How to Find Open/Close Ports and Bypass a Port?

[Andras Simon]

On 7/19/07, Mustafa Qasim <alajal at gmail.com> wrote:
> Hello!
>           I can't use any p2p client. It seems my service provider has
> blocked all ports used by p2p clients. How can i check what ports are open
> on my gateway[Same machine Also configured as transperent-proxy on Squid at
> 10.0.0.1 in my LAN]. Can I configure my p2p client to use an open port for
> communicatoin?

If you have  shell account outside your LAN, you can use nmap or nc
(and probably many other tools) to find out about your open ports. If
you don't, visit http://www.grc.com/ and look for ShieldsUp!

As for p2p, azureus (a bittorrent client) at least lets you configure
which port to use.
(As an aside, I use a port that is blocked both by my router and
iptables on the machine, and azureus still works. I'm not sure if I
should be happy about this.)

Andras