/**************************************************************************** ** ** Copyright (C) 2016 The Qt Company Ltd. ** Copyright (C) 2016 Javier S. Pedro ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the QtBluetooth module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and The Qt Company. For licensing terms ** and conditions see https://www.qt.io/terms-conditions. For further ** information use the contact form at https://www.qt.io/contact-us. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 3 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL3 included in the ** packaging of this file. Please review the following information to ** ensure the GNU Lesser General Public License version 3 requirements ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 2.0 or (at your option) the GNU General ** Public license version 3 or any later version approved by the KDE Free ** Qt Foundation. The licenses are as published by the Free Software ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 ** included in the packaging of this file. Please review the following ** information to ensure the GNU General Public License requirements will ** be met: https://www.gnu.org/licenses/gpl-2.0.html and ** https://www.gnu.org/licenses/gpl-3.0.html. ** ** $QT_END_LICENSE$ ** ****************************************************************************/ #include #include #include #include #include "qlowenergycontrollerbase_p.h" #include "qlowenergyserviceprivate_p.h" #ifdef Q_OS_DARWIN #include "qlowenergycontroller_darwin_p.h" #endif // Q_OS_DARWIN QT_BEGIN_NAMESPACE /*! \class QLowEnergyService \inmodule QtBluetooth \brief The QLowEnergyService class represents an individual service on a Bluetooth Low Energy Device. \since 5.4 QLowEnergyService provides access to the details of Bluetooth Low Energy services. The class facilitates the discovery and publification of service details, permits reading and writing of the contained data and notifies about data changes. \section1 Service Structure A Bluetooth Low Energy peripheral device can contain multiple services. In turn each service may include further services. This class represents a single service of the peripheral device and is created via \l QLowEnergyController::createServiceObject(). The \l type() indicates whether this service is a primary (top-level) service or whether the service is part of another service. Each service may contain one or more characteristics and each characteristic may contain descriptors. The resulting structure may look like the following diagram: \image peripheral-structure.png Structure of a generic peripheral A characteristic is the principal information carrier. It has a \l {QLowEnergyCharacteristic::value()}{value()} and \l {QLowEnergyCharacteristic::value()}{properties()} describing the access permissions for the value. The general purpose of the contained descriptor is to further define the nature of the characteristic. For example, it might specify how the value is meant to be interpreted or whether it can notify the value consumer about value changes. \section1 Service Interaction Once a service object was created for the first time, its details are yet to be discovered. This is indicated by its current \l state() being \l DiscoveryRequired. It is only possible to retrieve the \l serviceUuid() and \l serviceName(). The discovery of its included services, characteristics and descriptors is triggered when calling \l discoverDetails(). During the discovery the \l state() transitions from \l DiscoveryRequired via \l DiscoveringServices to its final \l ServiceDiscovered state. This transition is advertised via the \l stateChanged() signal. Once the details are known, all of the contained characteristics, descriptors and included services are known and can be read or written. The values of characteristics and descriptors can be retrieved via \l QLowEnergyCharacteristic and \l QLowEnergyDescriptor, respectively. However, direct reading or writing of these attributes requires the service object. The \l readCharacteristic() function attempts to re-read the value of a characteristic. Although the initial service discovery may have obtained a value already this call may be required in cases where the characteristic value constantly changes without any notifications being provided. An example might be a time characteristic that provides a continuous value. If the read attempt is successful, the \l characteristicRead() signal is emitted. A failure to read the value triggers the \l CharacteristicReadError. The \l writeCharacteristic() function attempts to write a new value to the given characteristic. If the write attempt is successful, the \l characteristicWritten() signal is emitted. A failure to write triggers the \l CharacteristicWriteError. Reading and writing of descriptors follows the same pattern. Every attempt is made to read or write the value of a descriptor or characteristic on the hardware. This means that meta information such as \l QLowEnergyCharacteristic::properties() is generally ignored when reading and writing. As an example, it is possible to call \l writeCharacteristic() despite the characteristic being read-only based on its meta data description. The resulting write request is forwarded to the connected device and it is up to the device to respond to the potentially invalid request. In this case the result is the emission of the \l CharacteristicWriteError in response to the returned device error. This behavior simplifies interaction with devices which report wrong meta information. If it was not possible to forward the request to the remote device the \l OperationError is set. A potential reason could be that the to-be-written characteristic object does not even belong the current service. In summary, the two types of errors permit a quick distinction of local and remote error cases. All requests are serialised based on First-In First-Out principle. For example, issuing a second write request, before the previous write request has finished, is delayed until the first write request has finished. \note Currently, it is not possible to send signed write or reliable write requests. \target notifications In some cases the peripheral generates value updates which the central is interested in receiving. In order for a characteristic to support such notifications it must have the \l QLowEnergyCharacteristic::Notify or \l QLowEnergyCharacteristic::Indicate property and a descriptor of type \l QBluetoothUuid::ClientCharacteristicConfiguration. Provided those conditions are fulfilled notifications can be enabled as shown in the following code segment: \snippet doc_src_qtbluetooth.cpp enable_btle_notifications The example shows a battery level characteristic which updates the central on every value change. The notifications are provided via the \l characteristicChanged() signal. More details about this mechanism are provided by the \l {https://developer.bluetooth.org/gatt/descriptors/Pages/DescriptorViewer.aspx?u=org.bluetooth.descriptor.gatt.client_characteristic_configuration.xml}{Bluetooth Specification}. \section1 Service Data Sharing Each QLowEnergyService instance shares its internal states and information with other QLowEnergyService instance of the same service. If one instance initiates the discovery of the service details, all remaining instances automatically follow. Therefore the following snippet always works: \snippet doc_src_qtbluetooth.cpp data_share_qlowenergyservice Other operations such as calls to \l readCharacteristic(), \l readDescriptor(), \l writeCharacteristic(), \l writeDescriptor() or the invalidation of the service due to the related \l QLowEnergyController disconnecting from the device are shared the same way. \sa QLowEnergyController, QLowEnergyCharacteristic, QLowEnergyDescriptor */ /*! \enum QLowEnergyService::ServiceType This enum describes the type of the service. \value PrimaryService The service is a top-level/primary service. If this type flag is not set, the service is considered to be a secondary service. Each service may be included by another service which is indicated by IncludedService. \value IncludedService The service is included by another service. On some platforms, this flag cannot be determined until the service that includes the current service was discovered. */ /*! \enum QLowEnergyService::ServiceError This enum describes all possible error conditions during the service's existence. The \l error() function returns the last occurred error. \value NoError No error has occurred. \value OperationError An operation was attempted while the service was not ready. An example might be the attempt to write to the service while it was not yet in the \l ServiceDiscovered \l state() or the service is invalid due to a loss of connection to the peripheral device. \value CharacteristicReadError An attempt to read a characteristic value failed. For example, it might be triggered in response to a call to \l readCharacteristic(). This value was introduced by Qt 5.5. \value CharacteristicWriteError An attempt to write a new value to a characteristic failed. For example, it might be triggered when attempting to write to a read-only characteristic. \value DescriptorReadError An attempt to read a descriptor value failed. For example, it might be triggered in response to a call to \l readDescriptor(). This value was introduced by Qt 5.5. \value DescriptorWriteError An attempt to write a new value to a descriptor failed. For example, it might be triggered when attempting to write to a read-only descriptor. \value UnknownError An unknown error occurred when interacting with the service. This value was introduced by Qt 5.5. */ /*! \enum QLowEnergyService::ServiceState This enum describes the \l state() of the service object. \value InvalidService A service can become invalid when it looses the connection to the underlying device. Even though the connection may be lost it retains its last information. An invalid service cannot become valid anymore even if the connection to the device is re-established. \value DiscoveryRequired The service details are yet to be discovered by calling \l discoverDetails(). The only reliable pieces of information are its \l serviceUuid() and \l serviceName(). \value DiscoveringServices The service details are being discovered. \value ServiceDiscovered The service details have been discovered. \value LocalService The service is associated with a controller object in the \l{QLowEnergyController::PeripheralRole}{peripheral role}. Such service objects do not change their state. This value was introduced by Qt 5.7. */ /*! \enum QLowEnergyService::WriteMode This enum describes the mode to be used when writing a characteristic value. The characteristic advertises its supported write modes via its \l {QLowEnergyCharacteristic::properties()}{properties}. \value WriteWithResponse If a characteristic is written using this mode, the peripheral shall send a write confirmation. If the operation is successful, the confirmation is emitted via the \l characteristicWritten() signal. Otherwise the \l CharacteristicWriteError is emitted. A characteristic must have set the \l QLowEnergyCharacteristic::Write property to support this write mode. \value WriteWithoutResponse If a characteristic is written using this mode, the remote peripheral shall not send a write confirmation. The operation's success cannot be determined and the payload must not be longer than 20 bytes. A characteristic must have set the \l QLowEnergyCharacteristic::WriteNoResponse property to support this write mode. Its adavantage is a quicker write operation as it may happen in between other device interactions. \value WriteSigned If a characteristic is written using this mode, the remote peripheral shall not send a write confirmation. The operation's success cannot be determined and the payload must not be longer than 8 bytes. A bond must exist between the two devices and the link must not be encrypted. A characteristic must have set the \l QLowEnergyCharacteristic::WriteSigned property to support this write mode. This value was introduced in Qt 5.7 and is currently only supported on Android and on Linux with BlueZ 5 and a kernel version 3.7 or newer. */ /*! \fn void QLowEnergyService::stateChanged(QLowEnergyService::ServiceState newState) This signal is emitted when the service's state changes. The \a newState can also be retrieved via \l state(). \sa state() */ /*! \fn void QLowEnergyService::error(QLowEnergyService::ServiceError newError) This signal is emitted when an error occurrs. The \a newError parameter describes the error that occurred. */ /*! \fn void QLowEnergyService::characteristicRead(const QLowEnergyCharacteristic &characteristic, const QByteArray &value) This signal is emitted when the read request for \a characteristic successfully returned its \a value. The signal might be triggered by calling \l characteristicRead(). If the read operation is not successful, the \l error() signal is emitted using the \l CharacteristicReadError flag. \note This signal is only emitted for Central Role related use cases. \sa readCharacteristic() \since 5.5 */ /*! \fn void QLowEnergyService::characteristicWritten(const QLowEnergyCharacteristic &characteristic, const QByteArray &newValue) This signal is emitted when the value of \a characteristic is successfully changed to \a newValue. The change must have been triggered by calling \l writeCharacteristic(). If the write operation is not successful, the \l error() signal is emitted using the \l CharacteristicWriteError flag. The reception of the written signal can be considered as a sign that the target device received the to-be-written value and reports back the status of write request. \note If \l writeCharacteristic() is called using the \l WriteWithoutResponse mode, this signal and the \l error() are never emitted. \note This signal is only emitted for Central Role related use cases. \sa writeCharacteristic() */ /*! \fn void QLowEnergyService::characteristicChanged(const QLowEnergyCharacteristic &characteristic, const QByteArray &newValue) If the associated controller object is in the \l {QLowEnergyController::CentralRole}{central} role, this signal is emitted when the value of \a characteristic is changed by an event on the peripheral/device side. In that case, the signal emission implies that change notifications must have been activated via the characteristic's \l {QBluetoothUuid::ClientCharacteristicConfiguration}{ClientCharacteristicConfiguration} descriptor prior to the change event on the peripheral. More details on how this might be done can be found further \l{notifications}{above}. If the controller is in the \l {QLowEnergyController::PeripheralRole}{peripheral} role, that is, the service object was created via \l QLowEnergyController::addService, the signal is emitted when a GATT client has written the value of the characteristic using a write request or command. The \a newValue parameter contains the updated value of the \a characteristic. */ /*! \fn void QLowEnergyService::descriptorRead(const QLowEnergyDescriptor &descriptor, const QByteArray &value) This signal is emitted when the read request for \a descriptor successfully returned its \a value. The signal might be triggered by calling \l descriptorRead(). If the read operation is not successful, the \l error() signal is emitted using the \l DescriptorReadError flag. \note This signal is only emitted for Central Role related use cases. \sa readDescriptor() \since 5.5 */ /*! \fn void QLowEnergyService::descriptorWritten(const QLowEnergyDescriptor &descriptor, const QByteArray &newValue) This signal is emitted when the value of \a descriptor is successfully changed to \a newValue. If the associated controller object is in the \l {QLowEnergyController::CentralRole}{central} role, the change must have been caused by calling \l writeDescriptor(). Otherwise, the signal is the result of a write request or command from a GATT client to the respective descriptor. \sa writeDescriptor() */ /*! \internal QLowEnergyControllerPrivate creates instances of this class. The user gets access to class instances via \l QLowEnergyController::services(). */ QLowEnergyService::QLowEnergyService(QSharedPointer p, QObject *parent) : QObject(parent), d_ptr(p) { qRegisterMetaType(); qRegisterMetaType(); qRegisterMetaType(); qRegisterMetaType(); connect(p.data(), &QLowEnergyServicePrivate::error, this, QOverload::of(&QLowEnergyService::error)); connect(p.data(), &QLowEnergyServicePrivate::stateChanged, this, &QLowEnergyService::stateChanged); connect(p.data(), &QLowEnergyServicePrivate::characteristicChanged, this, &QLowEnergyService::characteristicChanged); connect(p.data(), &QLowEnergyServicePrivate::characteristicWritten, this, &QLowEnergyService::characteristicWritten); connect(p.data(), &QLowEnergyServicePrivate::descriptorWritten, this, &QLowEnergyService::descriptorWritten); connect(p.data(), &QLowEnergyServicePrivate::characteristicRead, this, &QLowEnergyService::characteristicRead); connect(p.data(), &QLowEnergyServicePrivate::descriptorRead, this, &QLowEnergyService::descriptorRead); } /*! Destroys the \l QLowEnergyService instance. */ QLowEnergyService::~QLowEnergyService() { } /*! Returns the UUIDs of all services which are included by the current service. The returned list is empty if this service instance's \l discoverDetails() was not yet called or there are no known characteristics. It is possible that an included service contains yet another service. Such second level includes have to be obtained via their relevant first level QLowEnergyService instance. Technically, this could create a circular dependency. \l {QLowEnergyController::createServiceObject()} should be used to obtain service instances for each of the UUIDs. \sa {QLowEnergyController::}{createServiceObject()} */ QList QLowEnergyService::includedServices() const { return d_ptr->includedServices; } /*! Returns the current state of the service. If the device's service was instantiated for the first time, the object's state is \l DiscoveryRequired. The state of all service objects which point to the same service on the peripheral device are always equal. This is caused by the shared nature of the internal object data. Therefore any service object instance created after the first one has a state equal to already existing instances. A service becomes invalid if the \l QLowEnergyController disconnects from the remote device. An invalid service retains its internal state at the time of the disconnect event. This implies that once the service details are discovered they can even be retrieved from an invalid service. This permits scenarios where the device connection is established, the service details are retrieved and the device immediately disconnected to permit the next device to connect to the peripheral device. However, under normal circumstances the connection should remain to avoid repeated discovery of services and their details. The discovery may take a while and the client can subscribe to ongoing change notifications. \sa stateChanged() */ QLowEnergyService::ServiceState QLowEnergyService::state() const { return d_ptr->state; } /*! Returns the type of the service. \note The type attribute cannot be relied upon until the service has reached the \l ServiceDiscovered state. This field is initialised with \l PrimaryService. \note On Android, it is not possible to determine whether a service is a primary or secondary service. Therefore all services have the \l PrimaryService flag set. */ QLowEnergyService::ServiceTypes QLowEnergyService::type() const { return d_ptr->type; } /*! Returns the matching characteristic for \a uuid; otherwise an invalid characteristic. The returned characteristic is invalid if this service instance's \l discoverDetails() was not yet called or there are no characteristics with a matching \a uuid. \sa characteristics() */ QLowEnergyCharacteristic QLowEnergyService::characteristic(const QBluetoothUuid &uuid) const { CharacteristicDataMap::const_iterator charIt = d_ptr->characteristicList.constBegin(); for ( ; charIt != d_ptr->characteristicList.constEnd(); ++charIt) { const QLowEnergyHandle charHandle = charIt.key(); const QLowEnergyServicePrivate::CharData &charDetails = charIt.value(); if (charDetails.uuid == uuid) return QLowEnergyCharacteristic(d_ptr, charHandle); } return QLowEnergyCharacteristic(); } /*! Returns all characteristics associated with this \c QLowEnergyService instance. The returned list is empty if this service instance's \l discoverDetails() was not yet called or there are no known characteristics. \sa characteristic(), state(), discoverDetails() */ QList QLowEnergyService::characteristics() const { QList results; QList handles = d_ptr->characteristicList.keys(); std::sort(handles.begin(), handles.end()); for (const QLowEnergyHandle &handle : qAsConst(handles)) { QLowEnergyCharacteristic characteristic(d_ptr, handle); results.append(characteristic); } return results; } /*! Returns the UUID of the service; otherwise a null UUID. */ QBluetoothUuid QLowEnergyService::serviceUuid() const { return d_ptr->uuid; } /*! Returns the name of the service; otherwise an empty string. The returned name can only be retrieved if \l serviceUuid() is a \l {https://developer.bluetooth.org/gatt/services/Pages/ServicesHome.aspx}{well-known UUID}. */ QString QLowEnergyService::serviceName() const { bool ok = false; quint16 clsId = d_ptr->uuid.toUInt16(&ok); if (ok) { QBluetoothUuid::ServiceClassUuid id = static_cast(clsId); const QString name = QBluetoothUuid::serviceClassToString(id); if (!name.isEmpty()) return name; } return qApp ? qApp->translate("QBluetoothServiceDiscoveryAgent", "Unknown Service") : QStringLiteral("Unknown Service"); } /*! Initiates the discovery of the services, characteristics and descriptors contained by the service. The discovery process is indicated via the \l stateChanged() signal. \sa state() */ void QLowEnergyService::discoverDetails() { Q_D(QLowEnergyService); if (!d->controller || d->state == QLowEnergyService::InvalidService) { d->setError(QLowEnergyService::OperationError); return; } if (d->state != QLowEnergyService::DiscoveryRequired) return; d->setState(QLowEnergyService::DiscoveringServices); d->controller->discoverServiceDetails(d->uuid); } /*! Returns the last occurred error or \l NoError. */ QLowEnergyService::ServiceError QLowEnergyService::error() const { return d_ptr->lastError; } /*! Returns \c true if \a characteristic belongs to this service; otherwise \c false. A characteristic belongs to a service if \l characteristics() contains the \a characteristic. */ bool QLowEnergyService::contains(const QLowEnergyCharacteristic &characteristic) const { if (characteristic.d_ptr.isNull() || !characteristic.data) return false; if (d_ptr == characteristic.d_ptr && d_ptr->characteristicList.contains(characteristic.attributeHandle())) { return true; } return false; } /*! Reads the value of \a characteristic. If the operation is successful, the \l characteristicRead() signal is emitted; otherwise the \l CharacteristicReadError is set. In general, a \a characteristic is readable, if its \l QLowEnergyCharacteristic::Read property is set. All descriptor and characteristic requests towards the same remote device are serialised. A queue is employed when issuing multiple requests at the same time. The queue does not eliminate duplicated read requests for the same characteristic. A characteristic can only be read if the service is in the \l ServiceDiscovered state and belongs to the service. If one of these conditions is not true the \l QLowEnergyService::OperationError is set. \note Calling this function despite \l QLowEnergyCharacteristic::properties() reporting a non-readable property always attempts to read the characteristic's value on the hardware. If the hardware returns with an error the \l CharacteristicReadError is set. \sa characteristicRead(), writeCharacteristic() \since 5.5 */ void QLowEnergyService::readCharacteristic( const QLowEnergyCharacteristic &characteristic) { Q_D(QLowEnergyService); if (d->controller == nullptr || state() != ServiceDiscovered || !contains(characteristic)) { d->setError(QLowEnergyService::OperationError); return; } d->controller->readCharacteristic(characteristic.d_ptr, characteristic.attributeHandle()); } /*! Writes \a newValue as value for the \a characteristic. The exact semantics depend on the role that the associated controller object is in. \b {Central role} The call results in a write request or command to a remote peripheral. If the operation is successful, the \l characteristicWritten() signal is emitted; otherwise the \l CharacteristicWriteError is set. Calling this function does not trigger the a \l characteristicChanged() signal unless the peripheral itself changes the value again after the current write request. The \a mode parameter determines whether the remote device should send a write confirmation. The to-be-written \a characteristic must support the relevant write mode. The characteristic's supported write modes are indicated by its \l QLowEnergyCharacteristic::Write and \l QLowEnergyCharacteristic::WriteNoResponse properties. All descriptor and characteristic write requests towards the same remote device are serialised. A queue is employed when issuing multiple write requests at the same time. The queue does not eliminate duplicated write requests for the same characteristic. For example, if the same descriptor is set to the value A and immediately afterwards to B, the two write request are executed in the given order. \note Currently, it is not possible to use signed or reliable writes as defined by the Bluetooth specification. A characteristic can only be written if this service is in the \l ServiceDiscovered state and belongs to the service. If one of these conditions is not true the \l QLowEnergyService::OperationError is set. \note Calling this function despite \l QLowEnergyCharacteristic::properties() reporting a non-writable property always attempts to write to the hardware. Similarly, a \l WriteWithoutResponse is sent to the hardware too although the characteristic may only support \l WriteWithResponse. If the hardware returns with an error the \l CharacteristicWriteError is set. \b {Peripheral role} The call results in the value of the characteristic getting updated in the local database. If a client is currently connected and it has enabled notifications or indications for the characteristic, the respective information will be sent. If a device has enabled notifications or indications for the characteristic and that device is currently not connected, but a bond exists between it and the local device, then the notification or indication will be sent on the next reconnection. If there is a constraint on the length of the characteristic value and \a newValue does not adhere to that constraint, the behavior is unspecified. \note The \a mode argument is ignored in peripheral mode. \sa QLowEnergyService::characteristicWritten(), QLowEnergyService::readCharacteristic() */ void QLowEnergyService::writeCharacteristic( const QLowEnergyCharacteristic &characteristic, const QByteArray &newValue, QLowEnergyService::WriteMode mode) { //TODO check behavior when writing to WriteSigned characteristic Q_D(QLowEnergyService); if (d->controller == nullptr || (d->controller->role == QLowEnergyController::CentralRole && state() != ServiceDiscovered) || !contains(characteristic)) { d->setError(QLowEnergyService::OperationError); return; } // don't write if properties don't permit it d->controller->writeCharacteristic(characteristic.d_ptr, characteristic.attributeHandle(), newValue, mode); } /*! Returns \c true if \a descriptor belongs to this service; otherwise \c false. */ bool QLowEnergyService::contains(const QLowEnergyDescriptor &descriptor) const { if (descriptor.d_ptr.isNull() || !descriptor.data) return false; const QLowEnergyHandle charHandle = descriptor.characteristicHandle(); if (!charHandle) return false; if (d_ptr == descriptor.d_ptr && d_ptr->characteristicList.contains(charHandle) && d_ptr->characteristicList[charHandle].descriptorList.contains(descriptor.handle())) { return true; } return false; } /*! Reads the value of \a descriptor. If the operation is successful, the \l descriptorRead() signal is emitted; otherwise the \l DescriptorReadError is set. All descriptor and characteristic requests towards the same remote device are serialised. A queue is employed when issuing multiple requests at the same time. The queue does not eliminate duplicated read requests for the same descriptor. A descriptor can only be read if the service is in the \l ServiceDiscovered state and the descriptor belongs to the service. If one of these conditions is not true the \l QLowEnergyService::OperationError is set. \sa descriptorRead(), writeDescriptor() \since 5.5 */ void QLowEnergyService::readDescriptor( const QLowEnergyDescriptor &descriptor) { Q_D(QLowEnergyService); if (d->controller == nullptr || state() != ServiceDiscovered || !contains(descriptor)) { d->setError(QLowEnergyService::OperationError); return; } d->controller->readDescriptor(descriptor.d_ptr, descriptor.characteristicHandle(), descriptor.handle()); } /*! Writes \a newValue as value for \a descriptor. The exact semantics depend on the role that the associated controller object is in. \b {Central role} A call to this function results in a write request to the remote device. If the operation is successful, the \l descriptorWritten() signal is emitted; otherwise the \l DescriptorWriteError is emitted. All descriptor and characteristic requests towards the same remote device are serialised. A queue is employed when issuing multiple write requests at the same time. The queue does not eliminate duplicated write requests for the same descriptor. For example, if the same descriptor is set to the value A and immediately afterwards to B, the two write request are executed in the given order. A descriptor can only be written if this service is in the \l ServiceDiscovered state, belongs to the service. If one of these conditions is not true the \l QLowEnergyService::OperationError is set. \b {Peripheral Role} The value is written to the local service database. If the contents of \a newValue are not valid for \a descriptor, the behavior is unspecified. \sa descriptorWritten(), readDescriptor() */ void QLowEnergyService::writeDescriptor(const QLowEnergyDescriptor &descriptor, const QByteArray &newValue) { Q_D(QLowEnergyService); if (d->controller == nullptr || (d->controller->role == QLowEnergyController::CentralRole && state() != ServiceDiscovered) || !contains(descriptor)) { d->setError(QLowEnergyService::OperationError); return; } #ifdef Q_OS_DARWIN if (descriptor.uuid() == QBluetoothUuid::ClientCharacteristicConfiguration) { // We have to identify a special case - ClientCharacteristicConfiguration // since with CoreBluetooth: // // "You cannot use this method to write the value of a client configuration descriptor // (represented by the CBUUIDClientCharacteristicConfigurationString constant), // which describes how notification or indications are configured for a // characteristic’s value with respect to a client. If you want to manage // notifications or indications for a characteristic’s value, you must // use the setNotifyValue:forCharacteristic: method instead." auto controller = static_cast(d->controller.data()); return controller->setNotifyValue(descriptor.d_ptr, descriptor.characteristicHandle(), newValue); } #endif // Q_OS_DARWIN d->controller->writeDescriptor(descriptor.d_ptr, descriptor.characteristicHandle(), descriptor.handle(), newValue); } QT_END_NAMESPACE