bluetooth-index.qdoc

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// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
\page qtbluetooth-index.html
\title Qt Bluetooth
\brief Qt Bluetooth enables connectivity between Bluetooth enabled devices.
\ingroup technology-apis
 
The Bluetooth API provides connectivity between Bluetooth enabled devices.
 
Currently, the API is supported on the following platforms:
 
\table
\header
    \li API Feature
    \li \l {Qt for Android}{Android}
    \li \l {Qt for HarmonyOS}{HarmonyOS}
    \li \l {Qt for iOS}{iOS}
    \li \l {Qt for Linux}{Linux (BlueZ 5.x)}
    \li \l {Qt for macOS}{\macos}
    \li \l {Qt for Windows}{Windows}
\row
    \li Classic Bluetooth
    \li x
    \li x
    \li
    \li x
    \li x
    \li x
\row
    \li Bluetooth LE Central
    \li x
    \li
    \li x
    \li x
    \li x
    \li x
\row
    \li Bluetooth LE Peripheral
    \li x
    \li
    \li x
    \li x
    \li x
    \li
\endtable
 
\section1 Overview
 
Bluetooth is a short-range (less than 100 meters) wireless technology. It
has a data transfer rate of 2.1 Mbps, 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
\l {Bluetooth Low Energy Overview}{Bluetooth Low Energy Overview} section.
 
\section1 Using the Module
 
\include {module-use.qdocinc} {using the c++ api}
 
\section2 Building with CMake
 
\include {module-use.qdocinc} {building with cmake} {Bluetooth}
 
\section2 Building with qmake
 
\include {module-use.qdocinc} {building_with_qmake} {bluetooth}
 
\section1 Permissions
 
Starting from Qt 6.6, the Qt Bluetooth module uses new \l QPermission API
to handle \l {QBluetoothPermission}{Bluetooth} permissions. This means that Qt
itself no longer queries for these permissions, so this needs to be done
directly from the client application.
 
Please refer to the \l {Application Permissions} page for an example of how
to integrate the new \l QPermission API into the application.
 
\section1 Related Information
 
\section2 Building Qt Bluetooth
 
Even though the module can be built for all Qt platforms, the module is not
ported to all of them. Non-supported platforms employ a dummy backend that is
automatically selected when the platform is not supported. The dummy backend
reports appropriate error messages and values, which enables you 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.
 
\section3 Linux Specific
 
Since Qt 6.5 the Linux peripheral support has two backend alternatives:
BlueZ DBus and Bluetooth Kernel API. The DBus backend is the default
backend since Qt 6.7.
 
BlueZ DBus is the newer BlueZ stack and possibly the eventual successor of the
older Kernel API. It is a bit more limited in terms of features, but in a
typical usage this should not matter. One notable benefit of using the DBus
backend is that the user process no longer needs to have the
\e CAP_NET_ADMIN capability (for example by running as \c root user).
 
The DBus backend requires BlueZ version 5.56 or higher, and that it provides
the needed DBus APIs. If these requirements are not met, Qt automatically
falls back to the Bluetooth Kernel API backend.
 
The older kernel backend can also be selected manually by setting the
\e QT_BLUETOOTH_USE_KERNEL_PERIPHERAL environment variable.
 
\section3 \macos Specific
The Bluetooth API on \macos requires a certain type of event dispatcher
that in Qt causes a dependency to \l QGuiApplication. However, you can set the
environment variable \c {QT_EVENT_DISPATCHER_CORE_FOUNDATION=1} to circumvent
this issue.
 
Applications that don't use Classic Bluetooth will find a subset of QtBluetooth
is available, as CoreBluetooth (Bluetooth LE) don't require \l QApplication or
\l QGuiApplication.
 
\section2 Articles and Guides
\list
    \li \l {Qt Bluetooth Overview}{Classic Bluetooth Overview}
    \li \l {Bluetooth Low Energy Overview}
\endlist
 
\section2 Reference
\list
    \li \l {Qt Bluetooth C++ Classes}{C++ Classes}
\endlist
 
\section2 Logging Categories
 
The \l QtBluetooth module exports the following
\l {Configuring Categories}{logging categories}:
 
\table
\header
    \li Logging Category
    \li Description
\row
    \li qt.bluetooth
    \li Enables logging of cross platform code path in QtBluetooth
\row
    \li qt.bluetooth.android
    \li Enables logging of the \l {Qt for Android} {Android} implementation
\row
    \li qt.bluetooth.bluez
    \li Enables logging of the BLuez/Linux implementation
\row
    \li qt.bluetooth.ios
    \li Enables logging of the \l {Qt for iOS} {iOS} implementation
\row
    \li qt.bluetooth.ohos
    \li Enables logging of the \l {Qt for HarmonyOS} {HarmonyOS} implementation
\row
    \li qt.bluetooth.osx
    \li Enables logging of the \l {Qt for macOS} {macOS} implementation
\row
    \li qt.bluetooth.windows
    \li Enables logging of the \l {Qt for Windows} {Windows} implementation
\endtable
 
Logging categories enable additional warning and debug output for QtBluetooth.
More detailed information about logging is found in \l QLoggingCategory. A
quick way to enable all QtBluetooth logging is to add the following line to the
\c main() function:
 
\code
    QLoggingCategory::setFilterRules(QStringLiteral("qt.bluetooth* = true"));
\endcode
 
\section2 Examples
\list
    \li QML
    \list
        \li \l {heartrate-game}{Bluetooth Low Energy Heart Rate Game}
        \li \l {heartrate-server}{Bluetooth Low Energy Heart Rate Server}
        \li \l {lowenergyscanner}{Bluetooth Low Energy Scanner}
    \endlist
    \li C++
    \list
        \li \l {btchat}{Bluetooth Chat}
    \endlist
\endlist
 
\section1 Module Evolution
 
\l{Changes to Qt Bluetooth} lists important changes in the module
API and functionality that were done for the Qt 6 series of Qt.
 
\section1 Licenses and Attributions
 
Qt Bluetooth is available under commercial licenses from \l{The Qt Company}.
In addition, it is available under the
\l{GNU Lesser General Public License, version 3}, or
the \l{GNU General Public License, version 2}.
See \l{Qt Licensing} for further details.
 
On Linux, Qt Bluetooth uses a separate executable, \c sdpscanner,
to integrate with the official Linux bluetooth protocol stack
BlueZ. BlueZ is available under the \l{GNU General Public License,
version 2}.
 
\annotatedlist attributions-qtbluetooth
*/