Blekit

blekit is a lightweight, dependency-free Bluetooth Low Energy (BLE) library for React Native and Expo. It is written in 100% pure Swift (utilizing CoreBluetooth) on iOS and 100% pure Kotlin (utilizing standard android.bluetooth) on Android.

It provides a drop-in replacement for the react-native-ble-plx API, removing all heavy reactive programming dependencies (such as RxBluetoothKit, RxAndroidBle, RxSwift, and RxJava) to deliver faster builds, a smaller bundle size, and fewer compilation issues.

Features

• Bluetooth state monitoring.
• Device scanning with UUID filtering.
• Connection management (connect, disconnect, connection status, RSSI reading).
• GATT Service and Characteristic discovery.
• Characteristic read and write operations (with and without response).
• Characteristic monitoring (notifications and indications).
• Descriptor read and write operations.
• MTU and connection priority requests.

Installation

npm install blekit
# or
yarn add blekit

Expo Configuration

Because this module contains custom native code, it cannot run in the standard Expo Go client. You must use Development Builds.

Add permissions to your Expo app.json or app.config.js:

{
  "expo": {
    "plugins": [
      [
        "expo-build-properties",
        {
          "ios": {
            "deploymentTarget": "16.4"
          }
        }
      ]
    ],
    "ios": {
      "infoPlist": {
        "NSBluetoothAlwaysUsageDescription": "This app uses Bluetooth to connect to BLE devices."
      }
    },
    "android": {
      "permissions": [
        "android.permission.BLUETOOTH",
        "android.permission.BLUETOOTH_ADMIN",
        "android.permission.BLUETOOTH_SCAN",
        "android.permission.BLUETOOTH_CONNECT",
        "android.permission.ACCESS_FINE_LOCATION"
      ]
    }
  }
}

Then prebuild and run:

npx expo prebuild
npx expo run:ios
npx expo run:android

Usage

Here is a quick example showing how to initialize the manager, scan for devices, connect, and read/write values.

import { BleManager, Device, Characteristic } from 'blekit';

// Initialize the manager (create it only once, usually as a singleton)
const manager = new BleManager();

// 1. Monitor Bluetooth state changes
const stateSub = manager.onStateChange((state) => {
  console.log('Bluetooth state changed:', state); // e.g., 'PoweredOn'
}, true);

// 2. Scan for devices
manager.startDeviceScan(null, null, (error, device) => {
  if (error) {
    console.error('Scan error:', error);
    return;
  }
  
  if (device) {
    console.log(`Discovered device: ${device.name} (${device.id})`);
    
    // Stop scanning when your target device is found
    if (device.name === 'MyBLEDevice') {
      manager.stopDeviceScan();
      connectToDevice(device);
    }
  }
});

// 3. Connect to device and discover services & characteristics
async function connectToDevice(device: Device) {
  try {
    console.log('Connecting...');
    const connectedDevice = await device.connect();
    console.log('Connected! Discovering services and characteristics...');
    
    await connectedDevice.discoverAllServicesAndCharacteristics();
    console.log('Discovered everything!');
    
    // Read a value
    const serviceUUID = '12345678-1234-5678-1234-567812345678';
    const charUUID = '87654321-4321-8765-4321-876543210987';
    
    const characteristic = await connectedDevice.readCharacteristicForService(
      serviceUUID,
      charUUID
    );
    console.log('Read base64 value:', characteristic.value);
    
    // Write a value (base64 encoded)
    const base64Value = 'SGVsbG8='; // 'Hello'
    await connectedDevice.writeCharacteristicWithResponseForService(
      serviceUUID,
      charUUID,
      base64Value
    );
    console.log('Write completed!');
    
    // Monitor characteristic value updates
    const monitorSub = connectedDevice.monitorCharacteristicForService(
      serviceUUID,
      charUUID,
      (err, char) => {
        if (err) {
          console.error('Notification error:', err);
          return;
        }
        console.log('New notified value:', char?.value);
      }
    );
    
  } catch (err) {
    console.error('Connection/GATT operations failed:', err);
  }
}

// 4. Cleanup when the manager is no longer needed
// manager.destroy();

API Difference from react-native-ble-plx

blekit maintains complete compatibility with the react-native-ble-plx API structure. You can replace:

import { BleManager } from 'react-native-ble-plx';

with:

import { BleManager } from 'blekit';

The underlying library takes care of translating your calls to native Swift/Kotlin commands without any third-party framework overhead.