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POWebSocket Connection Drops before onmessage
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  1. POWebSocket Connection Drops before onmessage
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    copied!<p>I've written a WebSocket client in Javascript that connects and shakes hands with C# my server. Currently, upon 'Flushing' my output stream ( only after I have sent the header BACK to the client and affirmed my connection ), the client crashes and generates a server-side exception when I try to write the next time around. The latter behavior is expected, however what I can't figure out is why the flush would drop the connection. I'm using a TcpListener and a Socket with a StreamWriter on the server end, and a plain WebSocket on the client. </p> <p>What is truly perplexing about this scenario is that during transmission of the 'handshake', text can be transmitted both ways and a Flush is executed after each line is sent, but as soon as the handshake is complete, a flush terminates the connection.</p> <p>Please tell me if there is not enough information in this revision; as it has been modified a few times now.</p> <p>Thanks in advance.</p> <p>Client Javascript:</p> <pre><code>&lt;!DOCTYPE html&gt; &lt;meta charset="utf-8" /&gt; &lt;html&gt; &lt;head&gt; &lt;script language="javascript" type="text/javascript"&gt; var wsUri = "ws://127.0.0.1:9002/cc"; var output; var websocket = null; function init() { StartWebSocket(); } function StartWebSocket() { output = document.getElementById("output"); writeToScreen("#WebSocket Starting"); websocket = new WebSocket(wsUri,"lorem.ipsum.com"); writeToScreen("#WebSocket Instantiated"); websocket.removeEventListener("open",onOpen,false); websocket.addEventListener("open",onOpen,false); websocket.removeEventListener("close",onClose,false); websocket.addEventListener("close",onClose,false); websocket.removeEventListener("message",onMessage,false); websocket.addEventListener("message",onMessage,false); websocket.removeEventListener("error",onError,false); websocket.addEventListener("error",onError,false); writeToScreen("#WebSocket Events Attached"); } function onOpen(evt) { try { writeToScreen("#WebSocket Connection Established"); writeToScreen("#WebSocket BinaryType: " + websocket.binaryType); writeToScreen("#WebSocket Protocol: " + websocket.protocol); writeToScreen("#WebSocket Extensions: " + websocket.extensions); doSend("TestOutput\r\n\r"); } catch( e ) { writeToScreen(e); } } function onClose(evt) { writeToScreen("#WebSocket Connection Aborted:"); writeToScreen("&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Reason: " + evt.code ); writeToScreen("&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Reason: " + evt.reason ); writeToScreen("&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;Clean: " + evt.wasClean); } function onMessage(evt) { writeToScreen("#WebSocket Message Event"); try { writeToScreen("&lt;span style=\"color: blue;\"&gt;#WebSocket Server Message: " + evt.data+"&lt;/span&gt;"); } catch( e ) { writeToScreen(e); } } function onError(evt) { writeToScreen("&lt;span style=\"color: red;\"&gt;#WebSocket Error:&lt;/span&gt; " + evt.data); } function doSend(message) { try { websocket.send(message); writeToScreen("#WebSocket Output Written to Server: " + message); } catch( e ) { writeToScreen(e); } } function writeToScreen(message) { try { var pre = document.createElement("a"); pre.style.wordWrap = "break-word"; pre.innerHTML = message + "&lt;br&gt;"; output.appendChild(pre); } catch( e ) { writeToScreen(e); } } window.addEventListener("load", init, false); &lt;/script&gt; &lt;/head&gt; &lt;body&gt; &lt;div id="output"&gt;&lt;/div&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>The handshake offer I recieve from my client is as follows:</p> <pre><code>GET /cc HTTP/1.1 Upgrade: websocket Connection: Upgrade Host: 127.0.0.1:9002 Origin: http://localhost Sec-WebSocket-Key: icajBpkAfgA+YbVheBpDsQ== Sec-WebSocket-Version: 13 </code></pre> <p>I interpret the handshake like so:</p> <pre><code>public override void Interpret(string Argument) { if (String.IsNullOrEmpty(Argument)) { return; } else { if( !HeaderFinished ) { if (!HeaderStarted) { if (Argument.StartsWith("GET /")) { this.Role = "client"; HeaderStarted = true; this.Server.Print("Connection at " + this.Address + " set to client."); } else { return; } } else { if (Argument.StartsWith("Sec-WebSocket-Key:")) { this.Key = Argument.Split(' ')[1].TrimEnd().TrimStart(); return; } else if (Argument.StartsWith("Sec-WebSocket-Version:")) { this.HeaderFinished = true; this.WriteHeaderResponse(); HeaderSent = true; return; } } } else { this.InterpretMessage(DecodeMessage(Argument)); return; } } } </code></pre> <p>Send my Header Response:</p> <pre><code>public void WriteHeaderResponse() { this.WriteLine("HTTP/1.1 101 Switching Protocols"); this.WriteLine("Upgrade: websocket"); this.WriteLine("Connection: Upgrade"); String NewKey = ComputeResponseKey(this.Key); this.WriteLine("Sec-WebSocket-Accept: " + NewKey); this.WriteLine("Sec-WebSocket-Protocol: lorem.ipsum.com"); this.WriteLine("\r\n"); } </code></pre> <p>And get the following output from the client ( at this point ):</p> <pre><code>#WebSocket Starting #WebSocket Instantiated #WebSocket Events Attached #WebSocket Connection Established #WebSocket BinaryType: blob #WebSocket Protocol: lorem.ipsum.com #WebSocket Extensions: #WebSocket Output Written to Server: TestOutput </code></pre> <p>At this point, if I attempt to execute the following server-side method, the client disconnects like so:</p> <pre><code>#WebSocket Connection Aborted: Reason: 1006 Reason: Clean: false </code></pre> <p>Message Code: -Taken from something I found on the net, modified a bit...</p> <pre><code>public void WriteMessage(byte[] Payload) { byte[] Message; int Length = Payload.Length; int MaskLength = 4; if (Length &lt; 126) { Message = new byte[2 + MaskLength + Length]; Message[1] = (byte)Length; } else if (Length &lt; 65536) { Message = new byte[4 + MaskLength + Length]; Message[1] = (byte)126; Message[2] = (byte)(Length / 256); Message[3] = (byte)(Length % 256); } else { Message = new byte[10 + MaskLength + Length]; Message[1] = (byte)127; int left = Length; int unit = 256; for (int i = 9; i &gt; 1; i--) { Message[i] = (byte)(left % unit); left = left / unit; if (left == 0) break; } } //Set FIN Message[0] = (byte)129;// (0 | 0x80); //Set mask bit //Message[1] = (byte)(Message[1] | 0x80); //GenerateMask(Message, Message.Length - MaskLength - Length); //if (Length &gt; 0) //MaskData(Payload, 0, Length, Message, Message.Length - Length, Message, Message.Length - MaskLength - Length); char[] output = new char[Message.Length-4]; for( int i = 0, y = 0, z = 0; i &lt; Message.Length; i++ ) { if (Message[z] == '\0') { if (Payload.Length &gt; i-z) output[i] = (char)Payload[y++]; } else { output[i] = (char)Message[z++]; } } this.OutputWriter.Write(output, 0, output.Length); this.OutputWriter.Flush(); } </code></pre> <p>UPDATE: I just replaced all of the code in this document with my most current.</p> <p>To summarize:</p> <pre><code>- The client-server handshake has been matched on both sides. - A path has been defined in the URI for the WebSocket. - Data packets are now being 'properly' framed. </code></pre> <p>One point I have only noticed while editing this, is the last few lines of my WriteMessage method. After doing all of my framing, I convert my byte array to a character array and use a StreamReader.Write to send it. I'm not sure if this is a viable solution or not, so please put me in check if it's not.</p> <p>Otherwise I am baffled. This seems to comply to all of the standards that I have read anything about, but still fails me miserably. This is quite the deal-maker if I can get it working, so I really do appreciate anyone's help.</p> <p>Thank you. -DigitalJedi <em>facepalm</em></p>
 

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