Interoperating with a backend via HTTP

Subscribing to a channel

Your backend can receive messages published into channels by specifying a URL where the messages will be published with POST requests, and which channels do you want to subscribe to:

[{carotene, [
    % ... Other configuration options
    {subscribe_url, ""},
    {subscribed_channels, ["general", "room1"]}

subscribe_url will be the URL where the messages will be published.

subscribed_channels is an specification of the names of the channels you want to subscribe your backend to.

The requests received in your app will have the form of a POST requests with two parameters:

  • message: the message that has been published, encoded in JSON.
  • channel: the channel where it has ben been published.


Carotene provides a RESTful API to retrieve information about subscribed channels the backend is subscribed to, presence in channels and publishing messages.

Publishing to a channel

If you perform a POST query to http(s)://mycaroteneserver/api/channels/mychannel/messages with the parameter message, you will publish that message into the channel.

Retrieving a list to subscribed channels

By performing a GET request to http(s)://mycaroteneserver/api/channels you can retrieve a list of the channels the server is subscribed to.

The list will be equivalent to what is specified in the configuration. So, if you have in your configuration an option like

[{carotene, [
    % ... Other configuration options
    {subscribed_channels, ["general", "room1"]}

and if you access to http(s)://mycaroteneserver/api/channels, you will retrieve a list of the channels that have been created and are in the list.

Retrieving presence information for a channel

Performing a GET request to http(s)://mycaroteneserver/api/channels/mychannel/presence you can retrieve a list of the users subscribed to the channel mychannel in all the nodes.