Ok, I'll try to explain it again...
Let's see two common ways of connecting to the internet.
1) you have a PC, the PC is connected to a router and then the router is connected to a modem which provides internet.
2) you have a PC and the PC is connected to the modem without the need of a router.
Well.. in connection number 1 if you create a game nobody else can see it (but you still can join created games by others), and in connection number 2 everybody can see it and therefore join in your game.
I have connection number 1, but if I want others to play in any game created by me I have to change my connection to number 2 by unplugging and replugging to the new configuration. That's why I was wondering if there can be any fix to that, because this bug was since I begin playing Freespace 1 and 2 a long time ago when Paralax Online was still up and running.
(NOTE: the router doesn't have any block in any port)