A portforward from the router to the local LAN address of the computer who have the minecraft server and also you need to make sure that the computer doesn't get a new IP from the router's DHCP so the portforward rule will not break.
A portforward from the router to the local LAN address of the computer who have the minecraft server and also you need to make sure that the computer doesn't get a new IP from the router's DHCP so the portforward rule will not break.