The power of JXTA is that it gives you a fully fledge protocol for
creating P2P stuff, the weakness is that it can take a /very/ long time
to learn  how to harness that power.

However the good news is if you search over the jxta.org website you
should find a build that is designed as an entery level version, which
does a lot of the stuff for you and it is pretty powerfull for most
applications and a good way to bend your brain into jxta.