Presence service

http://forums.java.net/jive/thread.jspa?messageID=226543

Using discovery for presence is not a good idea. I was told so also by a JXTA guru that shall remain unnamed
His recommendation to me which I plan to follow is to simply use a bidipipe connection. that is, keep a list of peers you want to keep track of, let them have a public bidipipe always available and simply connect and disconnect from that pipe at regular intervals. You do not need to implement more than that since a connection to the pipe confirm presence of that peer. No actual communication need to take place.
It may not be pretty but it will get the job done.
Hope it helps.