SockJS-tornado server

SockJS-tornado is a Python server side counterpart of SockJS-client browser library running on top of Tornado framework.

Simplified echo SockJS server could look more or less like::

from tornado import web, ioloop
from sockjs.tornado import SockJSRouter, SockJSConnection

class EchoConnection(SockJSConnection):
    def on_message(self, msg):
        self.send(msg)

if __name__ == '__main__':
    EchoRouter = SockJSRouter(EchoConnection, '/echo')

    app = web.Application(EchoRouter.urls)
    app.listen(9999)
    ioloop.IOLoop.instance().start()

(Take look at examples for a complete version).

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SockJS-tornado API

SockJS provides slightly different API than tornado.websocket. Main differences are:

1. Depending on transport, actual client connection might or might not be there. So, there is no self.request and other tornado.web.RequestHandler properties.
2. Changed open callback name to on_open to be more consistent with other callbacks.
3. Instead of write_message, all messages are sent using send method. Just in case, send in tornado.web.RequestHandler sends raw data over the connection, without encoding it.
4. There is handy broadcast function, which accepts list (or iterator) of clients and message to send.

Settings

You can pass various settings to the SockJSRouter, in a dictionary::

MyRouter = SockJSRouter(MyConnection, '/my', dict(disabled_transports=['websocket']))

Following options are supported:

*Name*	*Description*	*Default Value*
session_check_interval	How often sessions are verified, in seconds. Lower the value, more resources sockjs-tornado will use to drop expired sessions, but will be more precise.	1
disconnect_delay	How long does it takes to consider session dead, in seconds.	5
heartbeat_delay	How often sockjs-tornado should send heartbeats to the client, in seconds.	25
disabled_transports	List of disabled transports. Possible values are: 'websocket', 'xhr', 'xhr_streaming', 'jsonp', 'eventsource' and 'htmlfile'	[]
sockjs_url	Location of the sockjs client script. By default points to the SockJS CDN.	http://cdn.sockjs.org/sockjs-0.1.2.min.js

Deployment

sockjs-tornado properly works behind haproxy and it is recommended deployment approach.

Sample configuration file can be found here.

If your log is full of "WARNING: Connection closed by the client", pass no_keep_alive as True to HTTPServer constructor::

HTTPServer(app, no_keep_alive=True).listen(port)

or::

app.listen(port, no_keep_alive=True)