Gevent-socketio documentation¶
Introduction¶
Socket.IO is a WebSocket-like abstraction that enables real-time
communication between a browser and a server. gevent-socketio
is a
Python implementation of the protocol.
The reference server implementation of Socket.IO runs on Node.js and was developed by LearnBoost. There are now server implementations in a variety of languages.
One aim of this project is to provide a single gevent
-based
API that works across the different WSGI-based web frameworks out
there (Pyramid, Pylons, Flask, web2py, Django, etc...). Only ~3 lines
of code are required to tie-in gevent-socketio
in your framework.
Note: you need to use the gevent
python WSGI server to use
gevent-socketio
.
Namespaces: since you mostly have one websocket/socket.io endpoint per website, it is important to be able to namespace the different real-time activities of the different pages or parts of your site, just like you need routes to map URLs to different parts of your code. The Socket.IO 0.7+ namespaces are a welcome addition, and if you don’t use Socket.IO, you’ll probably end-up writing your own namespacing mechanism at some point.
Named events: To distinguish the messages that are coming and
going, you most probably want to give them some name. Here again, not
using Socket.IO, you will find yourself implementing a way to tag your
packets with names representing different tasks or actions to
perform. With Socket.IO 0.6 or with normal WebSockets, you would
probably encode a JSON object with one of the keys that is reserved
for that (I used {"type": "submit_something"}
. Socket.IO 0.7+
implements named events, which put that information in a terse form on
the wire. It also allows you to define callbacks, that can be
acknowledged by the other endpoint, and then fire back your function
with some return parameters. Something great for RPC, that you’d need
to implement yourself the moment you need it.
Transports: One of the main feature of Socket.IO is the
abstraction of the transport, that gives you real-time web support
down to Internet Explorer 6.0, using long-polling methods. It will
also use native WebSockets when available to the browser, for even
lower latencies. Currently supported transports: websocket
,
flashsocket
, htmlfile
, xhr-multipart
, xhr-polling
,
jsonp-polling
.
This implementation covers nearly all the features of the Socket.IO 0.7+ (up to at least 0.9.1) protocol, with events, callbacks. It adds security in a pythonic way with granular ACLs (which don’t exist in the Node.js version) at the method level. The project has several examples in the source code and in the documentation. Any addition and fixes to the docs are warmly welcomed.
Concepts¶
In order to understand the following documentation articles, let’s clarify some of the terms used:
A Namespace is like a controller in the MVC world. It encompasses
a set of methods that are logically in it. For example, the
send_private_message
event would be in the /chat
namespace, as
well as the kick_ban
event. Whereas the scan_files
event
would be in the /filesystem
namespace. Each namespace is
represented by a sub-class of BaseNamespace
. A simple
example would be, on the client side (the browser):
var socket = io.connect("/chat");
having loaded the socket.io.js
library somewhere in your <head>.
On the server (this is a Pyramid example, but its pretty much the same
for other frameworks):
from socketio.namespace import BaseNamespace
class ChatNamespace(BaseNamespace):
def on_chat(self, msg):
self.emit('chat', msg)
def socketio_service(request):
socketio_manage(request.environ, {'/chat': ChatNamespace},
request)
return "out"
Here we use socketio.socketio_manage()
to start the Socket.IO
machine, and handle the real-time communication.
You will come across the notion of a Socket
. This is a virtual
socket, that abstracts the fact that some transports are long-polling
and others are stateful (like a Websocket), and exposes the same
functionality for all. You can have many namespaces inside a Socket,
each delimited by their name like /chat
, /filesystem
or
/foobar
. Note also that there is a global namespace, identified
by an empty string. Some times, the global namespace has special
features, for backwards compatibilty reasons (we only have a global
namespace in version 0.6 of the protocol). For example, disconnecting
the global namespace means disconnect the full socket. Disconnecting
a qualified namespace, on the other hand, only removes access to that
namespace.
The Socket
is responsible from taking the packets, which are, in
the realm of a Namespace
or a Socket
object, a dictionary that
looks like:
{"type": "event",
"name": "launch_superhero",
"args": ["Superman", 123, "km", {"hair_color": "brown"}]}
These packets are serialized in a compact form when its time to put them on the wire. Socket.IO also has some optimizations if we need to send many packets on some long-polling transports.
At this point, if you don’t know gevent
, you probably will want to
learn a bit more about it, since it is the base you will be working
on:
Getting started¶
Until we have a fully-fledged tutorial, please check out our example applications and the API documentation.
You can see a video that shows gevent-socketio
in a live coding
presentation here:
To learn how to build your Namespace (the object dealing with requests and replies), see:
See this doc for different servers integration:
Examples¶
The gevent-socketio
repository holds several examples:
https://github.com/abourget/gevent-socketio/tree/master/examples
simple_chat
is a bare-bone WSGI app with a minimal socketio integrationsimple_pyramid_chat
is a simple chat application built on Pyramidlive_cpu_graph
is a simple realtime CPU graph (linux only)twitter_stream
is a streaming feed of twitter updatespyramid_backbone_redis_chat
is a Pyramid app using backbone.js and redis for pubsubpyramid_backbone_redis_chat_persistence
is a Pyramid app using backbone.js, redis for pubsub and features persistencetestapp
is the app we use to test the different features, so there are a couple of more advanced use-cases demonstrated there
pyvore
is an application that was developed to serve as real-time
chat in conferences like the PyCon:
This app is a Django tic-tac-toe application that uses the latest
gevent-socketio
:
Security¶
gevent-socketio
provides method-level security, using an ACL
model. You can read more about it in the socketio.namespace, but
a basic example to secure one namespace would look like:
class AdminInterface(BaseNamespace):
def get_initial_acl(self):
"""Everything is locked at first"""
return []
def initialize(self):
# This here assumes you have passed in a `request`
# to your socketio_manage() call, it has that
# `is_admin` attribute
if not request.is_admin:
return
else:
self.lift_acl_restrictions()
def on_blahblahblah(self, data):
"""This can't be access until `lift_acl_restrictions()` has
been called
"""
pass
API docs¶
API documentation is where most of the juice/meat is. Read through
and you’ll (hopefully) understand everything you need about
gevent-socketio
.
The manager is the function you call from your framework. It is in:
socketio
Namespaces are the main interface the developer is going to use. You mostly define your own BaseNamespace derivatives, and gevent-socketio maps the incoming messages to your methods automatically:
socketio.namespace
Mixins are components you can add to your namespaces, to provided added functionality.
socketio.mixins
Sockets are the virtual tunnels that are established and abstracted by the different Transports. They basically expose socket-like send/receive functionality to the Namespace objects. Even when we use long-polling transports, only one Socket is created per browser.
socketio.virtsocket
Packet is a library that handle the decoding of the messages encoded in the Socket.IO dialect. They take dictionaries for encoding, and return decoded dictionaries also.
socketio.packet
Handler is a lower-level transports handler. It is responsible for calling your WSGI application
socketio.handler
Transports are responsible for translating the different fallback mechanisms to one abstracted Socket, dealing with payload encoding, multi-message multiplexing and their reverse operation.
socketio.transports
Server is the component used to hook Gevent and its WSGI server to the WSGI app to be served, while dispatching any Socket.IO related activities to the handler and the transports.
socketio.server
Auto-generated indexes:
References¶
LearnBoost’s node.js version is the reference implementation, you can find the server component at this address:
The client JavaScript library’s development branch is here:
The specifications to the protocol are somehow in this repository:
This is the original wow-website:
Here is a list of the different frameworks integration to date, although not all have upgraded to the latest version of gevent-socketio:
- pyramid_socketio: https://github.com/abourget/pyramid_socketio
- django-socketio: https://github.com/stephenmcd/django-socketio
The Flask guys will be working on an integration layer soon.
Contacts¶
For any questions, you can use the Issue tracking at Github:
The mailing list:
The maintainers:
Credits¶
Jeffrey Gellens for starting and polishing this project over the years.
PyCon 2012 and the Sprints, for bringing this project up to version 0.9 of the protocol.
Current maintainers:
- Alexandre Bourget
- John Anderson
Contributors:
- Denis Bilenko
- Bobby Powers
- Lon Ingram
- Eugene Baumstein
- Sébastien Béal
- jpellerin (JP)
- Philip Neustrom
- Jonas Obrist
- fabiodive
- Dan O’Neill
- Whit Morriss
- Chakib (spike) Benziane
- Vivek Venugopalan
- Vladimir Protasov
- Bruno Bigras
- Gabriel de Labacheliere
- Flavio Curella
- thapar
- Marconi Moreto
- sv1jsb
- Cliff Xuan
- Matt Billenstein
- Rolo
- Anthony Oliver
- Pierre Giraud
- m0sth8
- Daniel Swarbrick
TODO¶
How to integrate your framework’s “session” object (Beaker, memcached, or file-based). Beware: this can be tricky. You need to manage that yourself.