Running multiplayer over the internet. Is it possible without using Hamachi?

[6741c8ad1a7a5mcduke]

I have acouple of friends who are interested in playing system shock 2 with me  but, they don't want to load Hamachi on their systems ( they're a rather paranoid lot and don't trust it I guess, afraid that it will cause problems with their computers somehow and they don't think it's secure). So, is there a way to run system shock 2 in multiplayer mode over the internet?  I tried setting up the server and even did dmz in the router ( I still had zone alarm up) but, the connection failed. Then I also turned off zone alarm (just to see if it would connect then) and my friend got the connecting notice that lasted forever, but I never saw his name appear as a player. All of us run out systems through routers. Is it possible to run the server without Hamachi, and if it is then how?

[6741c8ad1aa47Kolya]

Basically yes. It's possible to play without Hamachi.
But I've tried myself for hours configuring a game through a router (and it didn't work).
All I can say is: Use the router settings as described here.
And look for further advice here.