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# QDBusConnection Class Reference
[QtDBus module]

A connection to the D-Bus bus daemon. More...

    #include <QDBusConnection>

- List of all members, including inherited members

### Public Types

- enum BusType { SessionBus, SystemBus, ActivationBus }
- enum RegisterOption { ExportAdaptors, ExportSlots, ExportSignals, ExportProperties, ..., 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 call ( const QDBusMessage & message, QObject * receiver, const char * method, int timeout = -1 ) const
- 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 )
- QDBusConnectionInterface * interface () const
- bool isConnected () const
- QDBusError lastError () 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 addConnection ( BusType type, const QString & name )
- QDBusConnection addConnection ( const QString & address, const QString & name )
- void closeConnection ( const QString & name )

### Related Non-Members

- QDBusConnection sessionBus ()
- QDBusConnection systemBus ()

## Detailed Description

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 QDBusConnection::addConnection() 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 QDBusConnection::closeConnection() function.

As a convenience for the two most common connection types, the QDBus::sessionBus() and QDBus::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 QDBusConnection::addConnection() 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, whose purpose I have no idea...

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::ExportSlots` | `0x10` | export this object's scriptable slots
`QDBusConnection::ExportSignals` | `0x20` | export this object's scriptable signals
`QDBusConnection::ExportProperties` | `0x40` | export this object's scriptable properties
`QDBusConnection::ExportContents` | `0xf0` | shorthand form for ExportSlots | ExportSignals | ExportProperties
`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::ExportChildObjects` | `0x1000` | export this object's child objects

Warning: It is currently not possible to export signals from objects. If you pass the flag ExportSignals or ExportNonScriptableSignals, the registerObject() function will print a warning.

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 QDBusConnection::addConnection 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 QDBusConnection::closeConnection to do that.

### QDBusConnection QDBusConnection::addConnection ( 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::addConnection ( 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.

### 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. 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 `UseEventLoop`, 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 sendWithReply.

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

This is an overloaded member function, provided for convenience.

Sends the message over this connection and returns immediately after queueing it. When the reply is received, the slot method is called in the object receiver. This function is suitable for method calls only.

This function guarantees that the slot will be called exactly once with the reply, as long as the parameter types match. If they don't, the reply cannot be delivered.

Returns the identification of the message that was sent or 0 if nothing was sent.

### void QDBusConnection::closeConnection ( 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::QDBusConnection constructor.

### 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 QDBusConnection::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.

### 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 QDBusConnection::addConnection 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.

### 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.

### 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. The connection this object referenced before the copy is not spontaneously disconnected. See QDBusConnection::closeConnection for more information.

## Related Non-Members

### QDBusConnection QDBus::sessionBus ()

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 QDBus::systemBus ()

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.