FTP data connections use which port and protocol?

FTP data connections use which port and protocol?

• A. 21 TCP
• B. 20 TCP
• C. 23 TCP
• D. 67 UDP

Answer: (B)

FTP uses TCP and establishes two channels: a control channel on port 21 for commands and a data channel for transferring files. In the traditional active FTP setup, the data connection is created from the server’s port 20 to a port chosen by the client, so the data path uses TCP on port 20. That’s why port 20 TCP is the correct match for FTP data connections. The other ports don’t fit: port 21 is for the control channel, port 23 is used by Telnet, and port 67 is used by DHCP. Keep in mind that in passive mode the data connection uses a server‑chosen high port, but TCP remains the transport and the question points to the typical data port, which is 20.

FTP uses TCP and establishes two channels: a control channel on port 21 for commands and a data channel for transferring files. In the traditional active FTP setup, the data connection is created from the server’s port 20 to a port chosen by the client, so the data path uses TCP on port 20. That’s why port 20 TCP is the correct match for FTP data connections. The other ports don’t fit: port 21 is for the control channel, port 23 is used by Telnet, and port 67 is used by DHCP. Keep in mind that in passive mode the data connection uses a server‑chosen high port, but TCP remains the transport and the question points to the typical data port, which is 20.