The source code in CVS currently represents a later version than what is in the archive. To use test code from CVS you need to get the implementation code from CVS and build it into a jar file yourself. The build scripts are in CVS too.
Typically on startup of a device it sends out an IAm message, which announces its presence to all other existing devices. It optionally may then send a WhoIs request to discover all other existing devices (if it happens to care). I recommend you look further into these two messages for more information.