characteristic.monitor().listen error while writeCharacteristic WithoutResponse as. my device is Notifiable

[philos3]

characteristic.monitor().listen throw an exception

my device is writewithoutresponse and is notifible
──────────────────────────────────────────────────────────
flutter: dataCharacteristic:
flutter: uuid: XXXXXXXXXXX(as example)
flutter: isReadable: false
flutter: isWritableWithoutResponse: true
flutter: isWritableWithResponse: false
flutter: isIndicatable: false
flutter: isNotifiable: true
──────────────────────────────────────────────────────────

as i set true to peripheral.writeCharacteristic( , , , true, ), there is no error on Android but ios got an error while writeCharacteristic
if i set false to peripheral.writeCharacteristic( , , , false, ), both android and ios got an error while monitor
what is the correct way to monitor and writeCharacteristic?

here is the error message
#####################

Unhandled error happened: Connection error has occured: - subscription called from:

characteristic.monitor().listen onError =====error:BleError (Error code: 201, ATT error code: null, iOS error code: null, Android error code: null, reason: Unknown error., internal message: null, device ID: CECAF6DD-73C5-B04C-EDE0-20B401AEF08B, service UUID: null, characteristic UUID: null, descriptor UUID: null)

here is my code
########################################
streamSubscription = characteristic.monitor().listen((readValue) {
///....
},onError: (error) {
LogUtil.e("characteristic.monitor().listen onError =====error:${error.toString()}===============================",tag: getClassName());
catchCharacteristicError(error, null);
} );

peripheral
.writeCharacteristic(
YsBleUuids.uuidService,
YsBleUuids.clientCharacteristicWithNotifyAndWrite,
Uint8List.fromList(value),
false,///while my dataCharacteristic. isWritableWithoutResponse: true. so withResponse is false
// transactionId:transactionId
)

########################################
(base) philos:flutter_beauty zby0520$ flutter doctor -v
[✓] Flutter (Channel stable, 2.2.3, on macOS 11.3 20E232 darwin-x64, locale zh-Hans-CN)
• Flutter version 2.2.3 at /Users/zby0520/flutter/flutter
• Framework revision f4abaa0735 (5 weeks ago), 2021-07-01 12:46:11 -0700
• Engine revision 241c87ad80
• Dart version 2.13.4
• Pub download mirror https://pub.flutter-io.cn
• Flutter download mirror https://storage.flutter-io.cn

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
• Android SDK at /Users/zby0520/Library/Android/sdk
• Platform android-30, build-tools 30.0.2
• ANDROID_SDK_ROOT = /Users/zby0520/Library/Android/sdk
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6916264)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 12.4, Build version 12D4e
• CocoaPods version 1.10.1

[✓] Chrome - develop for the web
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.2)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6916264)

[✓] IntelliJ IDEA Ultimate Edition (version 2020.1.3)
• IntelliJ at /Applications/IntelliJ IDEA.app
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart

[✓] Connected device (2 available)
• XXXXX (mobile) • XXXXXX• ios • iOS 14.4
• Chrome (web) • chrome • web-javascript • Google Chrome 91.0.4472.114

• No issues found!

[sh3rlock97]

Hi

Were you able to fix your error? I'm also getting a 201-Error when listening to a Characteristic:

if (characteristic.isNotifiable) {
   print("Notifiable: ${characteristic.uuid}");
   characteristic.monitor().listen(
       (event) {
         print("listend and heared ${event}");
       },
       onError: (e) => print("Error monitoring disconnect $e"),
       onDone: () {
         print("Disconnect!");
         peripheral.disconnectOrCancelConnection();
       },
       cancelOnError: true);
 }