Written as a mid-level programming guide, this book provides Java programmers with the information and tools needed to create their own Instant Messenger client and server software. This software can then be used to create personalized IM systems or integrate IM features into existing software. Focus is given to the open source Jabber XML-based IM protocols to create Java IM software. These open protocols allow IM software to seamlessly communicate with the larger number of other Jabber clients and servers available including commercial Jabber systems such as Disney's go.com IM.