Joel,

Maybe http://www.sysinternals.com/ntw2k/source/tcpview.shtml could help here.

>For some reason, I cannot connect to my computer on the local network from the internet. I have had it working before, but someone must have changed some settings on the computer. Here is some configuration info and what I have tried already:
>
>- I'm using Windows XP Professional, and I intend to use Remote Desktop over the internet. For testing purposes, I am trying to access my local FTP server on port 21.
>
>- I configured our router using NAT to send port 21 to my computer. There is no other firewall on the network, and I confirmed that the personal firewall is turned off.
>
>- I can successfully connect to the FTP server from another computer on the local network. Also, I can route the port to a different FTP server, and then I can connect to that machine from the internet.
>
>- I can see the router creating sending port 21 from the internet to my computer, but my machine does not respond.
>
>So, I think the problem is related to my machine only. Besides a firewall, is there a setting somewhere in Windows XP that tells the computer not to accept connections from the internet or external network? Any other ideas?
>
>Thanks.