Port 21 — FTP
Quick reference for TCP/UDP port 21, used by FTP. Includes what the service does, security guidance and related ports.
What is port 21?
File Transfer Protocol control channel.
What port does FTP use?
FTP listens on port 21 by default.
Is port 21 open? How to check
Run one of these from your computer, replacing HOST with the IP address or domain you want to test.
nc -zv HOST 21
Test-NetConnection HOST -Port 21
nmap -p 21 HOST
A refused or timed-out connection means the port is closed or filtered by a firewall.
Security guidance
High risk — do not expose to the internet
Port 21 (FTP) is high-risk because the service it carries is a frequent target for credential attacks, brute force or unpatched-vulnerability scanning. Keep it bound to localhost or your VPN, never forward it directly on a router, and require strong authentication.
Devices that use port 21
4 devices in our database expose a service on port 21.
Related ports
Frequently asked
What is port 21 used for?+
Port 21 is the standard TCP/UDP port for FTP. File Transfer Protocol control channel.
What port does FTP use?+
FTP listens on port 21 by default.
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