---

labels: 'Stage-Beta'

summary: Subscribe to pubsub nodes using the HTML5 EventSource API

...

Introduction

------------

[Server-Sent Events](https://en.wikipedia.org/wiki/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

[EventSource

API](https://developer.mozilla.org/en-US/docs/Web/API/EventSource).

EventSource is supported in [most modern

browsers](http://caniuse.com/#feat=eventsource), and for the remainder

there are 'polyfill' compatibility layers such as

[EventSource.js](https://github.com/remy/polyfills/blob/master/EventSource.js)

and [jquery.eventsource](https://github.com/rwldrn/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 [BOSH:

Cross-domain

issues](https://prosody.im/doc/setting_up_bosh#proxying_requests) 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 [HTTP configuration options](https://prosody.im/doc/http) 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 ['Virtual

Hosts'](https://prosody.im/doc/http#virtual_hosts) section of our HTTP

documentation.

Compatibility

-------------

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  0.9     Works

  0.8     Doesn't work

  Trunk   Works

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