Rapid Transfer - Cross-Platform File Transfer App

A fast, secure, and easy-to-use file transfer application for local networks, supporting Android, Windows, and macOS.

Overview

Rapid Transfer enables seamless file sharing between devices on the same local network with:

Zero configuration - automatic device discovery using UDP broadcast
Fast transfers - multi-stream parallel connections for maximum speed
Secure - TLS 1.3 encryption with device verification
Resume capability - interrupted transfers can be resumed
Cross-platform - works between Android, Windows, and Mac devices
User-friendly - icon-driven interface with minimal text
Bilingual - English and Indonesian (Bahasa Indonesia) support

Features

Core Capabilities

Automatic device discovery on local networks
Multi-stream transfers (1-8 parallel streams based on file size)
TLS 1.3 encrypted transfers
Device pairing with verification codes (like Bluetooth pairing)
Resume interrupted transfers
Folder compression (automatic tar.gz)
SHA-256 checksums for data integrity
Queue management with progress tracking

Desktop (Electron/Node.js)

Drag-and-drop file transfer
Device cards with connection status
Transfer queue with detailed progress
Settings for stream count, language, notifications
macOS Universal DMG and Windows NSIS installer

Mobile (Flutter/Android)

Share intent support (send from any app)
File picker and gallery picker
Swipeable transfer queue
Hotspot mode for direct connections
WiFi Direct support (Android-to-Android)
Wake lock to prevent sleep during transfers
Battery monitoring with warnings

Project Structure

.
├── desktop_app/          # Electron desktop application
│   ├── src/
│   │   ├── main.js       # Main process
│   │   ├── preload.js    # Context bridge
│   │   ├── services/     # Discovery, transfer, device management
│   │   └── ui/           # HTML/CSS/JS renderer
│   └── package.json
│
├── mobile_app/           # Flutter mobile application
│   ├── lib/
│   │   ├── main.dart     # App entry point
│   │   ├── models/       # Data models
│   │   ├── services/     # Business logic
│   │   ├── screens/      # UI screens
│   │   ├── widgets/      # Reusable widgets
│   │   └── l10n/         # Localization files
│   └── pubspec.yaml
│
└── scripts/              # Build and deployment scripts

Getting Started

Desktop App

Prerequisites:

Node.js 20+
npm 10+

cd desktop_app
npm install
npm start                 # Development
npm run build             # Build for current platform
npm run build:mac         # Build for macOS
npm run build:win         # Build for Windows

Mobile App

Prerequisites:

Flutter 3.9.2+
Android SDK
JDK 17

cd mobile_app
flutter pub get
flutter run               # Development
flutter build apk         # Build APK

Or use the provided scripts:

./scripts/build_apk.sh
./scripts/build_aab.sh

Network Architecture

Discovery

Protocol: UDP Broadcast
Port: 8766 (discovery only)
Broadcast: Device name, ID, platform, version (JSON format)
Frequency: Every 5 seconds
Timeout: 30 seconds (devices not seen are removed)
Works on ALL platforms without any external dependencies

Transfer Protocol

Transport: TCP with TLS 1.3
Port: 8765 (file transfers)
Streams: Dynamic (1-8 based on file size)
- < 10 MB: 1 stream
- 10-100 MB: 2 streams
- 100 MB - 1 GB: 4 streams
- > 1 GB: 6 streams
Chunks: 1 MB for granular progress and resume
Verification: SHA-256 checksums per chunk and full file

Security

TLS 1.3 encryption for all transfers
Certificate pinning after first pairing
Device verification with random 3-digit codes
No passwords needed or stored
Man-in-the-middle protection

Localization

The app supports:

English: Standard interface
Indonesian (Bahasa Indonesia): Simple, accessible language designed for users in Papua with limited formal education

Common terms:

Send = Kirim
Receive = Terima
Device = Perangkat
File = File
Transfer = Transfer

User Workflow

Discovery: App automatically discovers other Rapid Transfer devices on the network
Pairing: First-time connection shows a verification code on both devices
Trust: Users confirm the code matches and accept to trust the device
Transfer: Drag-and-drop files (desktop) or use share/file picker (mobile)
Progress: Real-time progress with speed, ETA, and queue management
Resume: If interrupted, transfers auto-resume when devices reconnect

Performance Targets

Discovery latency: < 2 seconds on same LAN
Transfer speed: ≥ 10 Mbps on modern WiFi (802.11ac+)
Resume latency: < 5 seconds after reconnection
Memory usage: < 500 MB for 10 GB file transfer
File size: No hard limit (tested with multi-GB files)

Development Status

This is the initial implementation including:

✅ Project structure for desktop and mobile
✅ Basic UI frameworks
✅ Device discovery infrastructure
✅ Transfer service architecture
✅ Localization support (English and Indonesian)
✅ Settings management
🚧 Network protocol implementation (in progress)
🚧 Multi-stream transfer logic (in progress)
🚧 Resume mechanism (in progress)
🚧 File compression (in progress)
🚧 Android-specific features (hotspot, WiFi Direct)

Contributing

This project follows these principles:

Minimal text, maximum icons - UI should be comprehensible without reading
Simple language - Especially in Indonesian translations
Zero configuration - Users shouldn't need to know IP addresses or network settings
Security by default - All transfers encrypted, devices verified
Fail gracefully - Clear error messages and recovery options

License

AGPL-3.0 License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.

Network Use Notice: If you modify this software and make it available over a network, you must make the source code of your modifications available under AGPL-3.0.

See LICENSE.md for full license text and third-party attributions.

Acknowledgments

This software was developed with the assistance of:

GitHub Copilot - AI-powered code completion
VS Code Copilot Agent (Claude Sonnet 4.5) - AI development assistant

Support

For issues, questions, or contributions, please open an issue on GitHub.

rulingAnts / cross_platform_file_transfer_app