Hi!
The Problem is, your client has to know at least one IP of an other client, so it can log into the Gnutella-Net!

There are (at least) two ways:

Hostchacher
A Hostcacher collects IPs from Clients, and send them to your client at startup!

A List of IPs
Some Clients generate a list of known IPs, and uses them on startup

Some clients do both!

Hope it helps.
(If there is somethong wrong, Moak will shurly correct it!)