Alright, so I have this problem with my port forwarded server where some of my friends can join, but the server has to be empty.
If the server isn't empty, they connect, walk around for 3 seconds and time out.
But that's only one of the problems.
I also have a problem where the ping is super high for my friends on the server.
By the way: It doesn't have anything to do with my WiFi because my brother can host his server just fine, but still has the time out problem.