ok, you`ll need to make sure that..
1. you have a static IP allocated to the machine that is running the server.
2. you have port 63392 udp+tcp forwarded to that machine in your router.
If you`re not sure how to sort that, just let me know what version of windows you run, and your router make & model, and I`ll help you out. If you don`t want to post your equipment in here, just PM me.
Cheers.