Understanding FTP: A Complete Guide to File Transfer Protocol and Its Uses

FTP, or File Transfer Protocol, is an application layer protocol used to exchange files between computers over the internet. It allows users to upload and download files to and from websites. If you’ve ever downloaded a file from the internet, you’ve likely used FTP. 

FTP operates on a client-server model architecture. For a client to receive a file from the server, it must have the appropriate permissions. However, some FTP servers allow access without requiring credentials, known as anonymous FTP. 

How It Works? 

FTP establishes two connections between the local and remote hosts: one for control and one for data transmission. 

• Control Connection: This is the first connection established between the client and server. It is responsible for managing the communication between the two, allowing the client to send and receive commands from the server. 

• Data Connection: This second connection is responsible for the actual file transfer. After the client sends a command to retrieve a file through the control connection, the file is transferred over the data connection. 

The default ports for FTP are port 21 for the control connection and port 20 for the data connection. However, these ports can be changed based on your needs, such as when running multiple servers on the same machine and wanting to avoid port conflicts. 

FTP Flow 

1. To connect to an FTP server, the client first requests the server’s IP address and port number. The server responds with a confirmation, indicating that the connection has been successfully established.

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2. The client then signs into the server by providing a username and password. If the login details are correct, the server grants access. In some scenarios, the server might allow anonymous access without requiring credentials.

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3. After successfully logging in, the client can perform various FTP commands, such as uploading, downloading, deleting, or listing files on the server. 

4. For file transfers, the client sets up a separate data connection with the server. This connection handles the actual transfer of files between the client and server. 

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5. Once the file transfer is complete, the data connection is closed. The client can then continue issuing additional FTP commands or disconnect from the server. 

How To Transfer Files Using FTP? 

We’ve learned how FTP works, but now you’re probably wondering how to actually transfer files from one computer to another using FTP. There are several ways to do this, each depending on the tools you prefer or the task at hand: 

1. Command Line (CMD)