Updated: 28 September 2026 · Applies to: Ubuntu 24.04, Debian 12, AlmaLinux 9 and Rocky Linux 9
CentOS 6 and 7 are end of life. These are the current ways to open and close a port (5555/tcp in the examples).
AlmaLinux / Rocky Linux (firewalld)
firewall-cmd --permanent --add-port=5555/tcp # open firewall-cmd --permanent --remove-port=5555/tcp # close firewall-cmd --reload firewall-cmd --list-ports
Ubuntu / Debian (UFW)
ufw allow 5555/tcp # open ufw delete allow 5555/tcp # close ufw status
Check that the port is open
- On the server, check that a program listens on the port:
ss -tlnp | grep 5555. If nothing listens, the port looks closed even with the firewall open. - From another computer, test it:
nc -zv SERVER-IP 5555.
Note: On cPanel servers the firewall is usually managed with the firewall tool installed in WHM; open ports there instead of with firewall-cmd.
Tip: On a Ucartz VPS, keep the VNC console open (client area › your VPS service › VPS dashboard) while you change firewall or network settings. If you lock yourself out of SSH, you can still fix it from the console.
