it's always the same problem: in a p2p-network you need to know the ip of another peer, to connect.
then you can ask him, if he knows other peers (ping). and he will tell you what peers he had found so far (pong). thats how gnutella works.

to find your first peer, you can enter a ip you know manually, download a list of peers from the internet, take the list of the last run of your servent or use a host cache (like router.limewire.com:6346 or gnutellahosts.com:6346).

so if you have a very small privat network you will have to enter the ip manually.

btw: why don't you look for the answer yourself?
google is your friend.