What the hell is 123.123.123 for an ip?
Your IP is 4 parts long and you need to give the guys who want to join
your internet ip. You can get it if you google “what is my ip” and check the
first site.
If still no one can enter, than i guess you need to forward the port in your router
settings and maybe allow the game to have connection through your Firewall.
Have you tried building the game and launching 2 copies of the game on one computer?
Do this first and try joining the IP 127.0.0.1
This is the localhost ( your own computer ). If this works, than the port is the problem.