send and receive data from and to kotlin class

bluetooth_viewmodel.dart

const String CHANNEL_NAME = 'bluetooth.channel';
const bluetoothPlatform = const MethodChannel(CHANNEL_NAME);
const String BLUETOOTH_LIST_HEADER = "Bluetooth Devices";
const String INITIALIZE_BLUETOOTH_ADAPTER = "getBlue";
const String CONNECT_DEVICE = "connectDevice";
const String DISCONNECT_DEVICE = "disconnectSocket";
const String DISCOVER_DEVICE = "discoverBlue";
const String PAIRED_DEVICE = "allPaired";

void initBluetooth() async {
    await bluetoothPlatform.invokeMethod(INITIALIZE_BLUETOOTH_ADAPTER);
  }

 Future<List<BluetoothDevice>> getBondedDevices() async {
    var devices = await bluetoothPlatform.invokeMethod(PAIRED_DEVICE);
    if(devices != null) {
      Iterable l = json.decode(devices.toString());
      return List<BluetoothDevice>.from(
          l.map((model) => BluetoothDevice.fromJson(model)));
    }
    return List<BluetoothDevice>.empty();
  }

  Future<List<BluetoothDevice>> getDiscoveredDevice() async {
    var devices = await bluetoothPlatform.invokeMethod(DISCOVER_DEVICE);
    if(devices != null) {
      Iterable l = json.decode(devices.toString());
      return List<BluetoothDevice>.from(
          l.map((model) => BluetoothDevice.fromJson(model)));
    }
    return List<BluetoothDevice>.empty();
  }

  void connectToDevice(BluetoothDevice device) async {
    var data = json.encode(device);
    await bluetoothPlatform.invokeMethod(CONNECT_DEVICE, data);
  }

  void disconnectFromDevice() async {
    await bluetoothPlatform.invokeMethod(DISCONNECT_DEVICE);
  }