File Transfer Protocol (FTP)

The File Transfer Protocol (FTP) is a standard network protocol used for the transfer of computer files between a client and server on a computer network. FTP is built on top of the TCP/IP protocol. It uses separate control and data connections. By default, FTP uses TCP port 21 for the control connection and typically port 20 for the data connection (active mode).

Overview

FTP was designed for efficient file transfer over networks. It supports commands for listing directories, changing directories, uploading, and downloading files. FTP is a stateful protocol, meaning the server maintains information about the client's session.

Key Features

• File Transfer: Supports uploading and downloading files.
• Directory Management: Allows clients to navigate and manage remote directories.
• Two Connections: Uses a control connection for commands and a data connection for file transfers.
• Authentication: Supports username and password authentication. Anonymous FTP allows access without credentials.

FTP Modes

FTP operates in two main modes:

• Active Mode: The client initiates the control connection and the server initiates the data connection back to a specified port on the client. This can be problematic with firewalls on the client side.
• Passive Mode: The client initiates both the control and data connections to the server. The server tells the client which port to connect to for the data transfer. This is generally more firewall-friendly.

Common FTP Commands

Here are some of the most common FTP commands:

USER <username>      - Specifies the username for authentication.
PASS <password>      - Specifies the password for authentication.
QUIT                 - Terminates the FTP session.
LIST                 - Lists the contents of the current directory.
CWD <directory>    - Changes the current working directory on the server.
PWD                  - Prints the current working directory.
RETR <filename>    - Retrieves (downloads) a file from the server.
STOR <filename>    - Stores (uploads) a file to the server.
PORT <host-port>     - Specifies the data connection port (for active mode).
PASV                 - Requests the server to enter passive mode.
TYPE <mode>        - Sets the file transfer mode (e.g., ASCII, Binary).

FTP Security Considerations

Standard FTP transmits credentials (username and password) and data in plain text, making it vulnerable to eavesdropping. For secure file transfers, consider using:

• FTPS (FTP over SSL/TLS): Adds encryption to FTP control and data connections.
• SFTP (SSH File Transfer Protocol): A completely different protocol that runs over SSH, providing robust encryption and authentication.

Windows Implementation

Windows operating systems include built-in support for FTP clients and servers. You can use the command-line ftp.exe utility or configure the Internet Information Services (IIS) to host an FTP server.

Using the FTP Client in Windows

To connect to an FTP server using the command line:

1. Open Command Prompt.
2. Type ftp <hostname_or_ip_address> and press Enter.
3. Enter your username and password when prompted.

Configuring an FTP Server on Windows

FTP server functionality can be added via the "Turn Windows features on or off" dialog, under "Internet Information Services" -> "FTP Server".

This documentation provides a foundational understanding of the FTP protocol within the context of Windows networking. For advanced configurations and security best practices, please refer to the detailed guides available within the full MSDN library.