Already done that. You're not really correct when you say "All dumb here."All dumb here.
Leave server-ip blank in the server.properties.
Then portforward the port u want to use.
Then get your public ip from here: www.whatsmyip.org
Then tell your friends to connect to "yourpublicIP:theport" if u use default port "25565" then they only need to connect to the public ip.