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# QDBusConnection Class Reference
[QtDBus module]

The QDBusConnection class represents a connection to the D-Bus bus daemon. More...

     #include <QDBusConnection>

This class was introduced in Qt 4.2.

- List of all members, including inherited members

### Public Types

- enum BusType { SessionBus, SystemBus, ActivationBus }
- enum RegisterOption { ExportAdaptors, ExportScriptableSlots, ExportScriptableSignals, ExportScriptableProperties, ..., ExportChildObjects }
- flags RegisterOptions
- enum UnregisterMode { UnregisterNode, UnregisterTree }

### Public Functions

- QDBusConnection ( const QString & name )
- QDBusConnection ( const QDBusConnection & other )
- ~QDBusConnection ()
- QString baseService () const
- QDBusMessage call ( const QDBusMessage & message, QDBus::CallMode mode = QDBus::Block, int timeout = -1 ) const
- bool callWithCallback ( const QDBusMessage & message, QObject * receiver, const char * returnMethod, const char * errorMethod, int timeout = -1 ) const
- bool callWithCallback ( const QDBusMessage & message, QObject * receiver, const char * returnMethod, int timeout = -1 ) const `(deprecated)`
- bool connect ( const QString & service, const QString & path, const QString & interface, const QString & name, QObject * receiver, const char * slot )
- bool connect ( const QString & service, const QString & path, const QString & interface, const QString & name, const QString & signature, QObject * receiver, const char * slot )
- bool disconnect ( const QString & service, const QString & path, const QString & interface, const QString & name, QObject * receiver, const char * slot )
- bool disconnect ( const QString & service, const QString & path, const QString & interface, const QString & name, const QString & signature, QObject * receiver, const char * slot )
- QDBusConnectionInterface * interface () const
- bool isConnected () const
- QDBusError lastError () const
- QObject * objectRegisteredAt ( const QString & path ) const
- bool registerObject ( const QString & path, QObject * object, RegisterOptions options = ExportAdaptors )
- bool registerService ( const QString & serviceName )
- bool send ( const QDBusMessage & message ) const
- void unregisterObject ( const QString & path, UnregisterMode mode = UnregisterNode )
- bool unregisterService ( const QString & serviceName )
- QDBusConnection & operator= ( const QDBusConnection & other )

### Static Public Members

- QDBusConnection connectToBus ( BusType type, const QString & name )
- QDBusConnection connectToBus ( const QString & address, const QString & name )
- void disconnectFromBus ( const QString & name )
- QDBusConnection sender ()
- QDBusConnection sessionBus ()
- QDBusConnection systemBus ()

### Related Non-Members

- QDBusConnection sessionBus ()
- QDBusConnection systemBus ()

## Detailed Description

The QDBusConnection class represents a connection to the D-Bus bus daemon.

This class is the initial point in a D-Bus session. Using it, you can get access to remote objects, interfaces; connect remote signals to your object's slots; register objects, etc.

D-Bus connections are created using the connectToBus() function, which opens a connection to the server daemon and does the initial handshaking, associating that connection with a name. Further attempts to connect using the same name will return the same connection.

The connection is then torn down using the disconnectFromBus() function.

As a convenience for the two most common connection types, the sessionBus() and systemBus() functions return open connections to the session server daemon and the system server daemon, respectively. Those connections are opened when first used and are closed when the QCoreApplication destructor is run.

D-Bus also supports peer-to-peer connections, without the need for a bus server daemon. Using this facility, two applications can talk to each other and exchange messages. This can be achieved by passing an address to connectToBus() function, which was opened by another D-Bus application using QDBusServer.

## Member Type Documentation

### enum QDBusConnection::BusType

Specifies the type of the bus connection. The valid bus types are:

Constant | Value | Description
--- | --- | ---
`QDBusConnection::SessionBus` | `0` | the session bus, associated with the running desktop session
`QDBusConnection::SystemBus` | `1` | the system bus, used to communicate with system-wide processes
`QDBusConnection::ActivationBus` | `2` | the activation bus, the "alias" for the bus that started the service

On the Session Bus, one can find other applications by the same user that are sharing the same desktop session (hence the name). On the System Bus, however, processes shared for the whole system are usually found.

### enum QDBusConnection::RegisterOption
flags QDBusConnection::RegisterOptions

Specifies the options for registering objects with the connection. The possible values are:

Constant | Value | Description
--- | --- | ---
`QDBusConnection::ExportAdaptors` | `0x01` | export the contents of adaptors found in this object
`QDBusConnection::ExportScriptableSlots` | `0x10` | export this object's scriptable slots
`QDBusConnection::ExportScriptableSignals` | `0x20` | export this object's scriptable signals
`QDBusConnection::ExportScriptableProperties` | `0x40` | export this object's scriptable properties
`QDBusConnection::ExportScriptableContents` | `0xf0` | shorthand form for ExportScriptableSlots | ExportScriptableSignals | ExportScriptableProperties
`QDBusConnection::ExportNonScriptableSlots` | `0x100` | export this object's non-scriptable slots
`QDBusConnection::ExportNonScriptableSignals` | `0x200` | export this object's non-scriptable signals
`QDBusConnection::ExportNonScriptableProperties` | `0x400` | export this object's non-scriptable properties
`QDBusConnection::ExportNonScriptableContents` | `0xf00` | shorthand form for ExportNonScriptableSlots | ExportNonScriptableSignals | ExportNonScriptableProperties
`QDBusConnection::ExportAllSlots` | `ExportScriptableSlots | ExportNonScriptableSlots` | export all of this object's slots
`QDBusConnection::ExportAllSignals` | `ExportScriptableSignals | ExportNonScriptableSignals` | export all of this object's signals
`QDBusConnection::ExportAllProperties` | `ExportScriptableProperties | ExportNonScriptableProperties` | export all of this object's properties
`QDBusConnection::ExportAllContents` | `ExportScriptableContents | ExportNonScriptableContents` | export all of this object's contents
`QDBusConnection::ExportChildObjects` | `0x1000` | export this object's child objects

The RegisterOptions type is a typedef for QFlags<RegisterOption>. It stores an OR combination of RegisterOption values.

See also registerObject(), QDBusAbstractAdaptor, and Using adaptors.

### enum QDBusConnection::UnregisterMode

The mode for unregistering an object path:

Constant | Value | Description
--- | --- | ---
`QDBusConnection::UnregisterNode` | `0` | unregister this node only: do not unregister child objects
`QDBusConnection::UnregisterTree` | `1` | unregister this node and all its sub-tree

Note, however, if this object was registered with the ExportChildObjects option, UnregisterNode will unregister the child objects too.

## Member Function Documentation

### QDBusConnection::QDBusConnection ( const QString & name )

Creates a QDBusConnection object attached to the connection with name name.

This does not open the connection. You have to call connectToBus() to open it.

### QDBusConnection::QDBusConnection ( const QDBusConnection & other )

Creates a copy of the other connection.

### QDBusConnection::~QDBusConnection ()

Disposes of this object. This does not close the connection: you have to call disconnectFromBus() to do that.

### QString QDBusConnection::baseService () const

Returns the unique connection name for this connection, if this QDBusConnection object is connected, or an empty QString otherwise.

A Unique Connection Name is a string in the form ":x.xxx" (where x are decimal digits) that is assigned by the D-Bus server daemon upon connection. It uniquely identifies this client in the bus.

This function returns an empty QString for peer-to-peer connections.

### QDBusMessage QDBusConnection::call ( const QDBusMessage & message, QDBus::CallMode mode = QDBus::Block, int timeout = -1 ) const

Sends the message over this connection and blocks, waiting for a reply, for at most timeout milliseconds. This function is suitable for method calls only. It returns the reply message as its return value, which will be either of type QDBusMessage::ReplyMessage or QDBusMessage::ErrorMessage.

See the QDBusInterface::call() function for a more friendly way of placing calls.

Warning: If mode is QDBus::BlockWithGui, this function will reenter the Qt event loop in order to wait for the reply. During the wait, it may deliver signals and other method calls to your application. Therefore, it must be prepared to handle a reentrancy whenever a call is placed with call().

### bool QDBusConnection::callWithCallback ( const QDBusMessage & message, QObject * receiver, const char * returnMethod, const char * errorMethod, int timeout = -1 ) const

Sends the message over this connection and returns immediately. When the reply is received, the method returnMethod is called in the receiver object. If an error occurs, the method errorMethod will be called instead.

If no reply is received within timeout milliseconds, an automatic error will be delivered indicating the expiration of the call. The default timeout is -1, which will be replaced with an implementation-defined value that is suitable for inter-process communications (generally, 25 seconds).

This function is suitable for method calls only. It is guaranteed that the slot will be called exactly once with the reply, as long as the parameter types match and no error occurs.

Returns true if the message was sent, or false if the message could not be sent.

### bool QDBusConnection::callWithCallback ( const QDBusMessage & message, QObject * receiver, const char * returnMethod, int timeout = -1 ) const

This function is deprecated.

This is an overloaded member function, provided for convenience.

Sends the message over this connection and returns immediately. When the reply is received, the method returnMethod is called in the receiver object.

This function is suitable for method calls only. It is guaranteed that the slot will be called exactly once with the reply, as long as the parameter types match and no error occurs.

This function is dangerous because it cannot report errors, including the expiration of the timeout.

Returns true if the message was sent, or false if the message could not be sent.

### bool QDBusConnection::connect ( const QString & service, const QString & path, const QString & interface, const QString & name, QObject * receiver, const char * slot )

Connects the signal specified by the service, path, interface and name parameters to the slot slot in object receiver. The arguments service and path can be empty, denoting a connection to any signal of the (interface, name) pair, from any remote application.

Returns true if the connection was successful.

Warning: The signal will only be delivered to the slot if the parameters match. This verification can be done only when the signal is received, not at connection time.

### bool QDBusConnection::connect ( const QString & service, const QString & path, const QString & interface, const QString & name, const QString & signature, QObject * receiver, const char * slot )

This is an overloaded member function, provided for convenience.

Connects the signal to the slot slot in object receiver. Unlike the other connect() overload, this function allows one to specify the parameter signature to be connected using the signature variable. The function will then verify that this signature can be delivered to the slot specified by slot and return false otherwise.

Note: This function verifies that the signal signature matches the slot's parameters, but it does not verify that the actual signal exists with the given signature in the remote service.

### QDBusConnection QDBusConnection::connectToBus ( BusType type, const QString & name ) `[static]`

Opens a connection of type type to one of the known busses and associate with it the connection name name. Returns a QDBusConnection object associated with that connection.

### QDBusConnection QDBusConnection::connectToBus ( const QString & address, const QString & name ) `[static]`

This is an overloaded member function, provided for convenience.

Opens a peer-to-peer connection on address address and associate with it the connection name name. Returns a QDBusConnection object associated with that connection.

### bool QDBusConnection::disconnect ( const QString & service, const QString & path, const QString & interface, const QString & name, QObject * receiver, const char * slot )

Disconnects the signal specified by the service, path, interface and name parameters from the slot slot in object receiver. The arguments service and path can be empty, denoting a disconnection from all signals of the (interface, name) pair, from all remote applications.

Returns true if the disconnection was successful.

### bool QDBusConnection::disconnect ( const QString & service, const QString & path, const QString & interface, const QString & name, const QString & signature, QObject * receiver, const char * slot )

This is an overloaded member function, provided for convenience.

Disconnects the signal from the slot slot in object receiver. Unlike the other disconnect() overload, this function allows one to specify the parameter signature to be disconnected using the signature variable. The function will then verify that this signature is connected to the slot specified by slot and return false otherwise.

### void QDBusConnection::disconnectFromBus ( const QString & name ) `[static]`

Closes the connection of name name.

Note that if there are still QDBusConnection objects associated with the same connection, the connection will not be closed until all references are dropped. However, no further references can be created using the QDBusConnection constructor.

### QDBusConnectionInterface * QDBusConnection::interface () const

Returns a QDBusConnectionInterface object that represents the D-BUS server interface on this connection.

### bool QDBusConnection::isConnected () const

Returns true if this QDBusConnection object is connected.

If it isn't connected, calling connectToBus() on the same connection name will not make be connected. You need to call the QDBusConnection constructor again.

### QDBusError QDBusConnection::lastError () const

Returns the last error that happened in this connection.

This function is provided for low-level code. If you're using QDBusInterface::call(), error codes are reported by its return value.

See also QDBusInterface and QDBusMessage.

### QObject * QDBusConnection::objectRegisteredAt ( const QString & path ) const

Return the object that was registered with the registerObject() at the object path given by path.

### bool QDBusConnection::registerObject ( const QString & path, QObject * object, RegisterOptions options = ExportAdaptors )

Registers the object object at path path and returns true if the registration was successful. The options parameter specifies how much of the object object will be exposed through D-Bus.

This function does not replace existing objects: if there is already an object registered at path path, this function will return false. Use unregisterObject() to unregister it first.

You cannot register an object as a child object of an object that was registered with QDBusConnection::ExportChildObjects.

### bool QDBusConnection::registerService ( const QString & serviceName )

Attempts to register the serviceName on the D-BUS server and returns true if the registration succeded. The registration will fail if the name is already registered by another application.

See also unregisterService() and QDBusConnectionInterface::registerService().

### bool QDBusConnection::send ( const QDBusMessage & message ) const

Sends the message over this connection, without waiting for a reply. This is suitable for errors, signals, and return values as well as calls whose return values are not necessary.

Returns true if the message was queued successfully, false otherwise.

### QDBusConnection QDBusConnection::sender () `[static]`

Returns the connection that sent the signal, if called in a slot activated by QDBus; otherwise it returns 0.

### QDBusConnection QDBusConnection::sessionBus () `[static]`

Returns a QDBusConnection object opened with the session bus. The object reference returned by this function is valid until the QCoreApplication's destructor is run, when the connection will be closed and the object, deleted.

### QDBusConnection QDBusConnection::systemBus () `[static]`

Returns a QDBusConnection object opened with the system bus. The object reference returned by this function is valid until the QCoreApplication's destructor is run, when the connection will be closed and the object, deleted.

### void QDBusConnection::unregisterObject ( const QString & path, UnregisterMode mode = UnregisterNode )

Unregisters an object that was registered with the registerObject() at the object path given by path and, if mode is QDBusConnection::UnregisterTree, all of its sub-objects too.

Note that you cannot unregister objects that were not registered with registerObject().

### bool QDBusConnection::unregisterService ( const QString & serviceName )

Unregisters the service serviceName that was previously registered with registerService() and returns true if it succeeded.

See also registerService() and QDBusConnectionInterface::unregisterService().

### QDBusConnection & QDBusConnection::operator= ( const QDBusConnection & other )

Creates a copy of the connection other in this object. Note that the connection this object referenced before the copy, is not spontaneously disconnected.

See also disconnectFromBus().

## Related Non-Members

### QDBusConnection QDBusConnection::sessionBus () `[static]`

Returns a QDBusConnection object opened with the session bus. The object reference returned by this function is valid until the QCoreApplication's destructor is run, when the connection will be closed and the object, deleted.

### QDBusConnection QDBusConnection::systemBus () `[static]`

Returns a QDBusConnection object opened with the system bus. The object reference returned by this function is valid until the QCoreApplication's destructor is run, when the connection will be closed and the object, deleted.