#summary Subscribe to pubsub nodes using the HTML5 EventSource API

#labels Stage-Beta

= Introduction =

[https://en.wikipedia.org/wiki/Server-sent_events Server-Sent Events] is a simple HTTP/line-based protocol supported in HTML5, making it easy to receive a stream of "events" in realtime using the Javascript [https://developer.mozilla.org/en-US/docs/Web/API/EventSource EventSource API].

EventSource is supported in [http://caniuse.com/#feat=eventsource most modern browsers], and for the remainder there are 'polyfill' compatibility layers such as [https://github.com/remy/polyfills/blob/master/EventSource.js EventSource.js] and [https://github.com/rwldrn/jquery.eventsource jquery.eventsource].

= Details =

Subscribing to a node from Javascript is easy:

{{{

    var source = new EventSource('http://pubsub.example.org:5280/eventsource/mynode');

    source.onmessage = function (event) {

        console.log(event.data); // Do whatever you want with the data here

    };

}}}

== Cross-domain issues ==

The same cross-domain restrictions apply to EventSource that apply to BOSH, and support for CORS is not clearly standardized yet. You may want to proxy connections through your web server for this reason. See [https://prosody.im/doc/setting_up_bosh#proxying_requests BOSH: Cross-domain issues] for more information.

= Configuration =

There is no special configuration for this module. Simply load it onto a pubsub component like so:

{{{

   Component "pubsub.example.org" "pubsub"

       modules_enabled = { "pubsub_eventsource" }

}}}

As it uses HTTP to serve the event streams, you can use Prosody's standard [https://prosody.im/doc/http HTTP configuration options] to control how/where the streams are served.

*Note about URLs:* It is important to get the event streams from the correct hostname (that of the pubsub host). An example stream URL is `http://pubsub.example.org:5280/eventsource/mynode`. If you need to access the streams using another hostname (e.g. `example.org`) you can use the `http_host` option under the Component, e.g. `http_host = "example.org"`. For more information see the [https://prosody.im/doc/http#virtual_hosts 'Virtual Hosts'] section of our HTTP documentation.

= Compatibility =

|| 0.9 || Works ||

|| 0.8 || Doesn't work ||

|| Trunk || Works ||