reproduce:
- in two different unity editors add the "Menu" script to some game object and play
- in one editor click "Start server"
- in a second editor click "Start client"
- in the first editor click "Start simulation"
Server will start to send numers to the client, server and client will log those numbers.
- click the second editor
When second editor gains focus, after a mini halt, some messages will be skipped and the missing numbers will be logged as errors.

Code (CSharp):

1. using Unity.Networking.Transport;
2. using UnityEngine;
3.  
4. public class Menu : MonoBehaviour
5. {
6.     private Server server;
7.     private Client client;
8.  
9.     private bool serverRunning;
10.     private bool clientRunning;
11.  
12.     private void OnGUI()
13.     {
14.         if (!serverRunning && !clientRunning && GUILayout.Button("Start server"))
15.         {
16.             server = new Server();
17.             var endpoint = NetworkEndpoint.AnyIpv4;
18.             endpoint.Port = 9000;
19.             server.Initialize(endpoint);
20.             serverRunning = true;
21.         }
22.        
23.         if (!serverRunning && !clientRunning && GUILayout.Button("Start client"))
24.         {
25.             client = new Client();
26.             client.Initialize(NetworkEndpoint.Parse("127.0.0.1", 9000));
27.             clientRunning = true;
28.         }
29.  
30.         if (serverRunning && GUILayout.Button("Start simulation"))
31.         {
32.             server.sendTest = true;
33.         }
34.     }
35.    
36.     void Update()
37.     {
38.         if(serverRunning) server.Update();
39.         if(clientRunning) client.Update();
40.     }
41. }
42.  

Code (CSharp):

1. using System;
2. using Unity.Collections;
3. using Unity.Networking.Transport;
4. using UnityEngine;
5.  
6. public struct Server : IDisposable
7. {
8.     private NetworkDriver driver;
9.     private NetworkPipeline pipeline;
10.     private NativeList<NetworkConnection> connections;
11.        
12.     public bool sendTest;
13.     private uint acc;
14.  
15.     public void Initialize(NetworkEndpoint endpoint)
16.     {
17.         Debug.Log($"SERVER: Initializing at " + endpoint.ToString());
18.            
19.         var settings = new NetworkSettings();
20.         settings.WithNetworkConfigParameters(disconnectTimeoutMS: 3600000);
21.         driver = NetworkDriver.Create(settings);
22.         pipeline = driver.CreatePipeline(typeof(ReliableSequencedPipelineStage));
23.        
24.         if (driver.Bind(endpoint) != 0)
25.             Debug.Log($"SERVER: Failed to bind to port {endpoint.Port}");
26.         else
27.             driver.Listen();
28.  
29.         connections = new NativeList<NetworkConnection>(16, Allocator.Persistent);
30.     }
31.  
32.     public void Dispose()
33.     {
34.         driver.Dispose();
35.         connections.Dispose();
36.     }
37.  
38.     public void Update()
39.     {
40.         driver.ScheduleUpdate().Complete();
41.  
42.         // CleanUpConnections
43.         for (int i = connections.Length - 1; i >= 0; i--)
44.         {
45.             if (!connections[i].IsCreated)
46.             {
47.                 connections.RemoveAt(i);
48.             }
49.         }
50.  
51.         // AcceptNewConnections
52.         NetworkConnection newConnection;
53.         while ((newConnection = driver.Accept()) != default)
54.         {
55.             connections.Add(newConnection);
56.             Debug.Log($"SERVER: Accepted a connection: clientIndex = {connections.Length - 1}");
57.         }
58.  
59.         // Handle messages
60.         for (int clientIndex = 0; clientIndex < connections.Length; clientIndex++)
61.         {
62.             var connection = connections[clientIndex];
63.             NetworkEvent.Type cmd;
64.             while ((cmd = driver.PopEventForConnection(connection, out var reader)) != NetworkEvent.Type.Empty)
65.             {
66.                 if (cmd == NetworkEvent.Type.Data)
67.                 {
68.                        
69.                 }
70.                 else if (cmd == NetworkEvent.Type.Disconnect)
71.                 {
72.                     Debug.Log($"SERVER: Client disconnected from server: clientIndex = {clientIndex}");
73.                     connections[clientIndex] = default(NetworkConnection);
74.                 }
75.             }
76.         }
77.  
78.         if (sendTest)
79.         {
80.             acc++;
81.                
82.             Debug.Log($"Sending {acc}");
83.                
84.             for (int i = 0; i < connections.Length; i++)
85.             {
86.                 var connection = connections[i];
87.  
88.                 driver.BeginSend(pipeline, connection, out var writer);
89.                 writer.WriteUInt(acc);
90.                 driver.EndSend(writer);
91.             }
92.         }
93.     }
94. }

Code (CSharp):

1. using System;
2. using Unity.Networking.Transport;
3. using UnityEngine;
4.  
5. public struct Client : IDisposable
6. {
7.     public NetworkDriver driver;
8.     public NetworkPipeline pipeline;
9.     public NetworkConnection connection;
10.  
11.     public uint acc;
12.  
13.     public void Initialize(NetworkEndpoint endPoint)
14.     {
15.         Debug.Log($"CLIENT: Connecting to server in {endPoint.ToString()}");
16.  
17.         var settings = new NetworkSettings();
18.         settings.WithNetworkConfigParameters(disconnectTimeoutMS: 3600000);
19.         driver = NetworkDriver.Create(settings);
20.         pipeline = driver.CreatePipeline(typeof(ReliableSequencedPipelineStage));
21.         connection = driver.Connect(endPoint);
22.     }
23.  
24.     public void Dispose()
25.     {
26.         driver.Dispose();
27.     }
28.        
29.     public void Update()
30.     {
31.         driver.ScheduleUpdate().Complete();
32.  
33.         if (!connection.IsCreated)
34.         {
35.             Debug.Log("CLIENT: Connection failed");
36.             return;
37.         }
38.  
39.         var cmd = default(NetworkEvent.Type);
40.         while ((cmd = connection.PopEvent(driver, out var reader)) != default)
41.         {
42.             switch (cmd)
43.             {
44.                 case NetworkEvent.Type.Connect:
45.                 {
46.                     Debug.Log("CLIENT: Connected to server");
47.                     break;
48.                 }
49.                 case NetworkEvent.Type.Data:
50.                 {
51.                     var serverAcc = reader.ReadUInt();
52.  
53.                     while (serverAcc > acc + 1)
54.                     {
55.                         Debug.LogError($"Missing {++acc}");
56.                     }
57.  
58.                     Debug.Log($"Receiving {serverAcc}");
59.                     acc = serverAcc;
60.  
61.                     break;
62.                 }
63.                 case NetworkEvent.Type.Disconnect:
64.                 {
65.                     Debug.Log("CLIENT: Disconnected from server");
66.                     connection = default(NetworkConnection);
67.                     break;
68.                 }
69.                 default: throw new Exception();
70.             }
71.         }
72.     }
73. }