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What is P2P File Share?

P2P File Share is a pure peer-to-peer file sharing system built with Node.js, inspired by the BitTorrent protocol. It enables multiple clients to exchange files directly with each other without requiring a central server. Each node acts as both a client and a server, creating a distributed network where files are shared efficiently among peers. Unlike traditional file sharing systems that rely on centralized servers, P2P File Share implements a fully decentralized architecture where:
  • No central server is required - Files are transferred directly between peers
  • No tracker dependency - Peer discovery happens through peer exchange (PEX)
  • Equal participation - Every node can accept incoming connections and connect to known peers
  • Collaborative distribution - Files are divided into pieces that are downloaded and shared simultaneously, accelerating distribution
This is a prototype implementation designed for educational purposes. It does not include encryption or authentication mechanisms.

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Key Features

Pure P2P Architecture

No trackers or central servers required. Operates in a fully distributed manner.

Peer Exchange (PEX)

Dynamic peer discovery - nodes share information about other peers to build the network.

Piece-based Transfer

Files are divided into 64 KiB pieces (configurable) for efficient parallel downloading.

Integrity Verification

SHA-1 hash calculation and verification ensures file integrity after download.

Progress Tracking

Real-time console output showing download percentage, bytes transferred, and average speed.

Cross-platform

Works on Linux, Windows, and macOS with Node.js v22+.

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Architecture Overview

The P2P File Share system uses a mesh network topology where nodes connect to each other via TCP sockets. The protocol implements several message types for coordination:

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Protocol Messages

  • handshake - Initial connection and metadata exchange (file name, size, hash, piece size)
  • bitfield - Broadcast which pieces a peer currently has available
  • request - Request a specific piece from a peer
  • piece - Send requested piece data (base64 encoded)
  • have - Notify peers when a new piece is acquired
  • peers - Exchange peer addresses for network discovery

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How It Works

  1. Seeder nodes have the complete file and listen for connections
  2. Leecher nodes connect to a seed or another peer to begin downloading
  3. Nodes exchange metadata through handshake messages
  4. Peers share their piece availability via bitfield messages
  5. Leechers request pieces from peers that have them
  6. As pieces are downloaded, nodes notify others via have messages
  7. Once complete, leechers verify file integrity and become seeders themselves
The system implements an anti-collision rule: only the peer with the higher ID initiates connections to prevent duplicate connections between the same pair of peers.

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Project Structure

The codebase is organized into three main modules: 
p2p-file-share/
├── src/
│   ├── manager.js    # File I/O operations and hash calculation
│   ├── node.js       # P2P logic: connections, protocol, piece exchange
│   └── peer.js       # Entry point: argument parsing and node startup
├── package.json      # npm configuration and scripts
└── README.md         # Project documentation

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Module Responsibilities

  • manager.js - Handles reading and writing file pieces, calculating SHA-1 hashes
  • node.js - Core P2P networking, TCP connections, message protocol implementation
  • peer.js - Command-line interface and application entry point

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Use Cases

P2P File Share is ideal for:
  • Learning - Understanding how BitTorrent-style protocols work
  • Local networks - Fast file distribution across multiple machines
  • Development - Building custom P2P applications
  • Education - Teaching distributed systems concepts
This implementation does not include encryption or authentication. Do not use it to share sensitive files over untrusted networks.

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What’s Next?

Ready to get started? Follow the Installation guide to set up P2P File Share, then try the Quickstart tutorial to share your first file.

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