LinkerNet

LinkerNet is a local network emergency communication system designed to enable real-time chat between devices connected to the same Wi-Fi or LAN, even when internet connectivity is lost. It is ideal for use during disasters and emergency situations, allowing easy, reliable peer communication using a lightweight backend and a responsive web-based frontend.

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Table of Contents

• Introduction
• Project Structure
• How It Works
• Tech Stack
• Getting Started
  • Running the Backend
  • Running the Frontend
• Using LinkerNet on a Local Network
• Chatting Across Devices
• Screenshots

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Introduction

LinkerNet facilitates offline-first, peer-to-peer chat within a local network environment. When traditional communication channels fail during emergencies, LinkerNet allows users to connect via a local Wi-Fi or LAN, share messages in real time, and coordinate relief efforts or share vital information.

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Project Structure

LinkerNet/
├── backend/                    # Spring Boot backend service
│   ├── src/main/java/
│   │   └── com/LinkerNet/
│   │       ├── LinkerNetApplication.java         # Main Spring Boot app
│   │       ├── config/                            # Configuration (CORS, WebSocket)
│   │       ├── controller/                        # REST and WebSocket controllers
│   │       ├── model/                             # JPA entities (Message)
│   │       ├── repository/                        # Data access layer
│   │       └── service/                           # Business logic layer
│   └── resources/
│       └── application.properties                 # Application settings (DB, CORS, ports)
├── frontend/                   # React frontend app (Vite + Tailwind CSS)
│   ├── src/
│   │   └── App.jsx                               # React main component with STOMP + SockJS
│   ├── public/                                   # Public assets
│   ├── index.html                                # Root HTML
│   └── vite.config.js                            # Vite config for dev server and build
└── README.md                                   # This file

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How It Works

1. The backend is a Spring Boot application running as a chat server, exposing:

   • REST API to fetch chat history (/api/messages),
   • WebSocket endpoint /chat using STOMP over SockJS for real-time messaging.

2. The frontend is a React app that:

   • Fetches chat history on load,
   • Connects to backend WebSocket via SockJS + STOMP,
   • Sends/receives chat messages in real time,
   • Displays a modern, responsive chat UI.

3. Messages sent from any device are broadcasted to all connected devices on the same network via the local backend server.

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Tech Stack

• Backend:

  • Java with Spring Boot
  • Spring WebSocket with STOMP messaging
  • JPA + Hibernate + MySQL for message persistence
  • CORS and WebSocket configuration

• Frontend:

  • React
  • Vite development server
  • Tailwind CSS for styling
  • @stomp/stompjs client for STOMP over SockJS WebSocket support
  • Axios for REST API calls

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Getting Started

Running the Backend

1. Ensure you have Java 17+ and Maven installed.
2. Build the backend jar:

   mvn clean package
   

3. Run the backend server:

   java -jar target/disasternet-backend.jar
   

4. Backend listens on port 8080 by default.

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Running the Frontend

1. Navigate to the frontend directory.
2. Install dependencies:

   npm install
   

3. Start the development server (accessible in browser):

   npm run dev
   

4. By default, frontend runs on port 5173.

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Using LinkerNet on a Local Network

1. Connect all devices (laptop, phones, tablets) to the same Wi-Fi or LAN.

2. Identify your laptop's local IP address (where backend runs):

   • On Windows: open Command Prompt, run ipconfig, find IPv4 address.
   • On macOS/Linux: run ifconfig or ip a, find local IP.

3. Update frontend backend connection in App.jsx:

   const backendHost = "192.168.x.y"; // Replace with your laptop's IP
   

4. Rebuild frontend if needed and serve it (or run dev server bound to all interfaces).

5. Open browser on phones or other LAN devices:

   http://192.168.x.y:5173
   

6. Devices will connect to the backend server running on the laptop on port 8080 and chat in real time.

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Chatting Across Devices

• Open the frontend page on all devices.
• Enter a nickname (optional).
• Type messages and send by pressing Enter or Send button.
• Messages appear instantly on all connected devices.
• Messages are stored persistently in the backend’s MySQL database.
• Supports offline-first experience as long as devices remain connected to the same network.

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Screenshots

(Add screenshot images of your app here — replace paths with your actual screenshots)

Chat on Laptop	Chat on Mobile Browser

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Contact & Support

For issues, feature requests, or contributions, please open an issue or pull request on the GitHub repository.

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Thank you for using LinkerNet — your reliable local network emergency chat!

By Shivam Kumar / Shivammiyyy