lookup> port 21

21 ·Port

File Transfer Protocol [Control] (tcp/udp).

tcpudpftp
Status21
Serviceftp
Protocoltcp / udp
Well-knownYes (0–1023)

What runs on port 21?

File Transfer Protocol [Control] (tcp/udp).

Well-known ports are assigned by IANA to system-level services; binding them usually requires administrative privileges.

FTP control channel. Plain FTP sends credentials in clear text; prefer SFTP or FTPS.

RangeExplanation
Well-known (0–1023)Reserved for system services; binding usually requires admin privileges.
Registered (1024–49151)Available to user applications; IANA registers common services here.
Dynamic / private (49152–65535)Used for ephemeral client connections.

Is port 21 TCP or UDP?

A port number is a transport-layer address used independently by TCP and UDP; ftp typically runs over its documented transport protocol.

Can I change what runs on port 21?

Yes — most services let you configure the listening port, but make sure clients and firewalls are updated and you avoid conflicts.

Related ports

Common services

Related headers

Related status codes