C# Websocket server not receiving messages from HTML5 client

Question

I'm attempting to create a bare bones websocket chat room server. My client is able to connect to the server, but it is unable to send messages to the server, despite the server being in a listening state.

When the client connects, a bunch of what looks like header information gets written to the console. But when WebSocket.send() gets executed in Javascript, nothing occurs server side.

HTML:

<button id="closeSocket">disconnect</button><br />
<input id = "inputField" /><button id="sendMessage">send</button>
<div id = "output"></div>

<script type = 'text/javascript' src = 'websockets.js'></script>

Javascript:

websocket = new WebSocket("ws://127.0.0.1:80");

document.getElementById("closeSocket").onclick = closeSocket;
document.getElementById("sendMessage").onclick = sendMessage;

websocket.onopen = function(){
  output("connected");
}

function sendMessage(){
    output("sent: " + document.getElementById('inputField').value);
  websocket.send(document.getElementById('inputField').value);
}

websocket.onmessage = function(e){
  output("got response: " + e.data);
}

function closeSocket(){
    websocket.close();
}

websocket.onclose = function(){
    output("disconnected");
}

function output(t){
    document.getElementById("output").innerHTML += t + "<br />";
}

C# server:

using System;
using System.Net;
using System.Net.Sockets;

namespace WebSocketsTutorial {
    class Program {
        static void Main(string[] args) {
            TcpListener server = new TcpListener(IPAddress.Parse("127.0.0.1"), 80);
            TcpClient client = default(TcpClient);

            server.Start();
            Console.WriteLine("server started");

            while (true) {
                client = server.AcceptTcpClient();

                byte[] receivedBuffer = new byte[100];
                NetworkStream stream = client.GetStream();

                stream.Read(receivedBuffer, 0, receivedBuffer.Length);

                foreach (byte b in receivedBuffer) {
                    Console.Write(Convert.ToChar(b).ToString());
                }
            }
        }
    }
}

This is what is output on the console when the client connects:

What I'm mainly looking to do is to allow an arbitrary number of connections and ultimately have the server echo a user's submission to all connected clients.

Answer 1

First of all, a WebSocket is not just a regular socket. It defines a connection handshake using HTTP and its own framing protocol that you need to use.

https://en.wikipedia.org/wiki/WebSocket

https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API/Writing_WebSocket_servers

https://hpbn.co/websocket/

Second, you are reading just the first 100 bytes of the request. You should read until the Read operation returns 0.

There is a myriad of components you can use to create a WebSocket server, including the default one: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/websockets