Port scans need to be done from outside your net if you want to check if the ISP allows those packets through. See if there is something like http://www.dslreports.com/tools for your area.

I'd forgotten about carracho, and it looks like it hasn't been updated for a few years. Guess there are still a few users around though.

Port-blocking (or "packet-shaping") at the ISP level can be pretty fluid and change often, and often the help desk might not be informed what the internet admins are doing. Assuming you have a direct connection to your ISP, just ask them if you can connect to the gnutella network on port 6346.

If you are using a router, then google about opening that port on the router's homepage.

cheers