PeerLink - P2P File Sharing Application

PeerLink is a peer-to-peer file sharing application that allows users to share files directly between devices using a simple invite code system.

Drag and Drop File Upload

This feature allows users to quickly share files without traditional file explorers.

Project Structure

• src/main/java/p2p: Java backend code
  • App.java: Main application entry point
  • controller/: API controllers
  • service/: Business logic services
  • utils/: Utility classes
• ui/: Next.js frontend application
  • src/app: Next.js app router pages
  • src/components: React components

Features

• Drag and drop file upload
• File sharing via invite codes (port numbers)
• File downloading using invite codes
• Modern, responsive UI
• Direct peer-to-peer file transfer

Prerequisites

• Java 11+ (for the backend)
• Node.js 18+ and npm (for the frontend)
• Maven (for building the Java project)

Getting Started

Quick Start

Linux/macOS:

./start.sh

Windows:

start.bat

These scripts will build the Java backend, start the server, and launch the frontend development server.

Manual Setup

Backend Setup

1. Build the Java project:

mvn clean package

2. Run the backend server:

java -jar target/p2p-1.0-SNAPSHOT.jar

The backend server will start on port 8080.

Frontend Setup

1. Install dependencies:

cd ui
npm install

2. Run the development server:

npm run dev

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

How It Works

1. File Upload:

   • User uploads a file through the UI
   • The file is sent to the Java backend
   • The backend assigns a unique port number (invite code)
   • The backend starts a file server on that port

2. File Sharing:

   • The user shares the invite code with another user
   • The other user enters the invite code in their UI

3. File Download:

   • The UI connects to the specified port
   • The file is transferred directly from the host to the recipient

Architecture

┌─────────────┐     ┌─────────────┐     ┌─────────────┐
│             │     │             │     │             │
│  Next.js UI │◄────►│ Java Server │◄────►│ Peer Device │
│             │     │             │     │             │
└─────────────┘     └─────────────┘     └─────────────┘

Low Level Design (LLD)

classDiagram
    %% Frontend Components
    class NextJSApp {
        +handleFileUpload()
        +handleFileDownload()
        +connectToPeer()
    }
    
    class FileUploadComponent {
        +handleDragDrop()
        +validateFile()
        +uploadFile()
    }
    
    class FileDownloadComponent {
        +enterInviteCode()
        +downloadFile()
        +showProgress()
    }
    
    %% Backend Components
    class App {
        +main()
        +startServer()
    }
    
    class FileController {
        +uploadFile()
        +generateInviteCode()
        +validateInviteCode()
    }
    
    class FileService {
        +storeFile()
        +createFileServer()
        +handleFileTransfer()
    }
    
    class FileUtils {
        +validateFile()
        +generatePort()
        +cleanupResources()
    }
    
    %% Relationships
    NextJSApp --> FileUploadComponent
    NextJSApp --> FileDownloadComponent
    FileUploadComponent --> FileController
    FileDownloadComponent --> FileController
    FileController --> FileService
    FileService --> FileUtils
    
    %% Data Flow
    class DataFlow {
        FileUpload
        FileDownload
        InviteCode
        PortNumber
    }
    
    %% Component Notes
    note for NextJSApp "Handles UI state and user interactions"
    note for FileController "REST API endpoints for file operations"
    note for FileService "Core business logic for file handling"
    note for FileUtils "Utility functions for file operations"

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Component Details

Frontend Components

• NextJSApp: Main application component managing state and routing
• FileUploadComponent: Handles drag-and-drop file uploads
• FileDownloadComponent: Manages file downloads using invite codes

Backend Components

• App: Main application entry point and server initialization
• FileController: REST API endpoints for file operations
• FileService: Core business logic for file handling
• FileUtils: Utility functions for file validation and port management

Data Flow

• File uploads are handled through drag-and-drop
• Invite codes (port numbers) are generated for sharing
• Direct peer-to-peer file transfer using WebSocket connections

Security Considerations

• Files are stored temporarily in the system's temp directory
• Each file gets a unique filename to prevent conflicts
• Port numbers are randomly generated in the dynamic port range (49152-65535)
• CORS is enabled for cross-origin requests

Deployment

Local Development

For local development and testing, use the startup scripts as described in the "Getting Started" section above.

Production Deployment (AWS with Nginx)

PeerLink can be deployed to AWS EC2 with Nginx as a reverse proxy for production use.

Quick Deployment Steps

1. Launch EC2 Instance

   • Ubuntu 22.04 LTS
   • t3.medium or larger
   • Configure security group (see deployment/SECURITY_GROUP.md)
   • Allocate Elastic IP

2. Upload Application

   scp -i your-key.pem -r p2p ubuntu@your-ec2-ip:/home/ubuntu/peerlink

3. Run Deployment Script

   ssh -i your-key.pem ubuntu@your-ec2-ip
   cd /home/ubuntu/peerlink
   chmod +x deployment/deploy.sh
   ./deployment/deploy.sh

4. Configure Domain & SSL

   # Update Nginx config with your domain
   sudo nano /etc/nginx/sites-available/peerlink
   
   # Setup SSL certificate
   sudo certbot --nginx -d your-domain.com

Deployment Documentation

• Comprehensive Guide: See deployment/README.md
• Deployment Checklist: See deployment/DEPLOYMENT_CHECKLIST.md
• Security Group Setup: See deployment/SECURITY_GROUP.md
• Full AWS Plan: See .gemini/antigravity/brain/.../aws_deployment_plan.md

Cost Estimate

• Single EC2 instance (t3.medium): ~$40-80/month
• Includes compute, storage, and data transfer

Production Architecture

Internet → Nginx (443) → Next.js (3000) → Java Backend (8080)
                ↓
         P2P Ports (49152-65535)

For detailed deployment instructions, troubleshooting, and best practices, refer to the documentation in the deployment/ directory.

License

This project is open source and available under the MIT License.