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<!DOCTYPE html>
<html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<h1>WebSockets</h1>
<p>A WebSocket is a <a href="http://tools.ietf.org/html/rfc6455">standard protocol</a> for
two-way communication between servers and clients. The WebSockets protocol does
not run over HTTP, instead it is a separate implementation on top of
<a href="http://en.wikipedia.org/wiki/Transmission_Control_Protocol">TCP</a>.</p>
<h2>Why use WebSockets?</h2>
<p>WebSockets allow two-way communication between the client and server.
A WebSockets-enabled application allows a web server to push data to a web
browser without the browser having to poll for updates via HTTP. Allowing
push from the server to the client and vice versa is much more efficient than
having the client constantly ask the server "are there any updates?".</p>
<p>Previous approaches for for keeping a connection alive between client and
server over HTTP, such as
[Comet](http://en.wikipedia.org/wiki/Comet_(programming), have either used
long polling or were not implemented by all browsers.</p>
<h2>JavaScript client libraries</h2>
<ul>
<li>
<p><a href="http://socket.io/">Socket.io</a>'s client side JavaScript library can be
used to connect to a server side WebSockets implementation.</p>
</li>
<li>
<p><a href="https://github.com/gimite/web-socket-js">web-socket-js</a> is a Flash-based
client-side WebSockets implementation.</p>
</li>
</ul>
<h2>Websockets with Nginx</h2>
<p>Nginx officially supports WebSocket proxying as of
<a href="http://nginx.com/blog/websocket-nginx/">version 1.3</a>. However, you have
to configure the Upgrade and Connection headers to ensure requests are
passed through Nginx to your WSGI server. It can be tricky to set this up
the first time. The following resources are helpful for setting up the
configuration properly.</p>
<ul>
<li>
<p>Nginx has <a href="http://nginx.org/en/docs/http/websocket.html">an official page for WebSocket proxying</a>.</p>
</li>
<li>
<p><a href="http://blog.martinfjordvald.com/2013/02/websockets-in-nginx/">WebSockets in Nginx</a>
walks through the Nginx WebSockets configuration directives.</p>
</li>
<li>
<p><a href="https://chrislea.com/2013/02/23/proxying-websockets-with-nginx/">Proxying WebSockets with Nginx</a>
shows how to proxy with Socket.io.</p>
</li>
</ul>
<h2>Open source Python examples with WebSockets</h2>
<ul>
<li>
<p>The
<a href="https://github.com/makaimc/python-websockets-example">python-websockets-example</a>
contains code to create a simple web application that provides WebSockets
using Flask, Flask-SocketIO and gevent.</p>
</li>
<li>
<p>The Flask-SocketIO project has a
<a href="https://github.com/miguelgrinberg/Flask-SocketIO/tree/master/example">chat web application</a>
that demos sending server generated events as well as input from users
via a text box input on a form.</p>
</li>
</ul>
<h2>General WebSockets resources</h2>
<ul>
<li>
<p>The official W3C
<a href="http://www.w3.org/TR/websockets/">candidate draft for WebSockets API</a>
and the
<a href="http://dev.w3.org/html5/websockets/">working draft for WebSockets</a> are
good reference material but can be tough for those new to the WebSockets
concepts. I recommend reading the working draft after looking through some
of the more beginner-friendly resources list below.</p>
</li>
<li>
<p><a href="http://lucumr.pocoo.org/2012/9/24/websockets-101/">WebSockets 101</a> by
Armin Ronacher provides a detailed assessment of the subpar state of HTTP
proxying in regards to WebSockets. He also discusses the complexities of
the WebSockets protocol including the packet implementation.</p>
</li>
<li>
<p>The "Can I Use?" website has a
<a href="http://caniuse.com/#feat=websockets">handy WebSockets reference chart</a>
for which web browsers and specific versions support WebSockets.</p>
</li>
<li>
<p>Mozilla's
<a href="https://developer.mozilla.org/en-US/docs/WebSockets">Developer Resources for WebSockets</a>
is a good place to find documentation and tools for developing with
WebSockets.</p>
</li>
</ul>
<h2>Python-specific WebSockets resources</h2>
<ul>
<li>
<p><a href="http://mrjoes.github.io/2013/06/21/python-realtime.html">Real-time in Python</a>
provides Python-specific context for how the server push updates were
implemented in the past and how Python's tools have evolved to perform
server side updates.</p>
</li>
<li>
<p>The <a href="https://www.twilio.com/blog/2014/11/choose-your-own-adventure-presentations-with-reveal-js-python-and-websockets.html">Choose Your Own Adventure Presentations</a>
tutorial uses WebSockets via gevent on the server and socketio.js for
pushing vote count updates from the server to the client. </p>
</li>
<li>
<p><a href="http://bottlepy.org/docs/dev/async.html">Async with Bottle</a> shows how to
use greenlets to support WebSockets with the Bottle web framework.</p>
</li>
<li>
<p>If you're deploying to Heroku, there is a
<a href="https://devcenter.heroku.com/articles/python-websockets">specific WebSockets guide</a>
for getting your Python application up and running.</p>
</li>
</ul>
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<a href="/">Full Stack Python</a> is an open book that explains
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