Port 20
ftp-data · SCTP/TCP/UDP
| Range | System/well-known port (0–1023) |
|---|---|
| Protocol | SCTP/TCP/UDP |
| Service | ftp-data |
| Reference | RFC 9260 |
| Modified | 2022-02-07 |
Frequently asked questions
What is port 20 used for?
Port 20 is registered with the IANA for ftp-data (SCTP/TCP/UDP). Description: File Transfer [Default Data]; FTP.
Is port 20 a well-known port?
Yes. Port 20 is in the range 0–1023 (system or well-known ports). On Linux and macOS only privileged processes may bind to these ports.
How do I check whether port 20 is open?
Locally on Linux with ss -tulpn | grep ':20\b', on Windows with netstat -ano | findstr :20. To test a remote host use Test-NetConnection <host> -Port 20 in PowerShell or nc -zv <host> 20 on Linux/macOS.
How do I open port 20 in the firewall?
Ubuntu/Debian (ufw): sudo ufw allow 20/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=20/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 20" -Direction Inbound -Protocol TCP -LocalPort 20 -Action Allow.
IANA registry entries
| Protocol | Service | Description (IANA) |
|---|---|---|
| TCP | ftp-data | File Transfer [Default Data] |
| UDP | ftp-data | File Transfer [Default Data] |
| SCTP | ftp-data | FTP |