I'm not too knowledgable about this type of thing, so bear with me.

A group of friends and I attempted to play a game online. I set up the server, and the other players needed my IP address to connect to me. When they tried, they failed. I tried disabling my firewall temporarily, and it still failed. A friend tried to create a server instead, and nobody could connect to him, and after trying to create on every person's computer, all we had were failures.

It's not just this one game. I have never successfully got a game that connects in this way to work. How can I do it?

Hmmm. That's a little vague on the configuration information, but many people these days connect to the internet through a router so that they can share their connection with several people. What this does is give your computer a private IP address that cannot be propagated on the internet, and then the router handles the translation. So, this doesn't work very well when you want others to connect directly to your computer.

Typically the private IP addresses are of the form 192.168.X.X, so if all the IP addresses you tried were of this form, that's the reason for the failure.

One other reason is as you mentioned: Firewalls can disallow traffic on the ports the game wants to use.

If it's neither of the above then I don't know, but perhaps someone who has actually done it and got it to work could help.

Try going to this site and give out these IP addresses to your friends instead.

http://checkip.dyndns.org/

Or search "ip address" on google and use any of those sites. They should all give you the same thing.

One thing you should also check is if you all have the same version. You should all install the same patches and add-ons or else it won't work.