Process of Setting Up an FTP Connection

 

The process of setting up an FTP data connection by using active mode is as follows:

1. The server enables port 21 to wait for a connection request from the client.

2. The client sends a connection request to the server.

3. After the request is received, a control connection is set up between the temporary port on

the client and port 21 on the server.

4. The client sends a command for setting up a data connection to the server.

5. The client chooses a temporary port for the data connection and sends the port number by

using the port command to the server over the control connection.

6. The server sends a request to the client for setting up a data connection to the temporary

port on the client.

7. After the request is received by the client, the data connection between the temporary port

on the client and port 20 on the server is set up.

The process of setting up an FTP data connection by using passive mode is as follows:

1. The server enables port 21 to wait for a connection request from the client.

2. The client sends a connection request to the server.

3. After the request is received, a control connection is set up between the temporary port on

the client and port 21 on the server.

4. The client sends a command for setting up a data connection to the server.

5. The client sends a command string PASV to the server to request the port number.

6. The server chooses a temporary port for the data connection and sends the port number to

the client over the control connection.

7. The server sends a request to the client for setting up a data connection.

8. The data connection between the temporary port on the client and the temporary port for

the data connection on the server is set up.

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