My girlfriend bought a copy last night to play with me, and I've been trying to get a server working between us.
This game is just too frustrating to play multiplayer right now.
If you don't plan on it being a public server forget the usage of hamachi.
1. Just go to your installation folder (default: C:\Program Files (x86)\Cube World), then run server.exe
2. It should start up and the ending line will say "Waiting for connection"
3. Exit server.exe and check your cube world folder now for something named server.cfg
4. Open it and it contains the world seed for the world you are now running, change this if you want
5. Now re-run server.exe
6. Find your external IP address and give it to whoever needs to connect, they use "Connect to server" located on the bottom right corner after they choose their char
7. If they cannot join, forward port 12345 both UDP and TCP and retry