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geoffb / simple_websocket_client.html
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Super simple websockets client/server using Python. Compatible with the draft 76 challenge/response.

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simple_websocket_client.html
HTML
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<!DOCTYPE html>
<html lang="en">
<head>
	<title>WebSocket Client</title>
	<style>
		#output {
			border: solid 1px #000;
		}
	</style>
</head>
<body>
	
	<form id="form">
		<input type="text" id="message">
		<button type="submit">Send</button>
	</form>
	
	<hr>
	
	<div id="output"></div>
	
	<script>
	
		var inputBox = document.getElementById("message");
		var output = document.getElementById("output");
		var form = document.getElementById("form");
 
		try {
 
			var host = "ws://" + window.location.hostname + ":9876/stuff";
			console.log("Host:", host);
			
			var s = new WebSocket(host);
			
			s.onopen = function (e) {
				console.log("Socket opened.");
			};
			
			s.onclose = function (e) {
				console.log("Socket closed.");
			};
			
			s.onmessage = function (e) {
				console.log("Socket message:", e.data);
				var p = document.createElement("p");
				p.innerHTML = e.data;
				output.appendChild(p);
			};
			
			s.onerror = function (e) {
				console.log("Socket error:", e);
			};
			
		} catch (ex) {
			console.log("Socket exception:", ex);
		}
 
		form.addEventListener("submit", function (e) {
			e.preventDefault();
			s.send(inputBox.value);
			inputBox.value = "";
		}, false)
 
	</script>
 
</body>
</html>
simple_websocket_server.py
Python
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#!/usr/bin/env python
 
import socket, struct, hashlib, threading, cgi
 
def decode_key (key):
	num = ""
	spaces = 0
	for c in key:
		if c.isdigit():
			num += c
	 	if c.isspace():
			spaces += 1
	return int(num) / spaces
 
def create_hash (key1, key2, code):
	a = struct.pack(">L", decode_key(key1))
	b = struct.pack(">L", decode_key(key2))
	md5 = hashlib.md5(a + b + code)
	return md5.digest()
 
def recv_data (client, length):
	data = client.recv(length)
	if not data: return data
	return data.decode('utf-8', 'ignore')
 
def send_data (client, data):
	message = "\x00%s\xFF" % data.encode('utf-8')
	return client.send(message)
 
def parse_headers (data):
	headers = {}
	lines = data.splitlines()
	for l in lines:
		parts = l.split(": ", 1)
		if len(parts) == 2:
			headers[parts[0]] = parts[1]
	headers['code'] = lines[len(lines) - 1]
	return headers
 
def handshake (client):
	print 'Handshaking...'
	data = client.recv(1024)
	headers = parse_headers(data)
	print 'Got headers:'
	for k, v in headers.iteritems():
		print k, ':', v
	digest = create_hash(
		headers['Sec-WebSocket-Key1'],
		headers['Sec-WebSocket-Key2'],
		headers['code']
	)
	shake = "HTTP/1.1 101 Web Socket Protocol Handshake\r\n"
 	shake += "Upgrade: WebSocket\r\n" 
	shake += "Connection: Upgrade\r\n"
	shake += "Sec-WebSocket-Origin: %s\r\n" % (headers['Origin'])
	shake += "Sec-WebSocket-Location: ws://%s/stuff\r\n" % (headers['Host'])
	shake += "Sec-WebSocket-Protocol: sample\r\n\r\n"
	shake += digest
	return client.send(shake)
 
def handle (client, addr):
	handshake(client)
	lock = threading.Lock()
	while 1:
		data = recv_data(client, 1024)
		if not data: break
		data = cgi.escape(data)
		lock.acquire()
		[send_data(c, data) for c in clients]
		lock.release()
	print 'Client closed:', addr
	lock.acquire()
	clients.remove(client)
	lock.release()
	client.close()
	
def start_server ():
	s = socket.socket()
	s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
	s.bind(('', 9876))
	s.listen(5)
	while 1:
		conn, addr = s.accept()
		print 'Connection from:', addr
		clients.append(conn)
		threading.Thread(target = handle, args = (conn, addr)).start()
 
clients = []
start_server()
ccheaton commented

This is helpful for me because I'm trying to learn websockets. A few comments at the top of each file also would help (ports, etc.).

brandonhsiao commented

What does that lock in handle(client, addr) do? Isn't the point of a lock to synchronize several threads? Is that a bug for each thread to have its own lock?

dawsonlp commented

Running Ubuntu/Chromium/31.0.1650.63, the headers that come from the browser when I load the webpage don't include Sec-WebSocket-Key1 and Sec-WebSocket-Key2, they only have Sec-WebSocket-Key, so the python code throws a KeyError exception in handshake(client) when it tries to build a digest.
Is this because of a recent change in Chrome? Has the websocket protocol been updated since this code was published?

dawsonlp commented

Explanation - the draft 76 challenge/response that this implements has been replaced with RFC-6455. Modern browsers don't work with this code as is.

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