Building the Realtime User Experience

Basic Chatting

It looks like a chat application and it allows multiple users to log in, but it has one fatal flaw: users cannot actually send or receive any chat messages. To allow users to send messages, we need to make a couple of changes. The server-side Python code has almost everything needed to support this feature; now it just needs to accept the messages from the web client and funnel them to the other users. Luckily, much of that code is already written.

Chatting on the Server Side

The Python code already has the ability to send generic messages to users via the send_notification method. So the only thing we need to handle basic chatting is to catch messages from the user and funnel them through that method. To do that, we need to add one more URL handler to the array. In the Application.__init__ method of chat-server.py, make the following addition:

class Application(tornado.web.Application):
    def __init__(self):
    # setup the URL handlers
        handlers = [
            (r"/", MainHandler),
            (r"/login/?", LoginHandler),
            (r"/updates/?", UpdateHandler),
            (r"/send/?", SendHandler),
            ]

This code just sets up another URL handler so that Tornado knows which class should respond to requests to the /send URL. That class, SendHandler, will be responsible for accepting the user input, building a message, and sending it to the receiving user. In chat-server.py, add the following code above the Application class:

class SendHandler(BaseHandler): def post(self): # who is the message to and from? to_user_id = self.get_argument('to_user_id') ...