flutter reactive ble problem trying to connect to specific device - flutter

Question

flutter_reactive_ble code for the main page which will connect to a device name "BT05" when we press the button and send a string value "B" and receive the value response from the device and print it on the screen, I have posted my code here as well for reference but I don't know what I'm doing wrong here, please help me with this as I'm stuck for long enough now and tried many ways to it. i have also used some other flutter libraries but none of them worked well
import 'package:flutter_reactive_ble/flutter_reactive_ble.dart';
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Reactive BLE',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Reactive BLE'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String _deviceName = "BT05";
String _value = "B";
String _responseValue = "";
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Flutter BLE Demo'),
),
body: Column(
children: <Widget>[
ElevatedButton(
child: Text('Connect to $_deviceName'),
onPressed: () async {
// Connect to device
final stateUpdate = await FlutterReactiveBle.instance
.connectToDevice(_deviceName);
stateUpdate.listen((s) {
if (s == ConnectionState.disconnected) {
// Disconnected state
} else if (s == ConnectionState.connected) {
// Connected state
// Send value
FlutterReactiveBle.instance
.writeCharacteristic(_deviceName, _value)
.then((value) {
// Response value
_responseValue = value;
});
}
});
},
),
Text('Response value: $_responseValue')
],
),
);
}
}