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Qt Bluetooth

The Bluetooth API provides connectivity between Bluetooth enabled devices.

Currently, the API is supported on the following platforms:

API Feature Android iOS Linux (BlueZ 4.x/5.x) macOS WinRT Win32
Classic Bluetooth x x x x
Bluetooth LE Central x x x x x
Bluetooth LE Peripheral x x x x
Bluetooth LE Advertisement & Scanning

Despite there not being a Win32 port yet, the WinRT backend is automatically used if the win32 target platform supports the required WinRT APIs. Minimal requirement is Windows 10 version 1507 with slightly improved service discovery since Windows 10 version 1607. Therefore Windows 7 and 8.x targets are excluded.

Overview

Bluetooth is a short-range (less than 100 meters) wireless technology. It has a reasonably high data transfer rate of 2.1 Mbit/s, which makes it ideal for transferring data between devices. Bluetooth connectivity is based on basic device management, such as scanning for devices, gathering information about them, and exchanging data between them.

Qt Bluetooth supports Bluetooth Low Energy development for client/central role use cases. Further details can be found in the Bluetooth Low Energy Overview section.

A new addition since the Qt Bluetooth 5.7 release covers support for Bluetooth Low Energy applications performing the peripheral/server role. This new API remains in Technology Preview.

Getting Started

To use the C++ library in your application, add the following configuration option to your .pro file:

QT += bluetooth

To use the classes of the module in your application you need the following import statement in your .qml file:

import QtBluetooth 5.2

Building Qt Bluetooth

Despite the fact that the module can be built for all Qt platforms, the module is not ported to all of them. Not supported platforms such as Windows desktop employ a fake or dummy backend which is automatically selected when the platform is not supported. The dummy backend reports appropriate error messages and values which allow the Qt Bluetooth developer to detect at runtime that the current platform is not supported. The dummy backend is also selected on Linux if BlueZ development headers are not found during build time or Qt was built without Qt D-Bus support.

The usage of the dummy backend is highlighted via an appropriate warning while building and running.

Guides

Reference

Logging Categories

The QtBluetooth module exports the following logging categories:

Logging Category Description
qt.bluetooth Enables logging of cross platform code path in QtBluetooth
qt.bluetooth.android Enables logging of the Android implementation
qt.bluetooth.bluez Enables logging of the BLuez/Linux implementation
qt.bluetooth.ios Enables logging of the iOS implementation
qt.bluetooth.osx Enables logging of the macOS implementation
qt.bluetooth.qml Enables logging of the QtBluetooth QML implementation
qt.bluetooth.winrt Enables logging of the WinRT implementation

Logging categories can be used to enable additional warning and debug output for QtBluetooth. More detailed information about logging can be found in QLoggingCategory. A quick way to enable all QtBluetooth logging is to add the following line to the main() function:

QLoggingCategory::setFilterRules(QStringLiteral("qt.bluetooth* = true"));

Examples

Licenses and Attributions

Qt Bluetooth is available under commercial licenses from The Qt Company. In addition, it is available under the GNU Lesser General Public License, version 3, or the GNU General Public License, version 2. See Qt Licensing for further details.

On Linux, Qt Bluetooth uses a separate executable, sdpscanner, to integrate with the official Linux bluetooth protocol stack BlueZ. BlueZ is available under the GNU General Public License, version 2.

BlueZ

GNU General Public License v2.0 only (This does not force user code to be GPL'ed. For more info see details.)