BLE 通知订阅获得 133

Question

一部 Android 手机 (N5X 6.0.1) 正在运行 BLE 服务器，另一部 (N5X O) 正在订阅。可以启用特征通知，但是，在写入描述符部分，我始终得到 133。

Server.java

private void createServer() {
    bluetoothGattServer = bluetoothManager.openGattServer(this, serverCallback);
    BluetoothGattService service = new BluetoothGattService(Constants.SERVICE,
        BluetoothGattService.SERVICE_TYPE_PRIMARY);

    characteristic =
        new BluetoothGattCharacteristic(Constants.CHARACTERISTIC,
                BluetoothGattCharacteristic.PROPERTY_NOTIFY,
                BluetoothGattCharacteristic.PERMISSION_READ | BluetoothGattCharacteristic.PERMISSION_WRITE);

    // public static UUID DESCRIPTOR = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
    characteristic.addDescriptor(new BluetoothGattDescriptor(Constants.DESCRIPTOR,
                BluetoothGattCharacteristic.PERMISSION_READ | BluetoothGattDescriptor.PERMISSION_WRITE));

    characteristic.setWriteType(
        BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);

    service.addCharacteristic(characteristic);
    bluetoothGattServer.addService(service);
}

private BluetoothGattServerCallback serverCallback = new BluetoothGattServerCallback() {
    @Override
    public void onConnectionStateChange(BluetoothDevice device, int status, int newState) {
        super.onConnectionStateChange(device, status, newState);
        Log.d(TAG, "onConnectionStateChange " + device.getName() + " " + status + " " + newState);
        if (newState == BluetoothGatt.STATE_CONNECTED) {
            bluetoothDevice = device;
        } else if (newState == BluetoothGatt.STATE_DISCONNECTED) {
            bluetoothGattServer.cancelConnection(bluetoothDevice);
            bluetoothGattServer.close();
        }
    }
};

private void sendData(String message) {
    characteristic.setValue(message);
    bluetoothGattServer.notifyCharacteristicChanged(bluetoothDevice, characteristic, true);
}

所有其他 UUID 都是从这里创建的。

Client.java

device.establishConnection(false)
        .flatMap(bleConnection -> bleConnection.setupNotification(Constants.CHARACTERISTIC))
        .flatMap(onNotificationReceived -> onNotificationReceived)
        .subscribe(data -> {
            Log.d(TAG, "data: " + data);
        }, throwable -> {
            Log.d(TAG, "data error " + throwable);
        });

logcat

05-15 15:26:50.097 D/BluetoothGatt: setCharacteristicNotification() - uuid: 8d7dda32-3759-11e7-a919-92ebcb67fe33 enable: true
05-15 15:26:50.105 D/RxBle#Radio:   QUEUED RxBleRadioOperationDescriptorWrite(60042487)
05-15 15:26:50.110 D/RxBle#Radio: FINISHED RxBleRadioOperationServicesDiscover(231218312)
05-15 15:26:50.112 D/RxBle#Radio:  STARTED RxBleRadioOperationDescriptorWrite(60042487)
05-15 15:27:20.119 D/RxBle#Radio: FINISHED RxBleRadioOperationDescriptorWrite(60042487)
05-15 15:27:20.121 D/BluetoothGatt: setCharacteristicNotification() - uuid: 8d7dda32-3759-11e7-a919-92ebcb67fe33 enable: false
05-15 15:27:20.126 D/RxBle#BluetoothGatt: onDescriptorWrite descriptor=00002902-0000-1000-8000-00805f9b34fb status=133
05-15 15:27:20.129 D/BLE: data error BleGattDescriptorException{macAddress=42:EE:5A:C6:C1:F0, status=133 (0x85 -> https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/android-5.1.0_r1/stack/include/gatt_api.h), bleGattOperationType=BleGattOperation{description='DESCRIPTOR_WRITE'}}

注意：如果我使用原生 Android API，我可以订阅和接收通知而无需写入描述符。

更新：有趣的事情，虽然写描述符过程正在发生（大约需要 30 秒，直到它返回错误），我能够收到onCharacteristicChanged.

update2：添加回调并写入特征代码

Answer 1

蓝牙核心规范规定，如果某个特性支持通知，则它应该包含客户端特性配置描述符，并且仅当 CCC 描述符写入正确的值时才开始通知。

您的配置中似乎存在问题，表现为status = 133。看来您在设置属性时可能犯了一个错误characteristic。我假设您希望拥有一个可以读取、写入和设置通知的特性 - 在这种情况下它看起来像：

characteristic =
    new BluetoothGattCharacteristic(Constants.CHARACTERISTIC,
            BluetoothGattCharacteristic.PROPERTY_READ | BluetoothGattCharacteristic.PROPERTY_WRITE | BluetoothGattCharacteristic.PROPERTY_NOTIFY,
            BluetoothGattCharacteristic.PERMISSION_READ | BluetoothGattCharacteristic.PERMISSION_WRITE);

编辑- 请记住，如果中央请求打开通知，它会尝试写入客户端特征配置描述符。除非是带有设置的请求，NO_RESPONSE否则中央会期待响应。

正确的解决方案是添加回调并向onDescriptorWriteRequest中央发送响应：

BluetoothGattServerCallback serverCallback = new BluetoothGattServerCallback() {
    // (...)

    @Override
    public void onDescriptorWriteRequest(BluetoothDevice device, int requestId, BluetoothGattDescriptor descriptor,
                                         boolean preparedWrite, boolean responseNeeded, int offset, byte[] value) {
        super.onDescriptorWriteRequest(device, requestId, descriptor, preparedWrite, responseNeeded, offset, value);

        // validate if the request is exactly what you expect if needed
        bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, value);
    }

    // (...)
};

潜在的解决方法

一些中国制造商不符合蓝牙核心规范，并且在发送通知的特性下没有 CCC 描述符。如果您能够在不设置 CCC 的情况下获得通知，那么您可以使用兼容模式，RxBleConnection.setupNotifications(characteristic, NotificationSetupMode.COMPAT)尽管不鼓励这样做，并且应该对配置进行适当的修复。