Craftopia Solution for Can Not Use Multiplayer/ Server Time Out

open a browser
on the address bar enter this ip address (default router page): 192.168.1.1
find your port forwarding/port options and open the port that you are using for hosting the game.(this might be different for every router look up instructions online for your specific router but it goes something like this)ports/port forwarding > add rule >
port 8787,
connection type tcp/udp,
forward to: select your pc (server) ip address
apply changes and done!

you can read more about opening ports here:
https://www.computerhope.com/issues/ch001201.htm

There is another guide that says to setup a vpn as a workaround here’s why that might work:
when you connect to the vpn it makes you part of the vpn’s local network that is to say all your internet trafic is now going throught the vpn hosts router. Because you two are using the same router you can essentially join their server through a LAN (local area network) party. This solution is fine and all if you dont want anyone else to try to connect to your server (because anyone with your ip can connect if you are using the default port) but then your friends need to connect to your vpn and all that.

ps: If this doesn’t work check your pc firewall