Originally posted by Takama:

You should definitely be able to join your own server by using your ip and port, especially if it works for your friends. I'm guessing your issue is then your own firewall on your pc, that may be blocking the access.

As for the server browsing, it may be the case that you forgot to forward port+1, I think this one is the one used for listing the server.

Finally, if the server is on the same computer you're playing on, just join using localhost : 127.0.0.1:PORT

That did the trick! I was using the external IP to try and connect, not my internal IP! Thanks so much!