COMPUTER NETWORKING

Detailed explanation-1: -The FTP protocol typically uses port 21 as its main means of communication. An FTP server will listen for client connections on port 21. FTP clients will then connect to the FTP server on port 21 and initiate a conversation.

Detailed explanation-2: -Port 21/TCP 21/TCP is used for the control channel – the client and server talk over this port and when the client is ready to upload or download a file or directory, the client and server discuss what port number they want to use for the data channel for this single transfer.

Detailed explanation-3: -FTP is a TCP based service exclusively. There is no UDP component to FTP. FTP is an unusual service in that it utilizes two ports, a ‘data’ port and a ‘command’ port (also known as the control port). Traditionally these are port 21 for the command port and port 20 for the data port.