django-socketio is a BSD licensed Django application that brings together a variety of features that allow you to use WebSockets seamlessly with any Django project.
django-socketio was inspired by Cody Soyland's introductory blog post on using Socket.IO and gevent with Django, and made possible by the work of Jeffrey Gelens' gevent-websocket and gevent-socketio packages.
The features provided by django-socketio are:
- Installation of required packages from PyPI
- A management command for running gevent's pywsgi server with auto-reloading capabilities
- A channel subscription and broadcast system that extends Socket.IO allowing WebSockets and events to be partitioned into separate concerns
- A signals-like event system that abstracts away the various stages of a Socket.IO request
- The required views, urlpatterns, templatetags and tests for all the above
Note that if you've never installed gevent, you'll first need to install the libevent development library. You may also need the Python development library if not installed. This can be achieved on Debian based sytems with the following command:
$ sudo apt-get install python-dev $ sudo apt-get install libevent-dev
The easiest way to install django-socketio is directly from PyPi using pip or setuptools by running the respective command below, which will also attempt to install the dependencies mentioned above:
$ pip install -U django-socketio
or:
$ easy_install -U django-socketio
Otherwise you can download django-socketio and install it directly from source:
$ python setup.py install
Once installed you can then add django_socketio to your
INSTALLED_APPS and django_socketio.urls to your url conf. The
client-side JavaScripts for Socket.IO and its extensions can then be
added to any page with the socketio templatetag:
<head>
{% load socketio_tags %}
{% socketio %}
<script>
var socket = new io.Socket();
socket.connect();
// etc
</script>
</head>
The runserver_socketio management command is provided which will
run gevent's pywsgi server which is required for supporting the type of
long-running request a WebSocket will use:
$ python manage.py runserver_socketio host:port
Note that the host and port can also configured by defining the following settings in your project's settings module:
SOCKETIO_HOST- The host to bind the server to.SOCKETIO_PORT- The numeric port to bind the server to.
These settings are only used when their values are not specified as
arguments to the runserver_socketio command, which always takes
precedence.
The WebSocket implemented by gevent-websocket provides two methods for
sending data to other clients, socket.send which sends data to the
given socket instance, and socket.broadcast which sends data to all
socket instances other than itself.
A common requirement for WebSocket based applications is to divide
communications up into separate channels. For example a chat site may
have multiple chat rooms and rather than using broadcast which
would send a chat message to all chat rooms, each room would need a
reference to each of the connected sockets so that send can be
called on each socket when a new message arrives for that room.
django-socketio extends Socket.IO both on the client and server to provide channels that can be subscribed and broadcast to.
To subscribe to a channel client-side in JavaScript use the
socket.subscribe method:
var socket = new io.Socket();
socket.connect();
socket.on('connect', function() {
socket.subscribe('my channel');
});
Once the socket is subscribed to a channel, you can then
broadcast to the channel server-side in Python using the
socket.broadcast_channel method:
socket.broadcast_channel("my message")
The django_socketio.events module provides a handful of events
that can be subscribed to, very much like connecting receiver
functions to Django signals. Each of these events are raised
throughout the relevant stages of a Socket.IO request.
Events are subscribed to by applying each event as a decorator to your event handler functions:
from django_socketio.events import on_message
@on_message
def my_message_handler(request, socket, context, message):
...
Each event handler takes at least three arguments: the current Django
request, the Socket.IO socket the event occurred for, and a
context, which is simply a dictionary that can be used to persist
variables across all events throughout the life-cycle of a single
WebSocket connection.
on_connect- occurs once when the WebSocket connection is first established.on_message- occurs every time data is sent to the WebSocket. Takes an extramessageargument which contains the data sent.on_subscribe- occurs when a channel is subscribed to. Takes an extrachannelargument which contains the channel subscribed to.on_unsubscribe- occurs when a channel is unsubscribed from. Takes an extrachannelargument which contains the channel unsubscribed from.on_error- occurs when an error is raised. Takes an extraexceptionargument which contains the exception for the error.on_disconnect- occurs once when the WebSocket disconnects.on_finish- occurs once when the Socket.IO request is finished.
Like Django signals, event handlers can be defined anywhere so long as they end up being imported. Consider adding them to their own module that gets imported by your urlconf, or even adding them to your views module since they're conceptually similar to views.
All events other than the on_connect event can also be bound to
particular channels by passing a channel argument to the event
decorator. The channel argument can contain a regular expression
pattern used to match again multiple channels of similar function.
For example, suppose you implemented a chat site with multiple rooms. WebSockets would be the basis for users communicating within each chat room, however you may want to use them elsewhere throughout the site for different purposes, perhaps for a real-time admin dashboard. In this case there would be two distinct WebSocket uses, with the chat rooms each requiring their own individual channels.
Suppose each chat room user subscribes to a channel client-side using the room's ID:
var socket = new io.Socket();
var roomID = 42;
socket.connect();
socket.on('connect', function() {
socket.subscribe('room-' + roomID);
});
Then server-side the different message handlers are bound to each type of channel:
@on_message(channel="dashboard")
def my_dashboard_handler(request, socket, context, message):
...
@on_message(channel="^room-")
def my_chat_handler(request, socket, context, message):
...
The following setting can be used to configure logging:
SOCKETIO_MESSAGE_LOG_FORMAT- A format string used for logging each message sent via a socket. The string is formatted using interpolation with a dictionary. The dictionary contains all the keys found in Django'srequest["META"], as well asTIMEandMESSAGEkeys which contain the time of the message and the message contents respectively. Set this setting toNoneto disable message logging.
The "hello world" of WebSocket applications is naturally the chat
room. As such django-socketio comes with a demo chat application
that provides examples of the different events and channel features
available. The demo can be found in the example_project directory
of the django_socketio package. Note that Django 1.3 or higher
is required for the demo as it makes use of Django 1.3's
staticfiles app.