I've been at this for most of the day. I can get any version of vanilla Minecraft server installed, currently 1.12.2, but I cannot connect to it; it acts as if it's just offline.
-I'm on a VPS with CentOS 6.9 installed.
-Appears to run fine when executing the following via SSH as root or user: "screen java -Xmx1024M -Xms1024M -jar minecraft_server.jar nogui"
-iptables has 25565 at the top of the INPUT chain, port is verified open and java is listening on it.
-SELinux is disabled.
-server.properties has no ip listed (inputting ip doesn't make a difference) and port as 25565. Only other changes made from default were motd and world name.
-eula.txt has "eula=true"
I was gonna suggest you look at the OUTPUT chain, but default iptables rules for CentOS has it accept all and you mention the "port is verified open" (so I guess that means the 3-way handshake is being executed).
Another place to look is the log files, /var/log/, and in particular, /var/log/messages. I doubt anything will show up there though, since SELinux is disabled and the port is open. Still worth a look.
So you're not getting a connection timeout or a connection refused then?
TCPDUMP shows the in/out of the port checker, but not the server checker. It also shows the minecraft app attempting to connect on UDP port 25565, which the port checker says is closed, even though I have it in my iptables as the first line in both INPUT and OUTPUT chains.
If I stop the iptables service entirely, all ports should then be open, correct? UDP 25565 is still closed. I'm suspecting this is my issue, not sure how to fix it.
My Minecraft client (WIndows 10 App) says "Connecting to external server" followed by "Unable to connect to world".
So "Closed" port means that it's responding to packets but no applications are listening on that port.
It appears the server is not listening on UDP. Is it supposed to? If so, how to fix it?