fix: Clear adapter send queues on client disconnection

com.unity.netcode.adapter.utp/CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to this package will be documented in this file. The format
 
 ### Fixed
 
+- Fixed issue where disconnecting from the server with data still in the queue would result in an error message about a stale connection. (#1649)
 - Fixed issue where the server `NetworkEndPoint` would fail to be created when 'Server Listen Address' is empty. (#1636)
 - Fixed issue with native collections not all being disposed of when destroying the component without shutting it down properly. This would result in errors in the console and memory leaks. (#1640)
 - Fixed an issue where packets causing errors would not be removed from the send queue, which would cause the error message to be spammed on every frame as the adapter would try to resend the packet. (#1648)

com.unity.netcode.adapter.utp/Tests/Runtime/ConnectionTests.cs

@@ -1,4 +1,5 @@
 using NUnit.Framework;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
@@ -23,15 +24,15 @@ public IEnumerator Cleanup()
             if (m_Server)
             {
                 m_Server.Shutdown();
-                Object.DestroyImmediate(m_Server);
+                UnityEngine.Object.DestroyImmediate(m_Server);
             }
 
             foreach (var transport in m_Clients)
             {
                 if (transport)
                 {
                     transport.Shutdown();
-                    Object.DestroyImmediate(transport);
+                    UnityEngine.Object.DestroyImmediate(transport);
                 }
             }
 
@@ -283,6 +284,46 @@ public IEnumerator DifferentServerAndListenAddresses()
             yield return null;
         }
 
+        // Check server disconnection with data in send queue.
+        [UnityTest]
+        public IEnumerator ServerDisconnectWithDataInQueue()
+        {
+            InitializeTransport(out m_Server, out m_ServerEvents);
+            InitializeTransport(out m_Clients[0], out m_ClientsEvents[0]);
+
+            m_Server.StartServer();
+            m_Clients[0].StartClient();
+
+            yield return WaitForNetworkEvent(NetworkEvent.Connect, m_ServerEvents);
+
+            var data = new ArraySegment<byte>(new byte[] { 42 });
+            m_Server.Send(m_ServerEvents[0].ClientID, data, NetworkDelivery.Unreliable);
+
+            m_Server.DisconnectRemoteClient(m_ServerEvents[0].ClientID);
+
+            yield return WaitForNetworkEvent(NetworkEvent.Disconnect, m_ClientsEvents[0]);
+        }
+
+        // Check client disconnection with data in send queue.
+        [UnityTest]
+        public IEnumerator ClientDisconnectWithDataInQueue()
+        {
+            InitializeTransport(out m_Server, out m_ServerEvents);
+            InitializeTransport(out m_Clients[0], out m_ClientsEvents[0]);
+
+            m_Server.StartServer();
+            m_Clients[0].StartClient();
+
+            yield return WaitForNetworkEvent(NetworkEvent.Connect, m_ServerEvents);
+
+            var data = new ArraySegment<byte>(new byte[] { 42 });
+            m_Clients[0].Send(m_Clients[0].ServerClientId, data, NetworkDelivery.Unreliable);
+
+            m_Clients[0].DisconnectLocalClient();
+
+            yield return WaitForNetworkEvent(NetworkEvent.Disconnect, m_ServerEvents);
+        }
+
         // Check that a server can disconnect a client after another client has disconnected.
         [UnityTest]
         public IEnumerator ServerDisconnectAfterClientDisconnect()