Hi Erniud
Re SH3 Multiplayer things have moved on since my Tunngle post due to new privacy laws Tunngle has shut down.
You can still play SH3 Multiplayer with Evolve Link Below
https://www.evolvehq.com
once you have downloaded Create a account gaming name Password then download client software if you have Windows 10 when you login it says your offline shut down evolve then go to your control panel system device manager
network adapters evolve will have a yellow triangle Error go to advanced in the mac address box enter 0 then click ok and the Yellow Triangle has gone and when you login to Evolve it says your online and when you make a lan party you see your green online button and your ip for that gaming session
When you invite your friend he will have a similar ip to you just one digit more eg your ip 169.108.44.134 his ip 169.108.44.135 happy game hosting
blackswan40