Port 21

Q: What is port 21?

FTP control channel for commands and responses Port 21 is the FTP control channel through which the client sends commands (login, LIST, RETR, STOR) and receives server responses. Actual file data flows through port 20 in active mode or a negotiated ephemeral port in passive mode. FTP is a legacy protocol with no encryption — credentials and data are transmitted as plaintext. Modern deployments replace it with SFTP (over SSH) or FTPS (FTP over TLS). Many firewalls block inbound port 21 from the public internet.

FTP

FTP control channel for commands and responses

Port

Protocol

TCP

Service

FTP

Security

Restricted

Full name: File Transfer Protocol – Control

What is port 21?

Port 21 is the FTP control channel through which the client sends commands (login, LIST, RETR, STOR) and receives server responses. Actual file data flows through port 20 in active mode or a negotiated ephemeral port in passive mode. FTP is a legacy protocol with no encryption — credentials and data are transmitted as plaintext. Modern deployments replace it with SFTP (over SSH) or FTPS (FTP over TLS). Many firewalls block inbound port 21 from the public internet.

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