Yay! My chance to help! Before anyone else...MUWAHAHAHAHAHAH!

Playing online is easier than finishing the JJ2 singleplayer episodes:
1. Start the game, then select new game.
2. Select Party Mode.
3. Select Internet Play.
4. Choose between joining a game and hosting a game.
5. Everything else should be total no brainers.

If that doesn't work then....
1. First make sure that you have either version 1.23 or 1.24 (I recommend 1.23, because there are more players on that version). If you got 1.24, you just got it, there's no patch for it. However, you can upgraded any non-1.24 version of JJ2 to 1.23 with this patch (run this patch before doing anything else): http://www.jazz2online.com/patches/j2patch_123r.exe

2. You will now need a listserver patch, so your JJ2 can connect to the, er, what's it called, 'master server'. If you got Macintosh JJ2, you'll need this: http://www.jazz2online.com/J2Ov2/med...verpatcher.sit and the Windows version is available here: http://www.jazz2online.com/serverlist/serverpatch.zip

3. Configuring your gateway settings is a bit complicated, and you may not even need to do it. http://www.jazz2online.com/J2Ov2/nod...rversHelpGuide should provide everything you need to know, but basically, you have to forward 10052 UDP to join games and 10052 TCP to host games. If you have a firewall, you may need to forward ports 10053 and 10054 too. I've told you what you need to do, but not how to do it (because all I know is what to do :/), so you may have to find out some things about your gatewaty by yourself.

4. A firewall may be the problem if you have tried, but failed, to play online. I don't know what firewall you're using, but generally, just tell your firewall to make an exception for JJ2, and it should no longer be blocking the connection.