PeerLink

A simple peer-to-peer file sharing application that allows users to share files directly between devices using invite codes.

Overview

PeerLink consists of a Java backend server and a Next.js frontend that enables secure file sharing without storing files on external servers. Files are transferred directly between peers using dynamically generated port numbers as invite codes.

Features

• Direct peer-to-peer file transfer
• No external file storage required
• Invite code system for sharing files
• Support for multiple file types: .txt, .jpeg, .img, .pdf
• File size limit of 10 MB (recommended)
• Modern web interface with drag-and-drop functionality

Architecture

Backend (Java)

• HTTP server running on port 8080
• File upload and download endpoints
• Dynamic port allocation for peer connections
• Socket-based file transfer between peers
• Built with Maven and Java 17

Frontend (Next.js)

• React-based user interface
• TypeScript for type safety
• Tailwind CSS for styling
• File upload with drag-and-drop support
• Download functionality using invite codes

Prerequisites

• Java 17 or higher
• Maven 3.6 or higher
• Node.js 18 or higher
• npm or yarn package manager

Getting Started

1. Start the Backend Server

mvn clean package
java -jar target/p2p-1.0-SNAPSHOT.jar

The backend server will start on port 8080.

2. Start the Frontend

cd ui
npm install
npm run dev

The frontend will be available at http://localhost:3000.

Usage

Sharing a File

1. Navigate to the "Share a File" tab
2. Drag and drop or select a file to upload
3. Receive an invite code (port number)
4. Share the invite code with the recipient

Receiving a File

1. Navigate to the "Receive a File" tab
2. Enter the invite code provided by the sender
3. Click "Download File"
4. The file will be downloaded to your device

Project Structure

PeerLink/
├── src/main/java/p2p/          # Java backend source code
│   ├── App.java                # Main application entry point
│   ├── controller/             # HTTP request handlers
│   ├── service/                # File sharing business logic
│   └── utils/                  # Utility classes
├── ui/                         # Next.js frontend
│   ├── src/app/               # Application pages
│   ├── src/components/        # React components
│   └── package.json           # Frontend dependencies
├── target/                     # Compiled Java classes
├── pom.xml                     # Maven configuration
└── README.md                   # This file

Building for Production

Backend

mvn clean package

Frontend

cd ui
npm run build
npm start

Technical Details

• Backend uses Java's built-in HTTP server
• File transfers use TCP sockets for direct peer communication
• Frontend communicates with backend via REST API
• CORS enabled for cross-origin requests
• Temporary file storage in system temp directory
• Automatic cleanup of transferred files

License

This project is available for educational and personal use.