Yup, Jabber would work very well for what you’'re trying to accomplish.
A real good place to start would be to pickup a copy of “Instant Messaging in Java The Jabber Protocols” ( http://www.manning.com/shigeoka/index.html ). The book contains a somewhat limited, but fully functional Java based Jabber server, a simple client and serves as a very good introduction to Jabber as a whole.
For more robust Jabber servers, there are a number of implementations both free and commercial, to chose from, look here to begin with: http://www.jabber.org/admin/serverlist.php
To develop a more robust client, take a look at the Smack API. Even though it is still in beta, the Smack API is a good place to begin since it is a very easy to understand and use.
Other good recourses are:
http://www.jabber.org (particularly the developer conference room)