Fix web sockets closing ungracefully

Emby.Dlna/PlayTo/PlayToController.cs

@@ -889,6 +889,11 @@ namespace Emby.Dlna.PlayTo
             return Task.CompletedTask;
         }
 
+        public void CloseAllWebSockets(CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException();
+        }
+
         private class StreamParams
         {
             private MediaSourceInfo _mediaSource;

Emby.Server.Implementations/HttpServer/WebSocketConnection.cs

@@ -231,6 +231,15 @@ namespace Emby.Server.Implementations.HttpServer
                 CancellationToken.None);
         }
 
+        /// <summary>
+        /// Gracefully closes the socket.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        public void CloseSocket(CancellationToken cancellationToken)
+        {
+            _socket.CloseOutputAsync(WebSocketCloseStatus.NormalClosure, "System Shutdown", cancellationToken);
+        }
+
         /// <inheritdoc />
         public void Dispose()
         {

Emby.Server.Implementations/Session/SessionManager.cs

@@ -1363,9 +1363,26 @@ namespace Emby.Server.Implementations.Session
         {
             CheckDisposed();
 
+            CloseAllWebSockets(cancellationToken);
+
             return SendMessageToSessions(Sessions, SessionMessageType.ServerShuttingDown, string.Empty, cancellationToken);
         }
 
+        /// <summary>
+        /// Gracefully closes all web sockets in all sessions.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        private void CloseAllWebSockets(CancellationToken cancellationToken)
+        {
+            foreach (var session in Sessions)
+            {
+                foreach (var sessionController in session.SessionControllers)
+                {
+                    sessionController.CloseAllWebSockets(cancellationToken);
+                }
+            }
+        }
+
         /// <summary>
         /// Sends the server restart notification.
         /// </summary>

Emby.Server.Implementations/Session/WebSocketController.cs

@@ -88,6 +88,18 @@ namespace Emby.Server.Implementations.Session
                 cancellationToken);
         }
 
+        /// <summary>
+        /// Gracefully closes all web sockets.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        public void CloseAllWebSockets(CancellationToken cancellationToken)
+        {
+            foreach (var socket in _sockets)
+            {
+                socket.CloseSocket(cancellationToken);
+            }
+        }
+
         /// <inheritdoc />
         public void Dispose()
         {

MediaBrowser.Controller/Net/IWebSocketConnection.cs

@@ -58,5 +58,11 @@ namespace MediaBrowser.Controller.Net
         Task SendAsync<T>(WebSocketMessage<T> message, CancellationToken cancellationToken);
 
         Task ProcessAsync(CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Gracefully closes the socket.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        void CloseSocket(CancellationToken cancellationToken);
     }
 }

MediaBrowser.Controller/Session/ISessionController.cs

@@ -33,5 +33,11 @@ namespace MediaBrowser.Controller.Session
         /// <param name="cancellationToken">CancellationToken for operation.</param>
         /// <returns>A task.</returns>
         Task SendMessage<T>(SessionMessageType name, Guid messageId, T data, CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Gracefully closes all web sockets.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        void CloseAllWebSockets(CancellationToken cancellationToken);
     }
 }