public static AppFunc Middleware(AppFunc app) { return env => { var request = new OwinRequest(env); var websocketVersion = request.Get<string>(OwinConstants.WebSocket.Version); WebSocketAccept webSocketAccept = request.Get<WebSocketAccept>(OwinConstants.WebSocket.Accept); if (request.CanUpgrade && websocketVersion == null) // If we have opaque support and no WebSocket support yet { if (IsWebSocketRequest(env)) { // TODO: check for correct requested version of WebSocket protocol IDictionary<string, object> acceptOptions = null; WebSocketFunc webSocketFunc = null; // Announce websocket support env[OwinConstants.WebSocket.Accept] = new WebSocketAccept( (options, callback) => { acceptOptions = options; webSocketFunc = callback; env[OwinConstants.ResponseStatusCode] = 101; }); return app(env).ContinueWith(t => { OwinResponse response = new OwinResponse(env); if (response.StatusCode == 101 && webSocketFunc != null) { SetWebSocketResponseHeaders(env, acceptOptions); request.UpgradeDelegate(acceptOptions, opaqueEnv => { WebSocketLayer webSocket = new WebSocketLayer(opaqueEnv); return webSocketFunc(webSocket.Environment) .ContinueWith(tt => webSocket.CleanupAsync()); }); } }); } } // else return app(env); }; }