- Plesk for Linux
- Plesk for Windows
Why FTP server needs port 20 to be opened?
Port 20 is used in active mode for FTP data transfer.
FTP server may run in active or passive mode, which determines how the data connection is established. In both cases, the client creates a TCP control connection from a random, usually an unprivileged, the FTP server command port is 21.
In active mode, the client starts listening for incoming data connections from the server on port M. It sends the FTP command PORT M to inform the server on which port it is listening. The server then initiates a data channel to the client from its data port 20, the FTP server data port.