We will start by adding the Python code needed to handle channels on the server side. We expect the JavaScript client will make an HTTP GET request to request a channel, so we add a request handler that will create a channel and return a token in the JSON format to access it. We first import the modules needed at the top of our main.py module:

from google.appengine.api import channel
from utils import get_notification_client_id
import json

Then, we add the code for the request handler:

class GetTokenHandler(webapp2.RequestHandler):
    def get(self):
        user = users.get_current_user()
        if user is None:
            self.abort(401)

        client_id = get_notification_client_id(user)
        token = channel.create_channel(client_id, 60)

        self.response.headers['Content-Type'] = 'application/json'
        self.response.write(json.dumps({'token': token}))

We first check that the user is logged in and return an HTTP 401: Unauthorized error page if this...