- Qt 6.9
- Qt Bluetooth
- C++ Classes
- QBluetoothLocalDevice
- Qt 6.9.0 Reference Documentation

# QBluetoothLocalDevice Class

The QBluetoothLocalDevice class enables access to the local Bluetooth device. More...

Header: | `#include <QBluetoothLocalDevice>`
qmake: | `QT += bluetooth`
Inherits: | QObject

- List of all members, including inherited members

## Public Types

enum | Error { NoError, PairingError, MissingPermissionsError, UnknownError }
enum | HostMode { HostPoweredOff, HostConnectable, HostDiscoverable, HostDiscoverableLimitedInquiry }
enum | Pairing { Unpaired, Paired, AuthorizedPaired }

## Public Functions

| QBluetoothLocalDevice(QObject *parent = nullptr)
| QBluetoothLocalDevice(const QBluetoothAddress &address, QObject *parent = 0)
virtual | ~QBluetoothLocalDevice()
QBluetoothAddress | address() const
QList<QBluetoothAddress> | connectedDevices() const
QBluetoothLocalDevice::HostMode | hostMode() const
bool | isValid() const
QString | name() const
QBluetoothLocalDevice::Pairing | pairingStatus(const QBluetoothAddress &address) const
void | powerOn()
void | requestPairing(const QBluetoothAddress &address, QBluetoothLocalDevice::Pairing pairing)
void | setHostMode(QBluetoothLocalDevice::HostMode mode)

## Signals

void | deviceConnected(const QBluetoothAddress &address)
void | deviceDisconnected(const QBluetoothAddress &address)
`(since 6.2)` void | errorOccurred(QBluetoothLocalDevice::Error error)
void | hostModeStateChanged(QBluetoothLocalDevice::HostMode state)
void | pairingFinished(const QBluetoothAddress &address, QBluetoothLocalDevice::Pairing pairing)

## Static Public Members

QList<QBluetoothHostInfo> | allDevices()

## Detailed Description

QBluetoothLocalDevice provides functions for getting and setting the state of local Bluetooth devices.

On iOS, this class cannot be used because the platform does not expose any data or API which may provide information on the local Bluetooth device.

## Member Type Documentation

### enum QBluetoothLocalDevice::Error

This enum describes errors that maybe returned

Constant | Value | Description
--- | --- | ---
`QBluetoothLocalDevice::NoError` | `0` | No known error
`QBluetoothLocalDevice::PairingError` | `1` | Error in pairing
`QBluetoothLocalDevice::MissingPermissionsError (since Qt 6.4)` | `2` | The operating system requests permissions which were not granted by the user.
`QBluetoothLocalDevice::UnknownError` | `100` | Unknown error

### enum QBluetoothLocalDevice::HostMode

This enum describes the most of the local Bluetooth device.

Constant | Value | Description
--- | --- | ---
`QBluetoothLocalDevice::HostPoweredOff` | `0` | Power off the device
`QBluetoothLocalDevice::HostConnectable` | `1` | Remote Bluetooth devices can connect to the local Bluetooth device if they have previously been paired with it or otherwise know its address. This powers up the device if it was powered off.
`QBluetoothLocalDevice::HostDiscoverable` | `2` | Remote Bluetooth devices can discover the presence of the local Bluetooth device. The device will also be connectable, and powered on. On Android, this mode can only be active for a maximum of 5 minutes.
`QBluetoothLocalDevice::HostDiscoverableLimitedInquiry` | `3` | Remote Bluetooth devices can discover the presence of the local Bluetooth device when performing a limited inquiry. This should be used for locating services that are only made discoverable for a limited period of time. This can speed up discovery between gaming devices, as service discovery can be skipped on devices not in LimitedInquiry mode. In this mode, the device will be connectable and powered on, if required. This mode is is not supported on Android.

Note: On macOS, it is not possible to set the hostMode(). The reported host modes are limited to HostPoweredOff and HostConnectable.

Note: On Windows, it is not possible to set the hostMode() to HostDiscoverable or HostDiscoverableLimitedInquiry. Using these modes is equivalent to HostConnectable.

Note: Starting from Android 13 (API level 33) the HostPoweredOff state relies on non-public Android API as the public one has been deprecated, see (disable()). This may change in a future version of Android.

Note: At least on Android 12 the device's Bluetooth visibility setting may dictate the result of setting either HostDiscoverable or HostConnectable. For example if the visibility is set off, it may not be possible to enter the HostDiscoverable mode, but HostConnectable will be used instead. This may change in future version of Android.

### enum QBluetoothLocalDevice::Pairing

This enum describes the pairing state between the two Bluetooth devices.

Constant | Value | Description
--- | --- | ---
`QBluetoothLocalDevice::Unpaired` | `0` | The Bluetooth devices are not paired.
`QBluetoothLocalDevice::Paired` | `1` | The Bluetooth devices are paired. The system will prompt the user for authorization when the remote device initiates a connection to the local device.
`QBluetoothLocalDevice::AuthorizedPaired` | `2` | The Bluetooth devices are paired. The system will not prompt the user for authorization when the remote device initiates a connection to the local device.

## Member Function Documentation

### `[explicit]` QBluetoothLocalDevice::QBluetoothLocalDevice(QObject *parent = nullptr)

Constructs a QBluetoothLocalDevice with parent.

Note: Starting from Android 12 (API level 31), the construction of this class requires bluetooth runtime permissions (BLUETOOTH_SCAN and BLUETOOTH_CONNECT). If the permissions are not granted, the device will not be valid.

See also isValid().

### `[explicit]` QBluetoothLocalDevice::QBluetoothLocalDevice(const QBluetoothAddress &address, QObject *parent = 0)

Construct new QBluetoothLocalDevice for address. If address is default constructed the resulting local device selects the local default device.

Note: Starting from Android 12 (API level 31), the construction of this class requires bluetooth runtime permissions (BLUETOOTH_SCAN and BLUETOOTH_CONNECT). If the permissions are not granted, the device will not be valid.

See also isValid().

### `[virtual noexcept]` QBluetoothLocalDevice::~QBluetoothLocalDevice()

Destroys the QBluetoothLocalDevice.

### QBluetoothAddress QBluetoothLocalDevice::address() const

Returns the MAC address of this Bluetooth device.

Note: On Android, this function always returns the constant value `02:00:00:00:00:00` as local address starting with Android 6.0. The programmatic access to the device's local MAC address was removed.

### `[static]` QList<QBluetoothHostInfo> QBluetoothLocalDevice::allDevices()

Returns a list of all available local Bluetooth devices. On macOS, there is only the "default" local device.

### QList<QBluetoothAddress> QBluetoothLocalDevice::connectedDevices() const

Returns the list of connected devices. This list is different from the list of currently paired devices.

On Android and macOS, it is not possible to retrieve a list of connected devices. It is only possible to listen to (dis)connect changes. For convenience, this class monitors all connect and disconnect events since its instanciation and returns the current list when calling this function. Therefore it is possible that this function returns an empty list shortly after creating an instance.

See also deviceConnected() and deviceDisconnected().

### `[signal]` void QBluetoothLocalDevice::deviceConnected(const QBluetoothAddress &address)

This signal is emitted when the local device establishes a connection to a remote device with address.

See also deviceDisconnected() and connectedDevices().

### `[signal]` void QBluetoothLocalDevice::deviceDisconnected(const QBluetoothAddress &address)

This signal is emitted when the local device disconnects from a remote Bluetooth device with address.

See also deviceConnected() and connectedDevices().

### `[signal, since 6.2]` void QBluetoothLocalDevice::errorOccurred(QBluetoothLocalDevice::Error error)

Signal emitted if there's an exceptional error while pairing.

This function was introduced in Qt 6.2.

### QBluetoothLocalDevice::HostMode QBluetoothLocalDevice::hostMode() const

Returns the current host mode of this local Bluetooth device. On macOS, it is either HostPoweredOff or HostConnectable.

See also setHostMode().

### `[signal]` void QBluetoothLocalDevice::hostModeStateChanged(QBluetoothLocalDevice::HostMode state)

The state of the host has transitioned to a different HostMode.

### bool QBluetoothLocalDevice::isValid() const

Returns `true` if the QBluetoothLocalDevice represents an available local Bluetooth device; otherwise return false.

If the local Bluetooth adapter represented by an instance of this class is removed from the system (e.g. removal of the underlying Bluetooth dongle) then this instance will become invalid. An already invalid QBluetoothLocalDevice instance remains invalid even if the same Bluetooth adapter is returned to the system.

Note: Starting from Android 12 (API level 31), the construction of this class requires bluetooth runtime permissions (BLUETOOTH_SCAN and BLUETOOTH_CONNECT). If the permissions are not granted, the device will not be valid.

See also allDevices().

### QString QBluetoothLocalDevice::name() const

Returns the name assgined by the user to this Bluetooth device.

### `[signal]` void QBluetoothLocalDevice::pairingFinished(const QBluetoothAddress &address, QBluetoothLocalDevice::Pairing pairing)

Pairing or unpairing has completed with address. Current pairing status is in pairing. If the pairing request was not successful, this signal will not be emitted. The errorOccurred() signal is emitted if the pairing request failed. The signal is only ever emitted for pairing requests which have previously requested by calling requestPairing() of the current object instance.

### QBluetoothLocalDevice::Pairing QBluetoothLocalDevice::pairingStatus(const QBluetoothAddress &address) const

Returns the current bluetooth pairing status of address, if it's unpaired, paired, or paired and authorized.

### void QBluetoothLocalDevice::powerOn()

Powers on the device after returning it to the hostMode() state, if it was powered off.

Note: Due to varying security policies on the supported platforms, this method may have differing behaviors on the various platforms. For example the system may ask the user for confirmation before turning Bluetooth on or off. On macOS it is not possible to power on/off Bluetooth. Please refer to the platform specific Bluetooth documentation for details.

### void QBluetoothLocalDevice::requestPairing(const QBluetoothAddress &address, QBluetoothLocalDevice::Pairing pairing)

Set the pairing status with address. The results are returned by the signal, pairingFinished().

On Android and macOS, AuthorizedPaired is not possible and will have the same behavior as Paired. On Windows the exact pairing mode decision is up to the operating system.

On macOS, it is not possible to unpair a device. If Unpaired is requested, pairingFinished() is immediately emitted although the device remains paired. It is possible to request the pairing for a previously unpaired device. In addition AuthorizedPaired has the same behavior as Paired.

Caution: creating a pairing may take minutes, and may require the user to acknowledge.

### void QBluetoothLocalDevice::setHostMode(QBluetoothLocalDevice::HostMode mode)

Sets the host mode of this local Bluetooth device to mode.

Some transitions such as turning the device on or off may take some time. Therefore subsequent calls should only be made once the hostModeStateChanged() signal has concluded the previous request. If this is ignored the result of such a series of calls is not well defined.

Note: Due to varying security policies on the supported platforms, this method may have differing behaviors on the various platforms. For example the system may ask the user for confirmation before turning Bluetooth on or off and not all host modes may be supported. On macOS, it is not possbile to programmatically change the hostMode(). A user can only switch Bluetooth on/off in the System Preferences. On Windows this method must be called from the UI thread because it might require user confirmation. Please refer to the platform specific Bluetooth documentation for details.

See also hostMode().