IPv6 is a good multiplayer alternative for occasional play when blocked by CG-NAT

[Jim-Bar]

Hi everyone,

I just wanted to share this way of playing with friends when your Internet provider locks you behind a CG-NAT. I resorted to this for occasional playing, because I did not want to pay for a dedicated server. As a reminder, a CG-NAT prevents you from doing port forwarding on your router, effectively disabling the possibility for other players to join your game.

But if you are lucky enough to live in a country where IPv6 is streamlined, and you and all your friends have a public IPv6 address, this should work.

Pros:

• Relatively simple to set up
• Free
• No registration or third-party software required

Cons:

• In its simplest form, the setup must be done again for each new playing session
• Requires working IPv6
• The server runs on your computer, so is available only when you (the host) are playing (or when you launched Vintage Story's dedicated server on your machine)

Steps:

• Get your computer's IPv6 address (just type "my ip" on your favorite search engine)
• Open your router administration (most often found on 192.168.1.1, at least in my country) then set up a new port forwarding rule (for IPv6):
  • Protocol: TCP
  • External port: 42420
  • Internal port: 42420
  • External IP address: all
  • Internal IP address: your computer's IP address
• Start Vintage Story
• Start your single-player game
• Press ESC then "Open to LAN"
• Use a tool such as this one to check that friends can join your game (put your IPv6 address and 42420)
• If the tool reports that the port is open, friends will be able to join. They must enter the IPv6 and port like this in Vintage Story (replace by your IPv6, keeping the brackets): 

  [2a02:8428:80d6:d901:7010:e2df:557e:4e4a]:42420

Unfortunately your computer's IPv6 address changes after reboot / sleep / etc... You will have to redo the port forwarding step on your router each time. If you're a tech savvy you may find a way to use DynDNS or some other way to get a permanent solution, but that's out of the scope of this tutorial (read: I don't know how to do it).