P2P File Exchange

Simple peer-to-peer file sharing for your local network. Run it on two devices on the same Wi‑Fi/LAN, it finds other peers automatically, and can send files through a cross‑platform desktop app.

Warning

This app is not audited for security. Do not use it to transfer sensitive files over untrusted networks.

Features

• Automatic peer discovery on the local network via UDP broadcast
• Ed25519-signed discovery to prevent peer impersonation
• End-to-end encrypted transfers with X25519 + ChaCha20-Poly1305
• TOFU (Trust-On-First-Use) identity verification with persistent trust database
• Per-chunk SHA-256 integrity validation
• Drag-and-drop or file picker sending
• Transfer progress, speed, and ETA tracking
• Automatic download folder and collision-safe file naming

Screenshots

Note

Peer discovery uses UDP broadcast, so devices must be on the same LAN.

Requirements

• .NET SDK 10.0

Quick Start

dotnet restore
dotnet run --project src/P2PFileExchange.Desktop

Run the app on two machines on the same network, start discovery, and send files between peers.

Default Download Location

Inbound files are saved to:

~/Downloads/P2PFileExchange    (Linux)
%USERPROFILE%\Downloads\P2PFileExchange    (Windows)

Network Details

Protocol	Port	Purpose
UDP	37020	Peer discovery broadcasts
TCP	Dynamic	File transfers (port announced via discovery)

Note

If discovery or transfers do not work, ensure UDP broadcast and TCP traffic are allowed by your firewall.

Documentation

For detailed specifications, see:

Document	Description
Security Architecture	Cryptographic design, threat model, trust database
Peer Discovery Protocol	UDP broadcast, signed announcements, verification
File Transfer Protocol	TCP transport, chunking, integrity checks

Building

# Restore dependencies
dotnet restore

# Build release
dotnet build -c Release

# Run tests (if any)
dotnet test

License

This project is licensed under the MIT License - refer to LICENSE file for details.