A very strange thing has happened to me.

If I start the server and try to login, everything's fine. Once I logout or close my client, then try to login again, it doesn't work at all, I would have to restart my server to be able to login correctly again. I have portforwarded it correctly and nothing's wrong there.
But anyways when I try to login with ip '127.0.0.1' it works everytime, but with the internet ip, that's when it happens.