I've recently installed Debian 10 in order to have a lightweight OS for hosting a java Minecraft server. But even after port forwarding to the computer's IPV4 address no external player can join the server, with an inputting external IP address.
However, players in the local network can join by directly entering the IPV4 address (the same one used to port forward). I'm fairly certain this isn't an issue with port forwarding, as I've already successfully port forwarded to a minecraft server hosted on a windows computer.
I've also tried installing UFW and disabling it entirely or simply allowing the 25565 port. If I understand correctly, UFW is a way to manage the firewall, and installing it doesn't add extra protection. But it seems as though it has no effect with disabling the computer's firewall.
How can I disable Debian's protection to allow external players to join my server?
You first need to install ufw, "sudo apt-get install ufw"
To show the status of the firewall, "sudo ufw status"
To disable the firewall, "sudo ufw disable"
To enable the firewall, "sudo ufw enable"