Port 20 — FTP data

Security guidance

FTP sends everything, credentials included, in clear text. Use SFTP on port 22 instead.

Test port 20 yourself

From your own machine, against any host (swap in your domain):

macOS / Linux — netcat

nc -vz example.com 20

Any OS — nmap

nmap -p 20 example.com

Windows — PowerShell

Test-NetConnection example.com -Port 20

open = a service answered on port 20; closed = the host replied but nothing is listening; filtered = a firewall silently dropped the probe. These test from your network — our port checker tests from the outside, the view that matters for security.

Other common ports