yep it's a network problem
I'll try to explain...
some one who want connect your computer must have your ip adress
but the IP of your computer is not the same as the router one
if someone want to connect you he enter the ip of your router
he connect to your router but no server on the router the server is on your computeur
so you have to tell to your internet box that you want to redirect computer who connect to her to your pc.
for the rest :s on my computer you have to go in NAT-SETTING
but all box are not the same :s
if you are on windows you can have the ip adress of your computer execute=>cmd=>ipconfig
here the config of mine
hope that is helpfull