How to open a TCP port?

[Torsten]

I want to open the TCP port 81.
At the System Preferences - Sharing - Firewall I created a new port (81),
but wenn I start the portscan of the network utility program, "open TCP port: 81" will not appear in the list.
I use the airport extreme with the IP address 10.0.1.1, when I use portscan for this, only "Open TCP Port: 53 domain" is showing.
My iMac G5 has the IP address 10.0.1.3.
Any idea what's wrong?

[Magnus]

Hi Torsten

Just to make sure, are you scanning the iMac's IP (10.0.1.3.) when it says that port (81) is not open?

I don't have an Airport Extreme so I'm not much help when it comes to it, but someone else probably is!

You can run a command that lists what processes checks what ports, perhaps that can help some (got it here):

sudo lsof -nP | grep LIST

[elchemor]

opening a port on the firewall level doesnt always mean its open ! for a port to be open, u need an aplication to be using it ! is there anything which is using the port 81 on ur G5 ?
on top of that, u will need port forwarding, well... in another words, u will need to tell the 10.0.1.1 that it should forward all the traffic coming on the port 81 to the ip which is 10.0.1.3 ! taking that into account, u should always make sure there is an application using that specific port !

[DXB Law]

When you open a port using System Preferences you need to specify the application for which you want the port to be open.

[iDubai]

Man! It's interesting when I read ^^^^ that stuff..... It's Gibberish. lol

I'm sorry for wasting your time reading my post, but I wish i can help!