I'm working on using a Google Compute Engine instance running CentOS 6.6 as a Minecraft server, and I'm curious if it is technically possible to use port forwarding to allow other users to access it. I've been working with it for a couple hours now, and I've created a Firewall rule opening tcp:25565 (the relevant port). When my friend tries to connect, I'm seeing his IP in the game console as part of a "connection lost" error message. The server has a static IP which he is using to try to connect. I am fully able to connect to the instance via SSH from my personal computer, which is how I've been interacting with it the entire time.
Java is updated to 1.8 on the instance, and the server is running smoothly, it's just a question of allowing other people to access it. Where do I go from here?