Building the Realtime User Experience

Logging In

The first thing we’ll need to add to this script is the ability for users to sign in. This won’t be a complicated login process; it will only require users to select a username in order to access the system. Using Tornado’s authentication functionality, it would be fairly easy to implement a much more robust login scheme, but that’s overkill for this example.

On the Server Side

To accommodate users logging into the chat application, the Python script is going to need to accept login requests for the form we created before. To do that, we’ll need to expand the list of URL handlers from the main application class. In the chat-server.py file, locate the Application class and make the following highlighted change:

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

This addition tells Tornado to accept requests for /login and direct them to a class called LoginHandler. That class is illustrated next; add it to the chat-server.py file:

class LoginHandler(BaseHandler):
    def post(self):
        # generate a unique ID for each user
        user_id = str(uuid.uuid4()) 
        # get the user_name submitted from the form
        user_name = self.get_argument('username')

        # Add this user to the chat class
        self.chat.add_user(user_id, user_name)

        # We're done, notify the client.
        self.finish(dict(user_id=user_id, user_name=user_name, users=self.chat.users))

This login handler class just does ...