0.3/ModPythonChat – Orbited – Networking for the Web

Warning!

This page applies to an older version of Orbited (Version 0.3) For info on the current version see the main documentation.

Goal

By the end of this tutorial, you will have created a comet-based chat application using Orbited and mod_python.

Prerequisites

1. Orbited makes it easy to write comet-based web applications

To install, please see the Installation tutorial

2. PyOrbited lets you use Python with Orbited

To install, use easy_install.

  easy_install pyorbited

For more information about PyOrbited, see the tutorial Using Python with Orbited.

3. mod_python embeds the Python interpreter in your Apache server.

Python-based web applications run significantly faster with mod_python. After downloading the module, you need to configure your Apache server. For a refresher on using mod_python, see the following tutorial.

Daemon

1. Configure daemon

Create a file called orbited.cfg in the directory from which you will start Orbited and add these contents:

  [global]
  proxy.enabled = 1
  proxy.keepalive = 0

  [proxy]
  /orbited -> ORBITED
  / -> http://localhost

The configuration file tells the proxy to redirect /orbited requests to our Orbited daemon and redirect all other requests to the Apache server. If your Apache server is listening to a different port such as 8080, you need to specify the port in the configuration file:

  / -> http://localhost:8080

2. Start daemon

Change to the directory containing the configuration file orbited.cfg that you created in step one. Start the daemon by typing the following command:

  orbited

3. Access daemon through proxy

The orbited proxy defaults to listening on port 8000, so make sure that all requests to the Orbited daemon specify port 8000.

Python

Create a file called chat.py in your web directory and add the following content. Note that we retrieve orbited.js from the Orbited daemon. You should set localhost:8000 to the address and port of your Orbited daemon.

  # Get a reference to the Orbited daemon
  from pyorbited.simple import Client
  orbited = Client()
  orbited.connect()

  # Initialize a list of chat users
  users = []

  # Return a list of userKeys for use with orbited.event()
  def __getUserKeys():
      return ['%s, %s, /orbited' % (user, session) for user, session in users]

  # Add the user to the list of users
  def join(req):
      user = req.form.getfirst('user')
      session = req.form.getfirst('session','0')
      if (user, session) not in users:
          users.append((user, session))
          orbited.event(__getUserKeys(), '<b>%s joined</b>' % user)

  # Send the message to all users
  def message(req):
      user = req.form.getfirst('user')
      session = req.form.getfirst('session', '0')
      message = req.form.getfirst('message')
      orbited.event(__getUserKeys(), '<b>%s</b> %s' % (user, message))

  # Set localhost:8000 to the address and port of your Orbited daemon
  html_chat = """\
  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
  <html>
    <head>
      <script src=http://localhost:8000/_/orbited.js></script>
      <script src=chat.js></script>
    </head>
    <body>
      <table>
        <tr>
          <td>Nickname</td>
          <td><input id=nickname></td>
          <td><input type=button value=Connect onclick=connect()></td>
        </tr>
        <tr>
          <td>Message</td>
          <td><input id=chat></td>
          <td><input type=submit value=Send onclick=sendMessage()></td>
        </tr>
      </table>
      <div id=box></div>
    </body>
  </html>"""

  # Return the main chat page
  def index(req):
      return html_chat

Javascript

Create a file called chat.js in your web directory and add the following content:

  // Prevent caching in Internet Explorer
  var ie_nocache = 1;

  // Get request object
  function create_xhr() {
      return window.ActiveXObject ? new ActiveXObject('Microsoft.XMLHTTP') : new XMLHttpRequest();
  }

  // Connect to the Orbited daemon and specify chat_event as the callback
  function connect() {
      var name = document.getElementById('nickname').value;
      Orbited.connect(chat_event, name, '/orbited', '0');
      join(name);
  }

  // The Orbited daemon will call this method when this user receives an event
  function chat_event(data) {
      var chat_box = document.getElementById('box');
      var div = window.parent.document.createElement('div');
      div.className = 'event';
      div.innerHTML = data;
      chat_box.appendChild(div);
  }

  // Adds the user
  function join(user) {
      var xhr = create_xhr();
      xhr.open('GET', '/chat/join?user=' + user, true);
      xhr.send(null);
      // Disable connect button
      document.getElementById('nickname').disabled = true;
      document.getElementById('button_connect').disabled = true;
  }

  // Sends the message
  function sendMessage() {
      ie_nocache += 1;
      var xhr = create_xhr();
      var msg = document.getElementById('chat').value;
      var name = document.getElementById('nickname').value;
      xhr.open('GET', '/chat/message?ie_nocache=' + ie_nocache + '&user=' + name + '&message=' + msg, true);
      xhr.send(null);
  }

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