A simple Tornado (http://www.tornadoweb.org/en/stable/) WebSocket Server (with Client)

client.js

var ws = new WebSocket("ws://localhost:8888");
ws.onopen = function() {
  ws.send("Hello, world");
};

//When Client Received a Message
ws.onmessage = function(evt) {
  console.log(evt.data);
};

server_socket.py

import tornado.websocket
from tornado.options import define, options

define("port", default=8888, help="run on the given port", type=int)

class WebSocketHandler(tornado.websocket.WebSocketHandler):
    
  def check_origin(self, origin):
    return True

  def open(self):	
    print("WebSocket opened")

  def on_message(self, message):
    self.write_message(u"You said: " + message)

  def on_close(self):
    print("WebSocket closed")

class Application(tornado.web.Application):
  def __init__(self):
    handlers = [
      (r"/", WebSocketHandler)
    ]
    tornado.web.Application.__init__(self, handlers)

def main():
  tornado.options.parse_command_line()
  app = Application()
  app.listen(options.port)
  tornado.ioloop.IOLoop.current().start()

if __name__ == "__main__":
  main()