class QDBusConnection

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

Synopsis

Methods

Static functions

Note

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Detailed Description

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.

Once disconnected, calling connectToBus() will not reestablish a connection, you must create a new QDBusConnection instance.

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 .

class BusType

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

Constant

Description

QDBusConnection.SessionBus

the session bus, associated with the running desktop session

QDBusConnection.SystemBus

the system bus, used to communicate with system-wide processes

QDBusConnection.ActivationBus

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.

class RegisterOption

(inherits enum.Flag) Specifies the options for registering objects with the connection. The possible values are:

Constant

Description

QDBusConnection.ExportAdaptors

export the contents of adaptors found in this object

QDBusConnection.ExportScriptableSlots

export this object’s scriptable slots

QDBusConnection.ExportScriptableSignals

export this object’s scriptable signals

QDBusConnection.ExportScriptableProperties

export this object’s scriptable properties

QDBusConnection.ExportScriptableInvokables

export this object’s scriptable invokables

QDBusConnection.ExportScriptableContents

shorthand form for ExportScriptableSlots | ExportScriptableSignals | ExportScriptableProperties

QDBusConnection.ExportNonScriptableSlots

export this object’s non-scriptable slots

QDBusConnection.ExportNonScriptableSignals

export this object’s non-scriptable signals

QDBusConnection.ExportNonScriptableProperties

export this object’s non-scriptable properties

QDBusConnection.ExportNonScriptableInvokables

export this object’s non-scriptable invokables

QDBusConnection.ExportNonScriptableContents

shorthand form for ExportNonScriptableSlots | ExportNonScriptableSignals | ExportNonScriptableProperties

QDBusConnection.ExportAllSlots

export all of this object’s slots

QDBusConnection.ExportAllSignals

export all of this object’s signals

QDBusConnection.ExportAllProperties

export all of this object’s properties

QDBusConnection.ExportAllInvokables

export all of this object’s invokables

QDBusConnection.ExportAllContents

export all of this object’s contents

QDBusConnection.ExportChildObjects

export this object’s child objects

See also

registerObject() QDBusAbstractAdaptor Using adaptors

class UnregisterMode

The mode for unregistering an object path:

Constant

Description

QDBusConnection.UnregisterNode

unregister this node only: do not unregister child objects

QDBusConnection.UnregisterTree

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.

class VirtualObjectRegisterOption
class ConnectionCapability

(inherits enum.Flag) This enum describes the available capabilities for a D-Bus connection.

Constant

Description

QDBusConnection.UnixFileDescriptorPassing

enables passing of Unix file descriptors to other processes (see QDBusUnixFileDescriptor )

See also

connectionCapabilities()

__init__(other)
Parameters:

other – QDBusConnection

Creates a copy of the other connection.

__init__(name)
Parameters:

name – str

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.

asyncCall(message[, timeout=-1])
Parameters:
Return type:

QDBusPendingCall

Sends the message over this connection and returns immediately. This function is suitable for method calls only. It returns an object of type QDBusPendingCall which can be used to track the status of the reply.

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 timeout is also the upper limit for waiting in QDBusPendingCall::waitForFinished().

See the asyncCall() function for a more friendly way of placing calls.

Note

Method calls to objects registered by the application itself are never asynchronous due to implementation limitations.

baseService()
Return type:

str

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.

call(message[, mode=QDBus.Block[, timeout=-1]])
Parameters:
Return type:

QDBusMessage

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 ReplyMessage or ErrorMessage .

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).

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

Warning

If mode is 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().

callWithCallback(message, receiver, slot[, timeout=-1])
Parameters:
Return type:

bool

This is an overloaded function.

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.

callWithCallback(message, receiver, returnMethod, errorMethod[, timeout=-1])
Parameters:

  • message – QDBusMessage

  • receiver – QObject

  • returnMethod – str

  • errorMethod – str

  • timeout – int

Return type:

bool

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.

connect(service, path, interface, name, receiver, slot)
Parameters:

  • service – str

  • path – str

  • interface – str

  • name – str

  • receiver – QObject

  • slot – str

Return type:

bool

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.

connect(service, path, interface, name, signature, receiver, slot)
Parameters:

  • service – str

  • path – str

  • interface – str

  • name – str

  • signature – str

  • receiver – QObject

  • slot – str

Return type:

bool

This is an overloaded function.

Connects the signal to the slot slot in object receiver. Unlike the previous 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.

Returns true if the connection was successful.

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.

connect(service, path, interface, name, argumentMatch, signature, receiver, slot)
Parameters:

  • service – str

  • path – str

  • interface – str

  • name – str

  • argumentMatch – list of strings

  • signature – str

  • receiver – QObject

  • slot – str

Return type:

bool

This is an overloaded function.

Connects the signal to the slot slot in object receiver. Unlike the previous 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.

The argumentMatch parameter lists the string parameters to be matched, in sequential order. Note that, to match an empty string, you need to pass a QString that is empty but not null (i.e., QString(“”)). A null QString skips matching at that position.

Returns true if the connection was successful.

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.

static connectToBus(type, name)
Parameters:
Return type:

QDBusConnection

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

static connectToBus(address, name)
Parameters:

  • address – str

  • name – str

Return type:

QDBusConnection

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

static connectToPeer(address, name)
Parameters:

  • address – str

  • name – str

Return type:

QDBusConnection

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.

connectionCapabilities()
Return type:

Combination of ConnectionCapability

Returns the capabilities of this connection as negotiated with the bus server or peer. If this QDBusConnection is not connected, this function returns no capabilities.

disconnect(service, path, interface, name, receiver, slot)
Parameters:

  • service – str

  • path – str

  • interface – str

  • name – str

  • receiver – QObject

  • slot – str

Return type:

bool

Disconnects the signal specified by the service, path, interface and name parameters from the slot slot in object receiver. The arguments must be the same as passed to the connect() function.

Returns true if the disconnection was successful.

disconnect(service, path, interface, name, signature, receiver, slot)
Parameters:

  • service – str

  • path – str

  • interface – str

  • name – str

  • signature – str

  • receiver – QObject

  • slot – str

Return type:

bool

This is an overloaded function.

Disconnects the signal specified by the service, path, interface, name, and signature parameters from the slot slot in object receiver. The arguments must be the same as passed to the connect() function.

Returns true if the disconnection was successful.

disconnect(service, path, interface, name, argumentMatch, signature, receiver, slot)
Parameters:

  • service – str

  • path – str

  • interface – str

  • name – str

  • argumentMatch – list of strings

  • signature – str

  • receiver – QObject

  • slot – str

Return type:

bool

This is an overloaded function.

Disconnects the signal specified by the service, path, interface, name, argumentMatch, and signature parameters from the slot slot in object receiver. The arguments must be the same as passed to the connect() function.

Returns true if the disconnection was successful.

static disconnectFromBus(name)
Parameters:

name – str

Closes the bus 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.

static disconnectFromPeer(name)
Parameters:

name – str

Closes the peer 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.

interface()
Return type:

QDBusConnectionInterface

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

internalPointer()
Return type:

void

isConnected()
Return type:

bool

Returns true if this QDBusConnection object is connected.

lastError()
Return type:

QDBusError

Returns the last error that happened in this connection.

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

static localMachineId()
Return type:

QByteArray

Returns the local machine ID as known to the D-Bus system. Each node or host that runs D-Bus has a unique identifier that can be used to distinguish it from other hosts if they are sharing resources like the filesystem.

Note that the local machine ID is not guaranteed to be persistent across boots of the system, so this identifier should not be stored in persistent storage (like the filesystem). It is guaranteed to remain constant only during the lifetime of this boot session.

name()
Return type:

str

Returns the connection name for this connection, as given as the name parameter to connectToBus() .

The connection name can be used to uniquely identify actual underlying connections to buses. Copies made from a single connection will always implicitly share the underlying connection, and hence will have the same connection name.

Inversely, two connections having different connection names will always either be connected to different buses, or have a different unique name (as returned by baseService() ) on that bus.

objectRegisteredAt(path)
Parameters:

path – str

Return type:

QObject

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

registerObject(path, object[, options=QDBusConnection.RegisterOption.ExportAdaptors])
Parameters:
Return type:

bool

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.

The ExportChildObjects flag exports child objects on D-Bus based on the path of the registered objects and the QObject::objectName of the child. Therefore, it is important for the child object to have an object name.

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

registerObject(path, interface, object[, options=QDBusConnection.RegisterOption.ExportAdaptors])
Parameters:
Return type:

bool

This is an overloaded function.

Registers the object object at path path with interface name interface 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.

The ExportChildObjects flag exports child objects on D-Bus based on the path of the registered objects and the QObject::objectName of the child. Therefore, it is important for the child object to have an object name.

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

registerService(serviceName)
Parameters:

serviceName – str

Return type:

bool

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

registerVirtualObject(path, object[, options=QDBusConnection.VirtualObjectRegisterOption.SingleNode])
Parameters:
Return type:

bool

send(message)
Parameters:

message – QDBusMessage

Return type:

bool

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.

static sessionBus()
Return type:

QDBusConnection

Returns a QDBusConnection object opened with the session bus. The object reference returned by this function is valid until the application terminates, at which point the connection will be closed and the object deleted.

swap(other)
Parameters:

other – QDBusConnection

Swaps this QDBusConnection instance with other.

static systemBus()
Return type:

QDBusConnection

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.

unregisterObject(path[, mode=QDBusConnection.UnregisterMode.UnregisterNode])
Parameters:

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

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

unregisterService(serviceName)
Parameters:

serviceName – str

Return type:

bool

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