If they are on the same router, then what I was saying applies. Port forwarding or the
DMZ host option is not necessary as that simply routes incoming packets from the WAN. Are you sure the host's IP address is correct? On that computer open command prompt and type
netstat, it'll tell you the computer's IP. Addresses on a local area network will change sometimes unless the machines specifically request a static IP from the router.
If you are typing the host's IP correct and you are still having trouble, it's most likely a firewall problem. Disable the firewalls on both machines and try again.
If still no luck, try pinging one machine from the other in command prompt. If not successful, then you have a problem.
Quote: "But then again I've tried connecting to 100.100.100.100 and it did the same thing"
Where did that address come from?
If you don't mind, could you perhaps upload an extremely simple game made with v1.5 so that I can test it on my network? I would do, except I don't have FPSC. I did have a v1.4 game working, but there might be something broken in the latest version.