btclip

Offline bidirectional clipboard and screenshot sync between Android and Windows over Bluetooth RFCOMM.

btclip pairs a Windows Rust host and an Android Kotlin client using raw Bluetooth SPP without internet or cloud services.

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Features

• Private Bluetooth Sync: Clipboard and image data move directly over RFCOMM.
• Bidirectional Text: Copy from Android to PC or from PC to Android.
• Screenshot Image Transfer: Send screenshots from phone to PC as image clipboard payloads.
• Lightweight: Rust host plus Kotlin client keep the app footprint small.
• Frame Protocol: Uses a fixed 5-byte frame header for robust stream parsing.

Architecture

Component	Location	Role
PC Host	Repository root	Rust RFCOMM server, Windows clipboard bridge, binary frame parser/encoder.
Android App	client/	Kotlin foreground client, Bluetooth SPP, clipboard bridge, FileProvider image sharing.
Transport	Bluetooth RFCOMM	Standard SPP UUID 00001101-0000-0000-0000-00805F9B34FB for raw socket transport.

Wire Protocol Spec

Frames are encoded as:

[1-byte Type][4-byte Big-Endian Length][Payload]

• 0x01 = UTF-8 text
• 0x02 = PNG/JPEG image bytes
• Length = Big-endian unsigned 32-bit payload size
• Payload = exact text or image bytes

Project Structure

btclip/
├── Cargo.toml
├── src/
│   ├── main.rs
│   ├── bluetooth.rs
│   ├── clipboard.rs
│   └── protocol.rs
└── client/
    ├── build.gradle.kts
    ├── gradle.properties
    ├── settings.gradle.kts
    ├── gradle/
    │   └── wrapper/
    ├── gradlew
    ├── gradlew.bat
    └── app/
        ├── build.gradle.kts
        └── src/main/
            ├── AndroidManifest.xml
            ├── java/com/forgata/btclip/
            │   ├── MainActivity.kt
            │   └── ProtocolParser.kt
            └── res/xml/file_paths.xml

Android Client Notes

The Android code is isolated under client/. The client includes:

• MainActivity.kt for runtime permission requests
• ProtocolParser.kt for RFCOMM frame parsing over an InputStream
• AndroidManifest.xml with Bluetooth and foreground service permissions
• file_paths.xml to share cache files through FileProvider

Installation

Build the PC Host

From the repository root:

cargo build --release

Run the host binary:

.\target\release\btclip.exe

Build the Android Client

From the client/ directory:

cd client
.\gradlew.bat assembleDebug --no-daemon

Or on Unix-like shells:

cd client
./gradlew assembleDebug --no-daemon

Install the Android APK

Using the Gradle wrapper:

cd client
.\gradlew.bat installDebug

Or directly with ADB after building:

adb install -r app\build\outputs\apk\debug\app-debug.apk

Usage

1. Pair your Android phone and Windows PC in system Bluetooth settings.
2. Start the PC host binary.
3. Install and run the Android client.
4. Grant Bluetooth and notification permissions when prompted.
5. Use clipboard copy on either side to sync text or images.

Notes

• Keep Android source strictly inside client/.
• The host lives in the repository root as a Rust crate.
• client/ already includes Gradle wrapper files for CLI builds.