This falls in the realm of setting up your router(s)/modem
port 80 is usually for http. you dont need to use that one specifically. in fact you should stay away from it
127.0.0.1 is a fake ip it's not your PC's IP, it a stub because it's easy to remember. It's like the "self" keyword in GML... Your actual IP can be found on the router, it resolves to your machine, it's akin to "id" for instance in GML... you get it? id and self point to the same instance in gml though (in 1.5) the values have different digits... 127.0.0.1 and the IP on the router act the same way.
look at the code for the game's server section, look at the ip : port it opens, 127.0.0.1:somethingnot80please
look at your router, see what IP your router says your pc really uses (as seen by others on the network or the internet)
change the code in the game's client section, look at the ip : port it opens, change the 127.0.0.1 part to the ip the router says. and the port to be the same.
run the server on your machine
run the client on your machine
client should connect. Since it's connecting locally
run the client on another pc in the house, the client should connect to your PC to the port the game server code has opened, I mean if it's allowed by the router.
Try from another machine that does not see your machine on your local network but only through the internet (a friend's machine or a machine not on the same network, meaning the only way they can see it is the long way around) if it's allowed in by the router the client should see your game server... if not you need to tweak you modem and any router in between the internet and the modem to allow external connections to happen. you would need to do this for outside ppl to see you web server too. This part you need to find a good port forwarding tutorial that matches your hardware (not a game maker one) on the internet.