First of all, if you're using a router (which most people are), you need to forward the port (6121) that OINC uses.
1. Go into start > search for CMD > type ipconfig and press enter.
Now you should see your IP configs for your router. (It's the one saying standard gateway).
Now use that IP and put it into your browser. Now logon to your router (you should know the pass and username). When you have logged on, simply go to applications and games. You shold see something called Port Range Forward or something like that.
Now theres list with all kinds of stuff.
The first one will say Application name
The second one is the first port
The third one is the last port
The fourth one is Protocol
The fifth one is IP adress
And number six option is Enable
Now. You will need some information.
1.In the first one just write OINC so you can remember why you did it.
2.The ports we want to forward is the port that OINC uses (6121), so in the second and third one write 6121.
3.In the fourth option you will choose BOTH because we need both UDP and TCP.
4. Write the IP adress you have been givin' in the CMD IPv4-adress. Check CMD again.
5. Click enable!
6. Your done and click Save settings
Now you have forwarded the port. You can now use it to host servers for other ppl to join. They will have to connect to your IP adress to connect. You can find your IP adress at: http://www.whatismyipaddress.com/