The official Gnutella port is 6346 which you can test. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?
If you can't reach the page then the port is blocked.

If the port is blocked due to your modem/router, & you need to do port forwarding then it's best to forward a port separately for each of TCP/UDP.

There is another port test for other ports but it belongs to the Shareaza forums & you need to have your LW open at the same time. Your firewalls also need to be configured. http://home.no.net/tgrumpy/ct/dex.php