- Qt 6.12
- Qt Bluetooth
- Changes to Qt Bluetooth
- Qt 6.12.0 Reference Documentation

Bluetooth Low Energy Overview

# Changes to Qt Bluetooth

Qt 6 is a result of the conscious effort to make the framework more efficient and easy to use.

We try to maintain binary and source compatibility for all the public APIs in each release. But some changes were inevitable in an effort to make Qt a better framework.

In this topic we summarize those changes in QtBluetooth, and provide guidance to handle them.

## General

- qbluetoothglobal.h was removed. qtbluetoothglobal.h is the official header with the same purpose.
- Every usage of QVector has been replaced by QList.
- Win32 backend has been removed. There will not be a working Bluetooth backend when Qt is built with mingw.
- Since there is now only one Windows backend, the logging category qt.bluetooth.winrt was removed. The corresponding log messages are now in qt.bluetooth.windows.

## QBluetooth namespace

The enums QBluetooth::Security and QBluetooth::AttAccessConstraint have been changed to a scoped enums for improved type safety.

## QBluetoothDeviceDiscoveryAgent

QBluetoothDeviceDiscoveryAgent::inquiryType property and related setter/getter & enum were removed. The API element was never implemented and/or supported.

## QBluetoothDeviceInfo

- manufacturerData() returns a QMultiHash rather than QHash. Since Qt 6 QMultiHash is no longer derived from QHash.
- DataCompleteness was removed without replacement as the related API elements no longer served a purpose
- setServiceUuids(const QList<QBluetoothUuid>, DataCompleteness) was replaced by setServiceUuids(const QList<QBluetoothUuid> &uuids)
- DataCompleteness serviceUuidsCompleteness() const was removed without replacement.
- QList<QBluetoothUuid> serviceUuids(DataCompleteness *completeness = nullptr) const was replaced by QList<QBluetoothUuid> serviceUuids() const.

## QBluetoothLocalDevice

The pairing agent related API was removed without replacement. This includes pairingConfirmation(bool), pairingDisplayPinCode(..) & pairingDisplayConfirmation(..). Except for Android and BlueZ 4 there was never an implementation for it. Bluez 4 support was removed in Qt 6 and Android's implementation required unobtainable BLUETOOTH_PRIVILEGED for at least parts of the code.

## QLowEnergyService

Renamed ServiceState enum values:

- DiscoveryRequired becomes RemoteService
- DiscoveringService becomes RemoteServiceDiscovering
- ServiceDiscovered becomes RemoteServiceDiscovered

This change happens in anticipation that service discovery might become an optional step in the future.

## QBluetoothUuid

enums ProtocolUuid, ServiceClassUuid, CharacteristicType, and DescriptorType are now scoped enums. The usage of enum items has to be adapted in user code.

## QLowEnergyController

- Existing ctors and create*() functions with remote QBluetoothAddress parameters have been removed. QBluetoothAddress is not sufficient to indicate remote devices on Apple systems. It requires UUIDs to "name" devices. This can only be satisfied by QBluetoothDeviceInfo.
- Remaining QLowEnergyController ctors have been made private. The createPeripheral() and createCentral() functions should be used to obtain QLowEnergyController instances.

## QLowEnergyCharacteristic

- The new method clientCharacteristicConfiguration() has been introduced to conveniently obtain the Client Characteristic Configuration Descriptor.
- The constants CCCDDisable, CCCDEnableNotification, and CCCDEnableIndication have been introduced which hold the possible values for the Client Characteristic Configuration Descriptor.
- The handle() method is no longer part of the public Bluetooth LE interfaces. It's purpose as identifier for characteristics was replaced. The QLowEnergyCharacteristic instances itself serve as identifier.

## QLowEnergyDescriptor

The handle() method is no longer part of the public Bluetooth LE interfaces. It's purpose as identifier for descriptors was replaced. The QLowEnergyDescriptor instances itself serve as identifier.

## QBluetoothTransferManager

QBluetoothTransferManager, QBluetoothTransferRequest, and QBluetoothTransferReply have been removed without replacement.

## QBluetoothSocket

QBluetoothSocket::SocketState and QBluetoothSocket::SocketError are now scoped enums. The usage of enum items has to be adapted in user code.

## QML Interface

The QML interface has been removed because socket programming via QML is not advisable. QDeclarativeBluetoothService, QDeclarativeBluetoothSocket, and QDeclarativeBluetoothDiscoveryModel (in QML: BluetoothService, BluetoothSocket, and BluetoothDiscoveryModel) have been removed without replacement.

## "error" signals

The "error" signals in QBluetoothDeviceDiscoveryAgent, QBluetoothLocalDevice, QBluetoothServer, QBluetoothServiceDiscoveryAgent, QBluetoothSocket, QLowEnergyController, and QLowEnergyService have been renamed to "errorOccurred" to remove ambiguities between the "error" signal and the "error" getter.

Bluetooth Low Energy Overview