Home/ Questions/Q 9219141
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-18T03:02:13+00:00

I’m a beginner with the WebSocket API. I’m trying to connect to my server

  • 0

I’m a beginner with the WebSocket API. I’m trying to connect to my server locally but I’m obtaining the connection closed message. Can anyone tell me what I am doing wrong?

That’s my code:

Server

using System.Net.Sockets;
using System.Net;
using System.IO;
using System;
class Program
{
    static void Main(string[] args)
    {
        var listener = new TcpListener(IPAddress.Loopback, 8181);
    listener.Start();
    while (true)
    {
        Console.WriteLine("Listening...");
        using (var client = listener.AcceptTcpClient())
        using (var stream = client.GetStream())
        using (var reader = new StreamReader(stream))
        using (var writer = new StreamWriter(stream))
        {

            string line = null, key = "", responseKey = "";
            string MAGIC_STRING = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
            while (line != "")
            {
                line = reader.ReadLine();
                if (line.StartsWith("Sec-WebSocket-Key:"))
                {
                    key = line.Split(':')[1].Trim();
                }
            }

            if (key != "")
            {
                key += MAGIC_STRING;
                using (var sha1 = SHA1.Create())
                {
                    responseKey = Convert.ToBase64String(sha1.ComputeHash(Encoding.ASCII.GetBytes(key)));
                }
            }

            // send handshake to the client
            writer.WriteLine("HTTP/1.1 101 Web Socket Protocol Handshake");
            writer.WriteLine("Upgrade: WebSocket");
            writer.WriteLine("Connection: Upgrade");
            writer.WriteLine("WebSocket-Origin: http://localhost:8080");
            writer.WriteLine("WebSocket-Location: ws://localhost:8181/websession");
            if (!String.IsNullOrEmpty(responseKey))
                writer.WriteLine("Sec-WebSocket-Accept: " + responseKey);
            writer.WriteLine("");
            Console.ReadLine();
            writer.Flush();

        }//using
        Console.WriteLine("Finished");
    }//while

    }
}

The Client

     <!DOCTYPE HTML>
       <html>
       <head><title></title>
          <script type="text/javascript">

       function WebSocketTest() {
          var msg = document.getElementById("msg");
            if ("WebSocket" in window) {
             msg.innerHTML="WebSocket is supported by your Browser!";
        // Let us open a web socket
        var ws = new WebSocket("ws://localhost:8181/websession");
        ws.onopen = function () {
            // Web Socket is connected, send data using send()
             msg.innerHTML="connection open";
            //ws.send("Message to send");
            //msg.innerHTML="Message is sent...";
        };
        ws.onclose = function () {
            // websocket is closed.
            msg.innerHTML = "Connection is closed...";
        };

        ws.onerror = function(error){
            console.log('Error detected: ' + error);
        };
        ws.onmessage = function (evt) {
            var received_msg = evt.data;
            msg.innerHTML="Message is received...";
        };

    }
    else {
        // The browser doesn't support WebSocket
        msg.innerHTML="WebSocket NOT supported by your Browser!";
    }
   }
   </script>
     </head>
       <body>
       <div id="sse">
        <a href="javascript:WebSocketTest()">Run WebSocket</a><br />
         <p id="msg"></p>
       </div>
        </body> 
           </html>

Any solution would be appreciated and thank you 🙂

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    That is not a valid web-socket response under any specification. The initial web-socket response always requires you to crunch some numbers as part of the response headers, to prove you’re a web-socket server. Which headers to read and write, and what crunching to do, depends on the version of web-sockets (hibi/hixie 76/rfc). It actually looks like your server is using the headers of a client.

    For example, a RFC6455 (13) response would start:

    HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: {crunch some numbers}

    Note that a Hixie-76 response is different, and there are bits in the above that I have omitted.

    From the RFC6455 specification:

    To prove that the handshake was received, the server has to take two
    pieces of information and combine them to form a response. The first
    piece of information comes from the |Sec-WebSocket-Key| header field
    in the client handshake:

     Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==

    For this header field, the server has to take the value (as present in
    the header field, e.g., the base64-encoded [RFC4648] version minus any
    leading and trailing whitespace) and concatenate this with the
    Globally Unique Identifier (GUID, [RFC4122]) "258EAFA5-E914-47DA-
    95CA-C5AB0DC85B11" in string form, which is unlikely to be used by
    network endpoints that do not understand the WebSocket Protocol. A
    SHA-1 hash (160 bits) [FIPS.180-3], base64-encoded (see Section 4 of
    [RFC4648]), of this concatenation is then returned in the server’s
    handshake.

    • 0