Your ISP can do so, your Mac can only if you are running a personal firewall. - I suggest you just start LimeWire, - if it doesn't connect automatically, you probably won't be able to connect that easily.
- You could try using a gnutella.net file (
ftp://whitedragon.dyndns.org/gnutella.net ) containing a list of recently discovered gnutella nodes that you have to copy into your LimeWire.