Help: Setting up, running, and maintaining a server

[Minix]

If it works inside a LAN then your server is ok. Now if you want it to work over the internet you have to forward the port that your minetest server listens to (by default is 30000), to your server (your computer). Look up the name of your router + port forwarding on the internet.

Then you have to give your friends your internet IP address, which you can see on your router or on an IP address detection website.