Question: Which connection is opened during the entire session in FTP?

Answer:

During an FTP (File Transfer Protocol) session, two connections are opened:

1. Control Connection: This connection is established between the FTP client and the FTP server. It is used for sending commands, such as login credentials, directory navigation, and transfer requests. The control connection remains open throughout the session to facilitate communication between the client and the server.

2. Data Connection: The data connection is separate from the control connection and is used for the actual transfer of data (files) between the client and the server. The data connection is opened and closed for each file transfer. There are two modes of data transfer in FTP:

a. Active Mode: In active mode, the FTP server initiates the data connection to the client. The client listens on a specific port for incoming data connections. When the server needs to send data, it connects to the client's IP address and port, establishing the data connection.

b. Passive Mode: In passive mode, the client initiates the data connection to the server. The server listens on a specific port range for incoming data connections. When the client needs to receive data, it connects to the server's IP address and port, establishing the data connection.

In summary, the control connection remains open throughout the FTP session, while the data connection is opened and closed for each file transfer, depending on the mode (active or passive) being used.