PeerConnect 📱🔗

Serverless. Private. Resilient.

PeerConnect is an offline-first, peer-to-peer (P2P) messaging application for Android. It enables devices to create a local mesh network via Wi-Fi P2P and Bluetooth Low Energy (BLE), allowing for secure chat and file transfer without an internet connection, cellular data, or a centralized server.

It is designed for high-interference environments, subways, airplanes, or remote locations where traditional connectivity fails.

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📥 Download

Download the latest APK here

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🌟 Key Features

📡 Connectivity & Discovery

• 100% Offline: Operates entirely on the device's radio hardware (Bluetooth/Wi-Fi).
• Hybrid Discovery Engine:
  • Auto-Connect: Uses a background algorithm to automatically detect and reconnect to known "friends" without user intervention.
  • Scan & Select: A manual "Pairing Mode" that scans for unknown devices and presents a selection list, preventing accidental connections to strangers.
• Location Enforcer: Automatically handles Android's strict location/GPS requirements for P2P discovery (Android 10 through 14+).

💬 Messaging & Data

• End-to-End Encryption: Messages are AES-encrypted locally before transmission, ensuring privacy even over open airwaves.
• File Sharing: Supports binary stream transfer for images and documents. Files are automatically saved to the system Downloads folder using the MediaStore API.
• Resilient Queuing: If a device disconnects mid-chat, messages are queued locally in a Room Database and auto-flushed upon reconnection.

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🛠️ Tech Stack

• Language: Kotlin
• Connectivity: Google Nearby Connections API (Strategy: P2P_STAR)
• Database: Android Room (SQLite abstraction) for persistence.
• Concurrency: Kotlin Coroutines & lifecycleScope.
• Architecture: Event-Driven Activity (Refactoring to MVVM in progress).

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📖 How It Works

1. The "Heartbeat" Loop (Auto-Connect)

Unlike standard Bluetooth, the Nearby Connections API requires one device to be an Advertiser and one to be a Discoverer. To solve the "who connects to whom" problem without a server, PeerConnect implements a Randomized Role Switching Loop:

1. Device A starts Scanning.
2. Device B starts Advertising.
3. If no connection is made within X seconds, they swap roles.
4. Ghost Timer Fix: A custom handler ensures that role-switching timers are cancelled immediately upon connection to prevent the radio from resetting during an active chat.

2. The Pairing Handshake (Manual)

When adding a new contact, the app suspends the auto-loop and enters Pairing Mode:

1. Host: Broadcasts availability securely.
2. Joiner: Scans for signals and filters them into a temporary list.
3. Selection: The user is presented with a dialog of found devices. Connection is only initiated when a specific peer is tapped.
4. Identity: Devices exchange cryptographically generated IDs and nicknames.

3. Data Transmission

• Text: Serialized Java Objects converted to Byte Payloads.
• Files: Payload.Type.FILE utilizes ParcelFileDescriptor to stream data directly from storage to storage, bypassing memory limits.

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🚀 Installation & Setup

1. Clone the repository:

   git clone https://github.com/SilentFURY-x/PeerConnect-App.git

2. Open in Android Studio: Ensure you are using the latest version (Hedgehog or newer).
3. Permissions: The app requests the following runtime permissions:
   • BLUETOOTH_SCAN / ADVERTISE / CONNECT
   • ACCESS_FINE_LOCATION
   • NEARBY_WIFI_DEVICES (Android 13+)
4. Build & Run:
   • Deploy to two physical Android devices.
   • Note: Android Emulators do not support Bluetooth/Wi-Fi P2P protocols.

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📂 Project Structure

com.fury.peerconnect
├── data
│   ├── database       # Room Database setup
│   ├── daos           # Data Access Objects (PeerDao, MessageDao)
│   └── entities       # Data classes (PeerEntity, MessageEntity)
├── logic
│   ├── UserManager    # Identity & SharedPrefs wrapper
│   └── SecurityHelper # AES Encryption logic
├── ui
│   ├── adapters       # RecyclerView Adapters for Chat/Peers
│   └── MainActivity.kt # Core Radio Logic & UI Controller

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🔮 Future Roadmap

• Background Service: Implement a Foreground Service to keep the radio alive when the app is minimized.
• Mesh Networking: Implement routing logic to allow Device A to talk to Device C via Device B.
• Voice Calls: WebRTC implementation over the offline socket for real-time audio.
• MVVM Refactor: Migrate UI logic from Activity to ViewModels for better testability.

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🤝 Contributing

Contributions are what make the open-source community such an amazing place to learn, inspire, and create. Any contributions you make are greatly appreciated.

1. Fork the Project

2. Create your Feature Branch:

   git checkout -b feature/AmazingFeature

3. Commit your Changes:

   git commit -m 'Add some AmazingFeature'

4. Push to the Branch:

   git push origin feature/AmazingFeature

5. Open a Pull Request

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📄 License

Distributed under the MIT License. See LICENSE for more information.

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👨‍💻 Author

Arjun Tyagi

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Built with ❤️ by Arjun Tyagi