Originally Posted by NoseyNick
Not clear exactly which "procedure laid out by LawsonThompson" you're referring to, but summarising from my own experience:
You'll run the server on one of your machines. The server screen will probably tell you its INTERNAL IP, likely 10.x.x.x, 192.168.x.x or 172.x.x.x?
You'll make sure any Windows/OS/3rd-party firewall on that server allows inbound TCP port 2010.
You can test from other machines on the same LAN, they should be able to connect and play? They will continue to connect to this INTERNAL IP.
On your router you'll configure a port-forward, to forward EXTERNAL TCP 2010 to INTERNAL [server address above] 2010
To complicate things: If you have any other routers "daisy-chained", you'll need to have done the above for the "most internal" one first, then find the EXTERNAL IP of that first router, and get the SECOND router to forward ITS external TCP 2010 to the first router's external 2010
Finally you'll need to know the external IP of your outer-most router (hopefully only one router?). Your router might tell you on a status page, BUT if it's another 10.x.x.x, 192.168.x.x or 172.x.x.x one it strongly implies there's another firewall somewhere beyond, like your ISP runs a big "carrier-grade firewall/NAT", where you probably can't configure port-forwards. Unfortunately this is fairly common, especially on Cable, less so but still happens on DSL.
If your (one and olny?) router doesn't tell you its external IP, good chance you can find this by browsing to https://icanhazip.com/
- and THIS is the address you'll share for other people over the internet to connect to (not the internal 10.x.x.x, 192.168.x.x or 172.x.x.x one).
Bear in mind you're assuming NONE OF THE ABOVE CHANGE. If your server machine has changed IP between tests (did you reboot / power-cycle something?) then you'll need to fix the port-forward. If your external icanhazip.com address has changed (Did you reboot the router, or go offline for some other reason?), you'll need to inform your internet players.
To reiterate: Your internal LAN players will still connect to the INTERNAL 10.x.x.x, 192.168.x.x or 172.x.x.x address. Your external / Internet players will connect to your external / icanhazip.com IP address via your port-forward(s).
If it still doesn't work, it's possible your ISP is filtering / firewalling inbound connections on a GCFW/CGN as above, in which case you're pretty much doomed I'm afraid.
Anyone who tells you you need UDP 2010, or any other ports, is misinformed, misled, lying, or trying to expose other services (do you wanna run TeamSpeak too for example?) or possibly even trying to hack you.
There's other UDP stuff happens on the LAN ONLY for the auto-discovery, but that ain't gonna work over the interwebs no matter how hard you try. TCP 2010 inbound is the only one that matters for Artemis.
Hope that helps!