Event dispatch shouldn't fail when one of the clients disconnects

CoreRemoting.Tests/RpcTests.cs

@@ -1,7 +1,10 @@
 using System;
+using System.ComponentModel;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
+using CoreRemoting.Channels.Websocket;
+using CoreRemoting.DependencyInjection;
 using CoreRemoting.Serialization;
 using CoreRemoting.Tests.ExternalTypes;
 using CoreRemoting.Tests.Tools;
@@ -163,7 +166,7 @@ void ClientAction()
             clientThread.Start();
             clientThread.Join();
 
-            _serverFixture.Server.Config.MessageEncryption = true;
+            _serverFixture.Server.Config.MessageEncryption = false;
 
             Assert.True(_remoteServiceCalled);
             Assert.Equal(0, _serverFixture.ServerErrorCount);
@@ -509,5 +512,56 @@ public void NonSerializableError_method_throws_Exception()
                 _serverFixture.ServerErrorCount = 0;
             }
         }
+
+        [Fact]
+        public async Task Disposed_client_subscription_doesnt_break_other_clients()
+        {
+            async Task roundtrip(bool encryption)
+            {
+                var oldEncryption = _serverFixture.Server.Config.MessageEncryption;
+                _serverFixture.Server.Config.MessageEncryption = encryption;
+
+                try
+                {
+                    RemotingClient createClient() => new RemotingClient(new ClientConfig()
+                    {
+                        ServerPort = _serverFixture.Server.Config.NetworkPort,
+                        MessageEncryption = encryption,
+                    });
+
+                    using var client1 = createClient();
+                    using var client2 = createClient();
+
+                    client1.Connect();
+                    client2.Connect();
+
+                    var proxy1 = client1.CreateProxy<ITestService>();
+                    var fired1 = new TaskCompletionSource<bool>();
+                    proxy1.ServiceEvent += () => fired1.TrySetResult(true);
+
+                    var proxy2 = client2.CreateProxy<ITestService>();
+                    var fired2 = new TaskCompletionSource<bool>();
+                    proxy2.ServiceEvent += () => fired2.TrySetResult(true);
+
+                    // early disposal, proxy1 subscription isn't canceled
+                    client1.Disconnect();
+
+                    proxy2.FireServiceEvent();
+                    Assert.True(await fired2.Task);
+                    Assert.True(fired2.Task.IsCompleted);
+                    Assert.False(fired1.Task.IsCompleted);
+                }
+                finally
+                {
+                    _serverFixture.Server.Config.MessageEncryption = oldEncryption;
+                }
+            }
+
+            // works!
+            await roundtrip(encryption: false);
+
+            // fails!
+            await roundtrip(encryption: true);
+        }
     }
 }

CoreRemoting.Tests/ServerFixture.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using CoreRemoting.DependencyInjection;
 using CoreRemoting.Tests.Tools;
 using Xunit;
@@ -65,7 +66,10 @@ public ServerFixture()
     public void Dispose()
     {
         if (Server != null)
+        {
+            Thread.Sleep(100); // work around WatsonTcp 6.0.2 bug
             Server.Dispose();
+        }
     }
 }
 

CoreRemoting/RemotingSession.cs

@@ -42,7 +42,7 @@ public sealed class RemotingSession : IDisposable
         /// Event: Fired before the session is disposed to do some clean up.
         /// </summary>
         public event Action BeforeDispose;
-        
+
         #endregion
 
         #region Construction
@@ -70,7 +70,7 @@ internal RemotingSession(int keySize, byte[] clientPublicKey, IRemotingServer se
             _delegateProxyCache = new ConcurrentDictionary<Guid, IDelegateProxy>();
             _rawMessageTransport = rawMessageTransport ?? throw new ArgumentNullException(nameof(rawMessageTransport));
             _clientPublicKeyBlob = clientPublicKey;
-            
+
             _rawMessageTransport.ReceiveMessage += OnReceiveMessage;
             _rawMessageTransport.ErrorOccured += OnErrorOccured;
 
@@ -122,6 +122,10 @@ internal RemotingSession(int keySize, byte[] clientPublicKey, IRemotingServer se
             _remoteDelegateInvocationEventAggregator.RemoteDelegateInvocationNeeded +=
                 (_, uniqueCallKey, handlerKey, arguments) =>
                 {
+                    // handle graceful client disconnection
+                    if (_isDisposing)
+                        return null;
+
                     var sharedSecret =
                         MessageEncryption
                             ? _sessionId.ToByteArray()
@@ -134,7 +138,7 @@ internal RemotingSession(int keySize, byte[] clientPublicKey, IRemotingServer se
                             HandlerKey = handlerKey,
                             DelegateArguments = arguments
                         };
-                    
+
                     var remoteDelegateInvocationWebsocketMessage =
                         _server.MessageEncryptionManager
                             .CreateWireMessage(
@@ -144,9 +148,19 @@ internal RemotingSession(int keySize, byte[] clientPublicKey, IRemotingServer se
                                 keyPair: _keyPair,
                                 messageType: "invoke");
 
-                    // Invoke remote delegate on client
-                    _rawMessageTransport?.SendMessage(
-                        _server.Serializer.Serialize(remoteDelegateInvocationWebsocketMessage));
+                    try
+                    {
+                        // Invoke remote delegate on client
+                        _rawMessageTransport?.SendMessage(
+                            _server.Serializer.Serialize(remoteDelegateInvocationWebsocketMessage));
+                    }
+                    catch (Exception ex)
+                    {
+                        // handle unexpected client disconnection
+                        OnErrorOccured("Failed to dispatch the remote event. " +
+                            $"Session: {SessionId}, Unique call key: {uniqueCallKey}, " +
+                            $"Handler key: {handlerKey}", ex);
+                    }
 
                     return null;
                 };
@@ -162,7 +176,7 @@ internal RemotingSession(int keySize, byte[] clientPublicKey, IRemotingServer se
         private void OnErrorOccured(string errorMessage, Exception ex)
         {
             var exception = new RemotingException(errorMessage, innerEx: ex); 
-            
+
             ((RemotingServer)_server).OnError(exception);
         }
 
@@ -705,7 +719,7 @@ private bool MapLinqExpressionArgument(Type argumentType, object argument, out o
 
             return true;
         }
-        
+
         #endregion
 
         #region Close session