FTP Server Project

Overview

This project implements a simple FTP (File Transfer Protocol) server in C. The server supports basic FTP commands for file transfer, directory listing, and user authentication. It is designed to provide a foundation for understanding the FTP protocol and socket programming.

Features

Implemented Features

• User Authentication:
  • Supports both default user credentials (USER and PASS) and anonymous login (anon).
  • Responds with appropriate error messages for invalid credentials.
• Directory Listing:
  • Handles the LIST command to send formatted directory listings over the data connection.
  • Displays file metadata such as permissions, size, modification time, and filename.
• File Transfer:
  • Implements the RETR (retrieve/download) command for downloading files from the server.
  • Implements the STOR (store/upload) command for uploading files to the server.
  • Supports both binary (TYPE I) and ASCII (TYPE A) transfer modes.
• Active Mode:
  • Handles the PORT command to establish data connections in active mode.
• System Information:
  • Responds to the SYST command with system type information (e.g., UNIX Type: L8).
• Graceful Shutdown:
  • Handles SIGINT signals to close the server gracefully.
• Error Handling:
  • Provides meaningful error responses for unsupported commands, syntax errors, and permission issues.

Future Features (Planned)

• Passive Mode:
  • Implement the PASV command to allow clients to connect to the server for data transfers.
• Concurrency:
  • Support multiple simultaneous client connections using threads or multiplexing (e.g., select() or poll()).
• Security Enhancements:
  • Add support for FTPS (FTP over SSL/TLS) to secure data transfers.
• Advanced Commands:
  • Implement additional FTP commands such as CWD (change directory), PWD (print working directory), DELE (delete file), MKD (make directory), and RMD (remove directory).
• Logging:
  • Add logging functionality to record server activity for debugging and auditing purposes.

Technical Details

Supported FTP Commands

• USER <username>: Authenticate the user.
• PASS <password>: Provide the password for authentication.
• QUIT: Terminate the session.
• PORT h1,h2,h3,h4,p1,p2: Specify the client's IP and port for active mode.
• LIST: Retrieve a directory listing.
• RETR <filename>: Download a file from the server.
• STOR <filename>: Upload a file to the server.
• SYST: Retrieve system information.
• TYPE <type>: Set the transfer mode (I for binary, A for ASCII).

Implementation Details

• Socket Programming:
  • Uses socket(), bind(), listen(), and accept() for the control connection.
  • Establishes a separate data connection for file transfers and directory listings.
• File Operations:
  • Uses standard file I/O functions (fopen(), fread(), fwrite()) for file handling.
• Error Handling:
  • Validates inputs and responds with appropriate FTP status codes (e.g., 500, 550).
• Platform:
  • Designed for Unix-like systems (Linux, macOS). May require adjustments for Windows compatibility.

Installation and Usage

Prerequisites

• A Unix-like operating system (Linux or macOS).
• GCC compiler installed.
• Basic knowledge of FTP and socket programming.

Build Instructions

Clone the repository:

git clone https://github.com/your-repo/ftp-server.git
cd ftp-server

Compile the server:

gcc -o ftp_server ftp_server.c

Run the server:

./ftp_server <port>

Testing the Server

Use an FTP client like ftp, lftp, or FileZilla to connect to the server:

ftp localhost <port>

Example commands:

USER user
PASS pass
LIST
RETR test.txt
STOR newfile.txt
QUIT

Future Work

The following features are planned for future releases:

• Passive Mode:
  • Allow clients behind firewalls or NATs to initiate data connections.
• Concurrency:
  • Support multiple clients simultaneously using threads or non-blocking I/O.
• Security:
  • Implement FTPS (FTP over SSL/TLS) for encrypted communication.
• Advanced Commands:
  • Add support for additional FTP commands like CWD, PWD, DELE, MKD, and RMD.
• Logging:
  • Log server activity to a file for monitoring and debugging.