Wow, this is from SIF and posted by lenvda which has just been stickied:
Lightbulb Sacred2 and Hamachi works! (confirmed)
1. Install Sacred2, and update it to the latest version.
2. Install Hamachi, join or create a new network and have your friends do the same.
3. Add "hamachi.exe", "sacred2.exe" and "s2gs.exe" to the exception list in your firewall.
4. If you have a router, open port 7011 (default port when hosting Sacred2 multiplayer game).
5. Open Hamachi and