How do other people play your game?

[Reguba]

Sadly i have been stuck on this problem for days i know how to host a server and work everything else but when i got one of my friends the client to see if he could play my game i set all the configuration to what they needed to be but….the thing never said server on-line or anything...I'm just plain baffled! If you can help i would greatly appreciate it  ;D