I have been trying to set up the ARD 3.1 software at my home and at the office so that I can share files effortlessly from one to the other. However at home I have a cable modem with a Lynksys router. The router is set as a gateway and dishes out DHCP to three sub computers so they can share the one static IP address given to me by comcast cable.
I have found the solution. There is a piece of software called lighthouse that will forward the ARD active port traffic to the gateway. And I have configured the gateway to forward the port traffic to the computer. It sounds more complicated than it really is.
At the office I have a static IP address so that is not a problem. But I did find out that ARD will not allow you to change the port setting it runs on. ARD runs on port 3283 or 5900.
Lighthouse by Codelaide Software is a great program. It makes all of this possible behind a NAT router. Its well worth the registration price.