Close sessions for lost WebSockets to prevent zombie SyncPlay groups (#17079)

Close sessions for lost WebSockets to prevent zombie SyncPlay groups

Emby.Server.Implementations/HttpServer/WebSocketConnection.cs

@@ -127,8 +127,12 @@ namespace Emby.Server.Implementations.HttpServer
                 {
                     receiveResult = await _socket.ReceiveAsync(memory, cancellationToken).ConfigureAwait(false);
                 }
-                catch (WebSocketException ex)
+                catch (Exception ex) when (ex is WebSocketException or ObjectDisposedException or OperationCanceledException)
                 {
+                    // ObjectDisposedException/OperationCanceledException: the socket was torn
+                    // down underneath us (e.g. by the keep-alive watchdog after the connection
+                    // was declared lost). Fall through so Closed is still raised and the
+                    // session can release this connection.
                     _logger.LogWarning("WS {IP} error receiving data: {Message}", RemoteEndPoint, ex.Message);
                     break;
                 }

Emby.Server.Implementations/Session/SessionWebSocketListener.cs

@@ -246,8 +246,21 @@ namespace Emby.Server.Implementations.Session
                     _logger.LogInformation("Lost {0} WebSockets.", lost.Count);
                     foreach (var webSocket in lost)
                     {
-                        // TODO: handle session relative to the lost webSocket
                         RemoveWebSocket(webSocket);
+
+                        // The connection stopped answering keep-alives, so a close frame will
+                        // never arrive and the pending receive loop would hang forever, keeping
+                        // the session (and e.g. its SyncPlay group membership) alive. Disposing
+                        // the connection aborts the receive loop, which raises Closed and lets
+                        // the session end normally.
+                        try
+                        {
+                            webSocket.Dispose();
+                        }
+                        catch (Exception exception)
+                        {
+                            _logger.LogWarning(exception, "Error disposing lost WebSocket from {RemoteEndPoint}.", webSocket.RemoteEndPoint);
+                        }
                     }
                 }
             }