the project  could be done using JXTA, which is a new set of open protocols meant
for connected devices on a network to communicate via P2P.

a good starting point would be www.jxta.org.

In fact i am working on a similar project.

you should learn something of java  networking and mutilthread program.
struts is use in MVC module and it takes servlet/jsp as its lower layer. of
course you can do the same thing as struts  can by servelt/jsp.