Trying to fix this for kids, can't log on using other computers

[bearbin]

It sounds like he's managed to port forward fine. There's a few things I can recommend for now though -

• Don't run a server on a Mac unless you compile yourself, because the binaries are out of date.
  
• Make sure that the computer running the server does not change IP when the router is rebooted or the PC is rebooted - some routers have DHCP servers that change the IP, some not. If it changes, set up a static IP out of the dynamic range for the PC.
  
• Make sure any firewall software on the PC side is not blocking the port (bad antivirus apps, improperly configured firewall).