- Qt 5.15
- Qt Bluetooth
- C++ Classes
- QBluetoothServer
- Qt 5.15.18 Reference Documentation

# QBluetoothServer Class

The QBluetoothServer class uses the RFCOMM or L2cap protocol to communicate with a Bluetooth device. More...

Header: | #include <QBluetoothServer>
qmake: | QT += bluetooth
Since: | Qt 5.2
Inherits: | QObject

This class was introduced in Qt 5.2.

- List of all members, including inherited members

## Public Types

enum | Error { NoError, UnknownError, PoweredOffError, InputOutputError, ServiceAlreadyRegisteredError, UnsupportedProtocolError }

## Public Functions

| QBluetoothServer(QBluetoothServiceInfo::Protocol serverType, QObject *parent = nullptr)
virtual | ~QBluetoothServer()
void | close()
Error | error() const
bool | hasPendingConnections() const
bool | isListening() const
bool | listen(const QBluetoothAddress &address = QBluetoothAddress(), quint16 port = 0)
QBluetoothServiceInfo | listen(const QBluetoothUuid &uuid, const QString &serviceName = QString())
int | maxPendingConnections() const
QBluetoothSocket * | nextPendingConnection()
QBluetooth::SecurityFlags | securityFlags() const
QBluetoothAddress | serverAddress() const
quint16 | serverPort() const
QBluetoothServiceInfo::Protocol | serverType() const
void | setMaxPendingConnections(int numConnections)
void | setSecurityFlags(QBluetooth::SecurityFlags security)

## Signals

void | error(QBluetoothServer::Error error)
void | newConnection()

## Detailed Description

QBluetoothServer is used to implement Bluetooth services over RFCOMM or L2cap.

Start listening for incoming connections with listen(). Wait till the newConnection() signal is emitted when a new connection is established, and call nextPendingConnection() to get a QBluetoothSocket for the new connection.

To enable other devices to find your service, create a QBluetoothServiceInfo with the applicable attributes for your service and register it using QBluetoothServiceInfo::registerService(). Call serverPort() to get the channel number that is being used.

If the QBluetoothServiceInfo::Protocol is not supported by a platform, listen() will return `false`. Android and WinRT only support RFCOMM for example.

On iOS, this class cannot be used because the platform does not expose an API which may permit access to QBluetoothServer related features.

See also QBluetoothServiceInfo and QBluetoothSocket.

## Member Type Documentation

### enum QBluetoothServer::Error

This enum describes Bluetooth server error types.

Constant | Value | Description
--- | --- | ---
`QBluetoothServer::NoError` | `0` | No error.
`QBluetoothServer::UnknownError` | `1` | An unknown error occurred.
`QBluetoothServer::PoweredOffError` | `2` | The Bluetooth adapter is powered off.
`QBluetoothServer::InputOutputError` | `3` | An input output error occurred.
`QBluetoothServer::ServiceAlreadyRegisteredError` | `4` | The service or port was already registered
`QBluetoothServer::UnsupportedProtocolError` | `5` | The Protocol is not supported on this platform.

## Member Function Documentation

### QBluetoothServer::QBluetoothServer(QBluetoothServiceInfo::Protocol serverType, QObject *parent = nullptr)

Constructs a bluetooth server with parent and serverType.

### `[signal]` void QBluetoothServer::error(QBluetoothServer::Error error)

This signal is emitted when an error occurs.

Note: Signal error is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

     connect(bluetoothServer, QOverload<QBluetoothServer::Error>::of(&QBluetoothServer::error),
         [=](QBluetoothServer::Error error){ /* ... */ });

See also error() and QBluetoothServer::Error.

### `[signal]` void QBluetoothServer::newConnection()

This signal is emitted when a new connection is available.

The connected slot should call nextPendingConnection() to get a QBluetoothSocket object to send and receive data over the connection.

See also nextPendingConnection() and hasPendingConnections().

### `[virtual]` QBluetoothServer::~QBluetoothServer()

Destroys the bluetooth server.

### void QBluetoothServer::close()

Closes and resets the listening socket. Any already established QBluetoothSocket continues to operate and must be separately closed.

### Error QBluetoothServer::error() const

Returns the last error of the QBluetoothServer.

### bool QBluetoothServer::hasPendingConnections() const

Returns true if a connection is pending, otherwise false.

### bool QBluetoothServer::isListening() const

Returns true if the server is listening for incoming connections, otherwise false.

### bool QBluetoothServer::listen(const QBluetoothAddress &address = QBluetoothAddress(), quint16 port = 0)

Start listening for incoming connections to address on port. address must be a local Bluetooth adapter address and port must be larger than zero and not be taken already by another Bluetooth server object. It is recommended to avoid setting a port number to enable the system to automatically choose a port.

Returns `true` if the operation succeeded and the server is listening for incoming connections, otherwise returns `false`.

If the server object is already listening for incoming connections this function always returns `false`. close() should be called before calling this function.

See also isListening() and newConnection().

### QBluetoothServiceInfo QBluetoothServer::listen(const QBluetoothUuid &uuid, const QString &serviceName = QString())

Convenience function for registering an SPP service with uuid and serviceName. Because this function already registers the service, the QBluetoothServiceInfo object which is returned can not be changed any more. To shutdown the server later on it is required to call QBluetoothServiceInfo::unregisterService() and close() on this server object.

Returns a registered QBluetoothServiceInfo instance if successful otherwise an invalid QBluetoothServiceInfo. This function always assumes that the default Bluetooth adapter should be used.

If the server object is already listening for incoming connections this function returns an invalid QBluetoothServiceInfo.

For an RFCOMM server this function is equivalent to following code snippet.

         QBluetoothServiceInfo serviceInfo;
         serviceInfo.setAttribute(QBluetoothServiceInfo::ServiceName, serviceName);
         QBluetoothServiceInfo::Sequence browseSequence;
         browseSequence << QVariant::fromValue(QBluetoothUuid(QBluetoothUuid::PublicBrowseGroup));
         serviceInfo.setAttribute(QBluetoothServiceInfo::BrowseGroupList,
                                  browseSequence);

         QBluetoothServiceInfo::Sequence profileSequence;
         QBluetoothServiceInfo::Sequence classId;
         classId << QVariant::fromValue(QBluetoothUuid(QBluetoothUuid::SerialPort));
         classId << QVariant::fromValue(quint16(0x100));
         profileSequence.append(QVariant::fromValue(classId));
         serviceInfo.setAttribute(QBluetoothServiceInfo::BluetoothProfileDescriptorList,
                                  profileSequence);

         classId.clear();
         //Android requires custom uuid to be set as service class
         classId << QVariant::fromValue(uuid);
         classId << QVariant::fromValue(QBluetoothUuid(QBluetoothUuid::SerialPort));
         serviceInfo.setAttribute(QBluetoothServiceInfo::ServiceClassIds, classId);
         serviceInfo.setServiceUuid(uuid);

         QBluetoothServiceInfo::Sequence protocolDescriptorList;
         QBluetoothServiceInfo::Sequence protocol;
         protocol << QVariant::fromValue(QBluetoothUuid(QBluetoothUuid::L2cap));
         if (d->serverType == QBluetoothServiceInfo::L2capProtocol)
             protocol << QVariant::fromValue(serverPort());
         protocolDescriptorList.append(QVariant::fromValue(protocol));
         protocol.clear();
         protocol << QVariant::fromValue(QBluetoothUuid(QBluetoothUuid::Rfcomm))
                  << QVariant::fromValue(quint8(serverPort()));
         protocolDescriptorList.append(QVariant::fromValue(protocol));
         serviceInfo.setAttribute(QBluetoothServiceInfo::ProtocolDescriptorList,
                                  protocolDescriptorList);
         bool result = serviceInfo.registerService();

See also isListening(), newConnection(), and listen().

### int QBluetoothServer::maxPendingConnections() const

Returns the maximum number of pending connections.

See also setMaxPendingConnections().

### QBluetoothSocket *QBluetoothServer::nextPendingConnection()

Returns a pointer to the QBluetoothSocket for the next pending connection. It is the callers responsibility to delete the pointer.

### QBluetooth::SecurityFlags QBluetoothServer::securityFlags() const

Returns the Bluetooth security flags.

See also setSecurityFlags().

### QBluetoothAddress QBluetoothServer::serverAddress() const

Returns the server address.

### quint16 QBluetoothServer::serverPort() const

Returns the server port number.

### QBluetoothServiceInfo::Protocol QBluetoothServer::serverType() const

Returns the type of the QBluetoothServer.

### void QBluetoothServer::setMaxPendingConnections(int numConnections)

Sets the maximum number of pending connections to numConnections. If the number of pending sockets exceeds this limit new sockets will be rejected.

See also maxPendingConnections().

### void QBluetoothServer::setSecurityFlags(QBluetooth::SecurityFlags security)

Sets the Bluetooth security flags to security. This function must be called before calling listen(). The Bluetooth link will always be encrypted when using Bluetooth 2.1 devices as encryption is mandatory.

Android only supports two levels of security (secure and non-secure). If this flag is set to QBluetooth::NoSecurity the server object will not employ any authentication or encryption. Any other security flag combination will trigger a secure Bluetooth connection.

On macOS, security flags are not supported and will be ignored.

See also securityFlags().