You need to tell Colin the hostname that your server can actually be reached on; the hostname is what someone can put into the Advanced connect box on the client to connect to your server.
It needs to be a globally accessible (ie not 127.0.0.1, 192.168.x.x or your local computer name) and, because you probably don't have a fixed external IP address, you need to use a domain name of your own (like shoddy.example.com), or a DynDNS service like the one I linked to above, that points to your server.
Basically, if you can set-up Java to use any random proxy server on the internet and still connect to your server then you have the right hostname.