Port 21 — FTP Control

Q: Transport ProtocolTCPSafety precautionsOld and unencrypted service.Remain strongly or replace with the existing one.Should we open this port in the Burt?

Only if a service is actually needed l, use it. Apply the principle of any privilege: limit the authorized sources, destinations and interfaces, and then log connections when relevant.

Q: How do I check this port?

Test-NetConnection SERVER -Port 21Under Linux, you can use nc -vz SERVER 21.

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Port21

TransportTCP

ServiceFTP Control

Port 21TCP

FTP control channel.

What’s Port 21 for?

File transfer. The protocol or service generally associated is FTP Control.

Transport Protocol

TCP

Safety precautions

Old and unencrypted service.Remain strongly or replace with the existing one.

Should we open this port in the firewall?

Only if a service is actually needed the use it. Apply the principle of any privilege: limit the authorized sources, destinations and interfaces, and then log connections when relevant.

How do I check this port?

Test-NetConnection SERVER -Port 21

Under Linux, you can use nc -vz SERVER 21.

Port/service associations are common conventions. An application can be configured on another port.