BitTorrent Implementation

A peer-to-peer file sharing application implementing the BitTorrent protocol in C++.

Overview

This project is a simplified implementation of the BitTorrent protocol, featuring a tracker server for peer coordination and client applications for file sharing. It demonstrates core concepts of distributed file sharing including piece-based transfer, multi-peer downloading, and file integrity verification.

Project Structure

bit_torrent/
├── README.md                # Project overview (this file)
├── problem/                 # Problem statement and resources
│   └── links.txt           # Reference links
└── solution/               # Implementation code
    ├── README.md           # Detailed implementation documentation
    ├── tracker_info.txt    # Tracker configuration
    ├── client/             # Client implementation
    │   ├── client.cpp
    │   ├── peer_server.cpp
    │   ├── utility.h
    │   └── Makefile
    └── tracker/            # Tracker implementation
        ├── server.cpp
        ├── client_handle.cpp
        ├── utility.cpp
        ├── utility.h
        └── Makefile

Quick Start

Prerequisites

• C++ compiler (GCC/Clang) with C++11 support
• Make build tool
• POSIX Threads library
• OpenSSL library (for crypto functions)
• readline library

Installation

1. Clone the repository:

git clone https://github.com/viserion999/bit_torrent.git
cd bit_torrent/solution

2. Build the tracker:

cd tracker
make

3. Build the client:

cd ../client
make

Running

1. Start the tracker server:

cd tracker
./tracker ../tracker_info.txt 101

2. Start client(s) in separate terminals:

cd client
./client 127.0.0.1:6000 ../tracker_info.txt

Key Features

• Peer-to-Peer Architecture: Decentralized file sharing between clients
• Tracker Coordination: Central tracker maintains peer lists and file metadata
• Chunk-based Transfer: Files divided into 512KB chunks for efficient distribution
• Multi-peer Downloads: Download different pieces from multiple peers simultaneously
• File Integrity: Hash verification for each chunk to ensure data correctness
• User Authentication: Login/logout system for clients
• Group Management: Organize file sharing within groups
• Concurrent Connections: Multi-threaded architecture for handling multiple transfers

Architecture

Tracker Server

• Maintains database of users, groups, and shared files
• Tracks which peers have which file pieces
• Coordinates peer discovery and connection
• Handles user authentication and group management

Client/Peer

• Acts as both client (downloading) and server (uploading)
• Maintains local file storage and metadata
• Connects to tracker for peer discovery
• Establishes direct connections with peers for file transfer
• Verifies chunk integrity using hash verification

Usage

Client Commands

Once connected, clients can use these commands:

• create_user <user_id> <password> - Register a new user
• login <user_id> <password> - Login to the system
• create_group <group_id> - Create a new sharing group
• join_group <group_id> - Join an existing group
• leave_group <group_id> - Leave a group
• list_groups - Show all available groups
• share_file <file_path> <group_id> - Share a file with a group
• list_files <group_id> - Show files available in a group
• download_file <group_id> <file_name> <dest_path> - Download a file
• logout - Logout from the system
• quit - Exit the client