WebSocket channels in Python

This is a simple WebSocket server written in Python using Flask + gevent-websocket.

Inspired by https://devcenter.heroku.com/articles/python-websockets and https://github.com/kennethreitz/flask-sockets

The middleware is not Flask specific, it can be used around any WSGI application.

The server uses Redis Pub/Sub subsystem to ensure that all connected clients recieve the message, even if there are several Gunicorn workers/machines:

$ gunicorn chat:websockets --config=gunicorn_settings.py --workers=2 --worker-connections=2

2015-01-03 11:09:03 [30648] [INFO] Starting gunicorn 19.1.1
2015-01-03 11:09:03 [30648] [INFO] Listening at: http://127.0.0.1:5000 (30648)
2015-01-03 11:09:03 [30648] [INFO] Using worker: websocket_channels.Worker
2015-01-03 11:09:03 [30653] [INFO] Booting worker with pid: 30653
2015-01-03 11:09:03 [30654] [INFO] Booting worker with pid: 30654
2015-01-03 11:09:08 [30653] [INFO] Pusblishing message to channel chat: {"handle":"","text":"test"}
2015-01-03 11:09:08 [30654] [INFO] Sending message to clients on channel chat: {"handle":"","text":"test"}
2015-01-03 11:09:08 [30653] [INFO] Sending message to clients on channel chat: {"handle":"","text":"test"}

Running the server:

$ gunicorn chat:websockets --config=gunicorn_settings.py

You can send a message to a channel (after visiting http://127.0.0.1:5000/channel/users/1 ) using an HTTP POST request:

$ curl 'http://localhost:5000/publish' -d '{"users/1": "Hi user 1!"}'

You can send a message to all sub-channels using trailing slash:

$ curl 'http://localhost:5000/publish' -d '{"users/": "Hi to all users!"}'

Sample Nginx conf:

upstream websocket {
    server 127.0.0.1:5000;
}

server {
    ...

    location ~ /ws/(?<rest>.+) {
        proxy_pass http://websocket/$rest;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
    }
}

Then in Chrome Console you could do something like:

> $.getScript('//rawgit.com/joewalnes/reconnecting-websocket/master/reconnecting-websocket.js');
< Object {readyState: 1, getResponseHeader: function, getAllResponseHeaders: function, setRequestHeader: function, overrideMimeType: function…}
> var socket = new ReconnectingWebSocket("ws://"+ location.host + "/ws/channel");
< undefined
> socket.onmessage = function(message) { console.log(message.data); };
< function (message) { console.log(message.data); }

And send a message to the browser:

$ curl 'http://localhost:5000/channel' -d '{"text": "Hi there!"}'