Flutter TCP File Sharing App

A cross-platform Flutter application for file sharing and messaging over TCP sockets, supporting multi-client connections, QR code scanning for easy server discovery, and file previews. The app is designed to work seamlessly on both iOS and Android, with platform-specific handling for file paths and socket communication.

Features

• Multi-Client Support: Connect multiple clients (iOS/Android) to a single server for simultaneous file sharing and messaging.
• File Sharing: Send and receive files (e.g., images, PDFs, text) with size verification and error handling.
• Real-Time Messaging: Exchange text messages between server and clients with reliable delivery.
• QR Code Scanning: Scan QR codes to auto-connect clients to the server using the mobile_scanner package.
• File Previews: Preview received files (e.g., PDFs, images) using flutter_pdfview and image packages.
• Platform-Specific Handling: Optimized for iOS (sandboxed file paths) and Android (direct file access).
• State Management: Uses flutter_bloc for robust state management of server and client operations.
• Error Handling: Comprehensive logging and UI feedback for connection, file transfer, and header parsing errors.

Prerequisites

• Flutter SDK: Version 3.24.0 or higher.
• Dart: Version 3.5.0 or higher.
• Devices: iOS 14.0+ or Android 7.0+.
• Network: Devices must be on the same Wi-Fi network for TCP communication.
• IDE: Android Studio, VS Code, or any Flutter-compatible IDE.

Installation

1. Clone the Repository:

   git clone <repository-url>
   cd flutter-tcp-file-sharing

2. Install Dependencies: Ensure pubspec.yaml contains the following dependencies, then run:

   flutter pub get

3. Configure iOS Permissions: Update ios/Runner/Info.plist to include:

   <key>NSPhotoLibraryUsageDescription</key>
   <string>Access photos for file sharing</string>
   <key>NSFileProviderDomainUsageDescription</key>
   <string>Access files for sharing</string>
   <key>NSCameraUsageDescription</key>
   <string>Access camera for QR code scanning</string>

4. Run the App:

   flutter run

Dependencies

Below are the key dependencies used in the project, with keywords for their purpose:

• flutter_bloc: ^8.1.3
  • Keywords: State management, BLoC pattern, reactive UI
  • Manages server and client states (ServerBloc, ClientBloc) for robust UI updates.
• path_provider: ^2.1.1
  • Keywords: File system, storage, cross-platform
  • Accesses app-specific directories for file storage and retrieval.
• mobile_scanner: ^7.0.1
  • Keywords: QR code, barcode, camera
  • Enables QR code scanning for server IP/port discovery.
• file_picker: ^8.0.0
  • Keywords: File selection, cross-platform, file access
  • Allows users to pick files for sharing from device storage.
• uuid: ^4.4.2
  • Keywords: Unique ID, UUID generation
  • Generates unique file IDs for tracking file transfers.
• open_file_plus: ^4.0.0
  • Keywords: File opening, cross-platform
  • Opens received files (e.g., PDFs, images) in native viewers.
• flutter_pdfview: ^1.3.2
  • Keywords: PDF viewer, file preview
  • Displays PDF files in the app for previewing.
• image: ^4.2.0
  • Keywords: Image processing, file preview
  • Handles image file previews and rendering.

Add these to your pubspec.yaml:

dependencies:
  flutter:
    sdk: flutter
  flutter_bloc: ^8.1.3
  path_provider: ^2.1.1
  mobile_scanner: ^7.0.1
  file_picker: ^8.0.0
  uuid: ^4.4.2
  open_file_plus: ^4.0.0
  flutter_pdfview: ^1.3.2
  image: ^4.2.0

Usage

1. Start the Server:

   • Launch the app on a device (e.g., Android tablet).
   • Navigate to the ServerScreen.
   • Start the server (default port: 5000).
   • Note the IP address and QR code displayed.

2. Connect Clients:

   • On client devices (iOS/Android), open the ClientScreen.
   • Scan the QR code or manually enter the server IP and port.
   • Connect to the server.

3. Send Messages:

   • On ClientScreen, type a message and press the send button.
   • On ServerScreen, send messages to all connected clients.
   • Messages appear in the MessageListWidget on both screens.

4. Share Files:

   • On ClientScreen, tap the attach file button to pick a file.
   • Files are sent to the server and appear in FileListWidget.
   • Tap files in FileListWidget to preview or download.

5. Preview Files:

   • Received files (e.g., PDFs, images) can be previewed by tapping in FileListWidget or MessageListWidget.
   • Uses flutter_pdfview for PDFs and image for images.

Project Structure

• blocs/
  • server/server_bloc.dart: Manages server operations (start, stop, send/receive messages/files).
  • client/client_bloc.dart: Handles client connections and file/message transfers.
• screens/
  • server_screen.dart: UI for starting/stopping server and managing transfers.
  • client_screen.dart: UI for connecting to server and sending/receiving data.
• widgets/
  • file_list_widget.dart: Displays available files with preview/download options.
  • message_list_widget.dart: Shows message history with file attachments.
• models/
  • message_model.dart: Data model for messages and file metadata.

Troubleshooting

• Connection Issues:
  • Ensure all devices are on the same Wi-Fi network.
  • Verify port 5000 is open (telnet <ip> 5000 or nc <ip> 5000).
  • Check server logs for Server running at <ip>:5000.
• Invalid Header Errors:
  • Share server logs (Raw header received, Invalid header).
  • Test with simple file names (e.g., test.txt).
  • Verify iOS file paths are copied to app directory.
• Messages Not Sent/Received:
  • Check client logs for Sending header, Error sending message.
  • Ensure server logs show Received message: <text>.
• iOS File Issues:
  • Confirm Info.plist permissions for camera and file access.
  • Verify file copy logs in ClientScreen.
• File Previews:
  • Ensure flutter_pdfview and image packages are correctly installed.
  • Test with supported file types (PDF, JPEG, PNG).

Known Limitations

• Security: Uses unencrypted TCP; consider SSL/TLS for production.
• File Size: Large files may require chunked transfer optimizations.
• Network: Requires same Wi-Fi network; no internet support.
• Error Recovery: Limited retry logic for failed transfers.

Future Enhancements

• Add SSL/TLS for secure communication.
• Implement file transfer progress indicators.
• Support internet-based connections via WebSocket.
• Add retry mechanism for failed messages/files.
• Include file checksums for integrity verification.

Contributing

1. Fork the repository.
2. Create a feature branch (git checkout -b feature/<name>).
3. Commit changes (git commit -m "Add feature").
4. Push to branch (git push origin feature/<name>).
5. Open a pull request.

License

MIT License. See LICENSE for details.