Port 20 (TCP) — FTP data

FTP active-mode data transfer.

🔒 Runs locally — your input never leaves this browser tab

FTP sends credentials in clear text. Use SFTP (port 22) instead.

Check if port 20 is open

On the server, see what is listening:

sudo ss -tulpn | grep ':20 '

From another machine, test reachability:

nc -zv your-server.example.com 20

With UFW (Ubuntu/Debian):

sudo ufw deny 20

With firewalld (RHEL/AlmaLinux/Rocky):

sudo firewall-cmd --permanent --remove-port=20/tcp && sudo firewall-cmd --reload