How to send a notification about an event on the site to the Jabber client or another messenger?

Question

Messengers

Hello.
How is it possible and in which direction to look?
The site has a commenting system. When a user leaves a message, some action must be triggered to notify that the message has been left. For example, you need to send a message to the site administrators Jabber client.
How is such a thing implemented?

Answer 1

https://code.google.com/p/xmpphp/
And then to taste.