Most likely your your cable modem or DSL modem is a NAT device. NAT "hides" you true IP address from the Internet. To find out if your setup uses NAT go to my NAT or not page.
To allow you to play DirectX API and some other games you will need to properly forward the ports on your modem or router to the correct computer or place that computer in the DMZ.
The DirectX API was never designed to work with a NAT. You will need to get a free third-party program called DXport and install it on each computer.
You need to forward port 47624 to the host computer.
Maybe.
First consult my list of various modem/routers configurations.
Second you can contact me by email ( ); please remember that I have a life and a real job, that this page and is merely a hobby. If you do contact me make sure you include as much detail as possible about your configuration or problem. I need to know: