To resolve the issue of players not being able to join custom games in Warcraft 3 while being able to join Starcraft games, it is essential to forward specific ports required by Warcraft 3. The necessary ports include TCP and UDP ports 6112-6119, as well as TCP ports 116 and 118. Additionally, adjustments to the firewall settings may be needed to allow traffic through these ports. For those at a university, direct access to network settings may be restricted, making port forwarding challenging. Using tools like Putty for SSH tunneling can be a workaround for routing traffic. Alternatively, a LAN emulator such as Hamachi can facilitate multiplayer gaming across different college networks by creating a virtual LAN. Resources like portforward.com provide detailed instructions for port forwarding based on specific modem models, which can aid in setting up the necessary configurations.