Two fellow students and I have been working on a protocol, a dotNet client and a java Client designed to allow Instant Messaging on a LAN without any server being needed.
This very simple protocol uses UDP multicasting possibility for peer discovery. AES is also used for basic encryption of all text exchanged against eavesdropping.
The protocol is currently in version 2.0, and the dotNet client for this version is usable. Thus we have decided to release a version.
The binaries, source-code and documentations are available on sourceforge.net at: