Hosting a Game

Been enjoyin the game quite a bit since I got her. But today when my friend got it we went online and I was going to host a server for us it told me that SDC found a firewall or router were stoppin people from joining and sure enough he couldn't get in. SO, I disabled the firewall for a period of time and nothing. Still wouldn't work. So then, I come to you asking how to fix this minor issue...or can I even? Yes, I do have a router hooked up.