[erlang-questions] Push a message to cowboy websockets

Loïc Hoguin essen@REDACTED
Fri Mar 16 17:20:01 CET 2012


The general idea is to have your websocket handler register itself using 
gproc[1] (or through a central gen_server) inside the websocket_init/3 
callback, and then have your service push messages to all registered 
handlers which you can then catch in websocket_info/3.

I mention gproc because it's infinitely easier with it, as you only have 
to register all your processes under one property and then send a 
message to that property which will multicast it to all registered 
processes. And when your websocket closes, gproc takes care of removing 
your process from the list of registered processes, so you really have 
to worry only about 2 lines of code to do everything you need.

Good luck!

[1] https://github.com/uwiger/gproc

On 03/16/2012 05:11 PM, AD wrote:
> Hello,
>   I have cowboy setup and working to send/receive websockets over a
> socket connection.  I am trying to figure out how to initiate a message
> server side over that channel (without it just being a reply).  I am
> envisioning exposing a webservice on the cowboy service that would then
> push a message to all connected users (or maybe a subset based on some
> criteria).
>   Does anyone know if this is possible and if so how to implement?
>   Cheers,
>   -AD
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Loïc Hoguin
Erlang Cowboy
Nine Nines

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