The QSocketNotifier class provides support for monitoring activity on a file descriptor. More...

#include <qsocketnotifier.h>

Inheritance diagram for QSocketNotifier:

Public Types
enum	Type { Read, Write, Exception }
	This enum describes the various types of events that a socket notifier can recognize. More...

Public Slots
void	setEnabled (bool)
	If enable is true, the notifier is enabled; otherwise the notifier is disabled. More...

Public Slots inherited from QObject
void	deleteLater ()
	Schedules this object for deletion. More...

Signals
void	activated (int socket)
	This signal is emitted whenever the socket notifier is enabled and a socket event corresponding to its Type{type} occurs. More...

Signals inherited from QObject
void	destroyed (QObject *=0)
	This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More...

Public Functions
bool	isEnabled () const
	Returns true if the notifier is enabled; otherwise returns false. More...

	QSocketNotifier (int socket, Type, QObject *parent=0)
	Constructs a socket notifier with the given parent. More...

int	socket () const
	Returns the socket identifier specified to the constructor. More...

Type	type () const
	Returns the socket event type specified to the constructor. More...

	~QSocketNotifier ()
	Destroys this socket notifier. More...

Public Functions inherited from QObject
bool	blockSignals (bool b)
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More...

const QObjectList &	children () const
	Returns a list of child objects. More...

bool	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const

bool	disconnect (const char signal=0, const QObject receiver=0, const char *member=0)

bool	disconnect (const QObject receiver, const char member=0)

void	dumpObjectInfo ()
	Dumps information about signal connections, etc. More...

void	dumpObjectTree ()
	Dumps a tree of children to the debug output. More...

QList< QByteArray >	dynamicPropertyNames () const
	Returns the names of all properties that were dynamically added to the object using setProperty(). More...

virtual bool	eventFilter (QObject , QEvent )
	Filters events if this object has been installed as an event filter for the watched object. More...

template<typename T >
T	findChild (const QString &aName=QString()) const
	Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More...

template<typename T >
QList< T >	findChildren (const QString &aName=QString()) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. More...

template<typename T >
QList< T >	findChildren (const QRegExp &re) const

bool	inherits (const char *classname) const
	Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false. More...

void	installEventFilter (QObject *)
	Installs an event filter filterObj on this object. More...

bool	isWidgetType () const
	Returns true if the object is a widget; otherwise returns false. More...

void	killTimer (int id)
	Kills the timer with timer identifier, id. More...

virtual const QMetaObject *	metaObject () const
	Returns a pointer to the meta-object of this object. More...

void	moveToThread (QThread *thread)
	Changes the thread affinity for this object and its children. More...

QString	objectName () const

QObject *	parent () const
	Returns a pointer to the parent object. More...

QVariant	property (const char *name) const
	Returns the value of the object's name property. More...

Q_INVOKABLE	QObject (QObject *parent=0)
	Constructs an object with parent object parent. More...

void	removeEventFilter (QObject *)
	Removes an event filter object obj from this object. More...

void	setObjectName (const QString &name)

void	setParent (QObject *)
	Makes the object a child of parent. More...

bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value. More...

void	setUserData (uint id, QObjectUserData *data)

bool	signalsBlocked () const
	Returns true if signals are blocked; otherwise returns false. More...

int	startTimer (int interval)
	Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More...

QThread *	thread () const
	Returns the thread in which the object lives. More...

QObjectUserData *	userData (uint id) const

virtual	~QObject ()
	Destroys the object, deleting all its child objects. More...

Protected Functions
bool	event (QEvent *)
	This virtual function receives events to an object and should return true if the event e was recognized and processed. More...

Protected Functions inherited from QObject
virtual void	childEvent (QChildEvent *)
	This event handler can be reimplemented in a subclass to receive child events. More...

virtual void	connectNotify (const char *signal)
	This virtual function is called when something has been connected to signal in this object. More...

virtual void	customEvent (QEvent *)
	This event handler can be reimplemented in a subclass to receive custom events. More...

virtual void	disconnectNotify (const char *signal)
	This virtual function is called when something has been disconnected from signal in this object. More...

	QObject (QObjectPrivate &dd, QObject *parent=0)

int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal. More...

QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0. More...

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *)
	This event handler can be reimplemented in a subclass to receive timer events for the object. More...

Properties
bool	snenabled

Type	sntype

int	sockfd

Additional Inherited Members
Static Public Functions inherited from QObject
static bool	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More...

static bool	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	Disconnects signal in object sender from method in object receiver. More...

static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)

static uint	registerUserData ()

static QString	tr (const char sourceText, const char comment=0, int n=-1)

static QString	trUtf8 (const char sourceText, const char comment=0, int n=-1)

Static Public Variables inherited from QObject
static const QMetaObject	staticMetaObject
	This variable stores the meta-object for the class. More...

Protected Variables inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Static Protected Variables inherited from QObject
static const QMetaObject	staticQtMetaObject

Related Functions inherited from QObject
T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()

QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QRegExp &regExp)()

T *	qobject_cast (QObject *object)

	QObjectList

void *	qt_find_obj_child (QObject parent, const char type, const QString &name)
	Returns a pointer to the object named name that inherits type and with a given parent. More...

Detailed Description

The QSocketNotifier class provides support for monitoring activity on a file descriptor.

The QSocketNotifier makes it possible to integrate Qt's event loop with other event loops based on file descriptors. For example, the CORBA Framework uses it to process CORBA events. File descriptor action is detected in Qt's main event loop (QCoreApplication::exec()).

Once you have opened a device using a low-level (usually platform-specific) API, you can create a socket notifier to monitor the file descriptor. The socket notifier is enabled by default, i.e. it emits the activated() signal whenever a socket event corresponding to its type occurs. Connect the activated() signal to the slot you want to be called when an event corresponding to your socket notifier's type occurs.

There are three types of socket notifiers: read, write, and exception. The type is described by the Type enum, and must be specified when constructing the socket notifier. After construction it can be determined using the type() function. Note that if you need to monitor both reads and writes for the same file descriptor, you must create two socket notifiers. Note also that it is not possible to install two socket notifiers of the same type (Read , Write , Exception ) on the same socket.

The setEnabled() function allows you to disable as well as enable the socket notifier. It is generally advisable to explicitly enable or disable the socket notifier, especially for write notifiers. A disabled notifier ignores socket events (the same effect as not creating the socket notifier). Use the isEnabled() function to determine the notifier's current status.

Finally, you can use the socket() function to retrieve the socket identifier. Although the class is called QSocketNotifier, it is normally used for other types of devices than sockets. QTcpSocket and QUdpSocket provide notification through signals, so there is normally no need to use a QSocketNotifier on them.

Notes for Windows Users

The socket passed to QSocketNotifier will become non-blocking, even if it was created as a blocking socket. The activated() signal is sometimes triggered by high general activity on the host, even if there is nothing to read. A subsequent read from the socket can then fail, the error indicating that there is no data available (e.g., WSAEWOULDBLOCK). This is an operating system limitation, and not a bug in QSocketNotifier.

To ensure that the socket notifier handles read notifications correctly, follow these steps when you receive a notification:

Disable the notifier.
Read data from the socket.
Re-enable the notifier if you are interested in more data (such as after having written a new command to a remote server).

To ensure that the socket notifier handles write notifications correctly, follow these steps when you receive a notification:

Disable the notifier.
Write as much data as you can (before EWOULDBLOCK is returned).
Re-enable notifier if you have more data to write.

Further information: On Windows, Qt always disables the notifier after getting a notification, and only re-enables it if more data is expected. For example, if data is read from the socket and it can be used to read more, or if reading or writing is not possible because the socket would block, in which case it is necessary to wait before attempting to read or write again.

See also: QFile, QProcess, QTcpSocket, QUdpSocket

Definition at line 53 of file qsocketnotifier.h.

Enumerations

◆ Type

enum QSocketNotifier::Type

This enum describes the various types of events that a socket notifier can recognize.

The type must be specified when constructing the socket notifier.

Note that if you need to monitor both reads and writes for the same file descriptor, you must create two socket notifiers. Note also that it is not possible to install two socket notifiers of the same type (Read, Write, Exception) on the same socket.

Read There is data to be read.
Write Data can be written.
Exception An exception has occurred. We recommend against using this.

See also: QSocketNotifier(), type()

Enumerator
Read
Write
Exception

Definition at line 59 of file qsocketnotifier.h.

59 { Read, Write, Exception };

QSocketNotifier::Write

Definition: qsocketnotifier.h:59

QSocketNotifier::Read

Definition: qsocketnotifier.h:59

QSocketNotifier::Exception

Definition: qsocketnotifier.h:59

Constructors and Destructors

◆ QSocketNotifier()

QSocketNotifier::QSocketNotifier	(	int	socket,
		Type	type,
		QObject *	parent = `0`
	)

Constructs a socket notifier with the given parent.

It enables the socket, and watches for events of the given type.

It is generally advisable to explicitly enable or disable the socket notifier, especially for write notifiers.

Note for Windows users: The socket passed to QSocketNotifier will become non-blocking, even if it was created as a blocking socket.

See also: setEnabled(), isEnabled()

Definition at line 177 of file qsocketnotifier.cpp.

     : QObject(parent)
 {
     sockfd = socket;
     sntype = type;
     snenabled = true;
 
     Q_D(QObject);
     if (socket < 0)
         qWarning("QSocketNotifier: Invalid socket specified");
     else if (!d->threadData->eventDispatcher)
         qWarning("QSocketNotifier: Can only be used with threads started with QThread");
     else
         d->threadData->eventDispatcher->registerSocketNotifier(this);
 }

◆ ~QSocketNotifier()

QSocketNotifier::~QSocketNotifier ( )

Destroys this socket notifier.

Definition at line 231 of file qsocketnotifier.cpp.

 {
     setEnabled(false);
 }

Functions

◆ activated

void QSocketNotifier::activated ( int socket )

signal

This signal is emitted whenever the socket notifier is enabled and a socket event corresponding to its Type{type} occurs.

The socket identifier is passed in the socket parameter.

See also: type(), socket()

Referenced by event().

◆ event()

bool QSocketNotifier::event ( QEvent * e )

protectedvirtual

This virtual function receives events to an object and should return true if the event e was recognized and processed.

The event() function can be reimplemented to customize the behavior of an object.

See also: installEventFilter(), timerEvent(), QApplication::sendEvent(), QApplication::postEvent(), QWidget::event()

Reimplemented from QObject.

Reimplemented in QExceptionNotifier, QWriteNotifier, and QReadNotifier.

Definition at line 321 of file qsocketnotifier.cpp.

Referenced by QReadNotifier::event(), QWriteNotifier::event(), and QExceptionNotifier::event().

 {
     // Emits the activated() signal when a QEvent::SockAct is
     // received.
     if (e->type() == QEvent::ThreadChange) {
         if (snenabled) {
             QMetaObject::invokeMethod(this, "setEnabled", Qt::QueuedConnection,
                                       Q_ARG(bool, snenabled));
             setEnabled(false);
         }
     }
     QObject::event(e);                        // will activate filters
     if (e->type() == QEvent::SockAct) {
         emit activated(sockfd);
         return true;
     }
     return false;
 }

◆ isEnabled()

bool QSocketNotifier::isEnabled ( ) const

inline

Returns true if the notifier is enabled; otherwise returns false.

See also: setEnabled()

Definition at line 70 of file qsocketnotifier.h.

Referenced by QDirectFBMouseHandlerPrivate::setEnabled().

70 { return snenabled; }

QSocketNotifier::snenabled

bool snenabled

Definition: qsocketnotifier.h:86

◆ setEnabled

void QSocketNotifier::setEnabled ( bool enable )

slot

If enable is true, the notifier is enabled; otherwise the notifier is disabled.

The notifier is enabled by default, i.e. it emits the activated() signal whenever a socket event corresponding to its type occurs. If it is disabled, it ignores socket events (the same effect as not creating the socket notifier).

Write notifiers should normally be disabled immediately after the activated() signal has been emitted

See also: isEnabled(), activated()em>Reimplemented Function

Definition at line 301 of file qsocketnotifier.cpp.

Referenced by QUnixSocket::abort(), QUnixSocketServer::close(), QUnixSocket::connect(), QProcessPrivate::createChannel(), QEventDispatcherUNIXPrivate::doSelect(), QWSLinuxInputMousePrivate::enable(), event(), QUnixSocketServer::listen(), qDBusRealAddWatch(), QUnixSocket::read(), QUnixSocket::readData(), QVFbMouseHandler::resume(), QQnxMouseHandler::resume(), QDirectFBKeyboardHandlerPrivate::resume(), QWSTslibMouseHandlerPrivate::resume(), QWSLinuxTPMouseHandlerPrivate::resume(), QWSPcMouseHandlerPrivate::resume(), QDirectFBMouseHandlerPrivate::setEnabled(), QUnixSocket::setSocketDescriptor(), socketNotifierSourceCheck(), QVFbMouseHandler::suspend(), QQnxMouseHandler::suspend(), QDirectFBKeyboardHandlerPrivate::suspend(), QWSTslibMouseHandlerPrivate::suspend(), QWSLinuxTPMouseHandlerPrivate::suspend(), QWSPcMouseHandlerPrivate::suspend(), QUnixSocket::write(), and ~QSocketNotifier().

◆ socket()

int QSocketNotifier::socket ( ) const

inline

Returns the socket identifier specified to the constructor.

See also: type()

Definition at line 67 of file qsocketnotifier.h.

67 { return sockfd; }

QSocketNotifier::sockfd

int sockfd

Definition: qsocketnotifier.h:84

◆ type()

Type QSocketNotifier::type ( ) const

inline

Returns the socket event type specified to the constructor.

See also: socket()

Definition at line 68 of file qsocketnotifier.h.

68 { return sntype; }

QSocketNotifier::sntype

Type sntype

Definition: qsocketnotifier.h:85

Properties

◆ snenabled

bool QSocketNotifier::snenabled

private

Definition at line 86 of file qsocketnotifier.h.

Referenced by event(), QSocketNotifier(), and setEnabled().

◆ sntype

Type QSocketNotifier::sntype

private

Definition at line 85 of file qsocketnotifier.h.

Referenced by QSocketNotifier().

◆ sockfd

int QSocketNotifier::sockfd

private

Definition at line 84 of file qsocketnotifier.h.

Referenced by event(), QSocketNotifier(), and setEnabled().

The documentation for this class was generated from the following files:

/src/corelib/kernel/qsocketnotifier.h
/src/corelib/kernel/qsocketnotifier.cpp

Public Types

Public Slots

Signals

Public Functions

Protected Functions

Properties

Additional Inherited Members

Detailed Description

Notes for Windows Users

Enumerations

◆ Type

Constructors and Destructors

◆ QSocketNotifier()

◆ ~QSocketNotifier()

Functions

◆ activated

◆ event()

◆ isEnabled()

◆ setEnabled

◆ socket()

◆ type()

Properties

◆ snenabled

◆ sntype

◆ sockfd