Viadeo Twitter Google Bookmarks ! Facebook Digg del.icio.us MySpace Yahoo MyWeb Blinklist Netvouz Reddit Simpy StumbleUpon Bookmarks Windows Live Favorites 
Logo Documentation Qt ·  Page d'accueil  ·  Toutes les classes  ·  Toutes les fonctions  ·  Vues d'ensemble  · 

QSocketNotifier Class Reference

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

 #include <QSocketNotifier>

Inherits: QObject.

Public Types

enum Type { Read, Write, Exception }

Public Functions

QSocketNotifier ( int socket, Type type, QObject * parent = 0 )
~QSocketNotifier ()
bool isEnabled () const
int socket () const
Type type () const
  • 29 public functions inherited from QObject

Public Slots

void setEnabled ( bool enable )
  • 1 public slot inherited from QObject

Signals

void activated ( int socket )

Reimplemented Protected Functions

virtual bool event ( QEvent * e )
  • 7 protected functions inherited from QObject

Additional Inherited Members

  • 1 property inherited from QObject
  • 5 static public members inherited from QObject
  • 7 protected functions inherited from QObject

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:

  1. Disable the notifier.
  2. Read data from the socket.
  3. 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:

  1. Disable the notifier.
  2. Write as much data as you can (before EWOULDBLOCK is returned).
  3. 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, and QUdpSocket.

Member Type Documentation

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.

ConstantValueDescription
QSocketNotifier::Read0There is data to be read.
QSocketNotifier::Write1Data can be written.
QSocketNotifier::Exception2An exception has occurred. We recommend against using this.

See also QSocketNotifier() and type().

Member Function Documentation

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() and isEnabled().

QSocketNotifier::~QSocketNotifier ()

Destroys this socket notifier.

void QSocketNotifier::activated ( int socket ) [signal]

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

The socket identifier is passed in the socket parameter.

See also type() and socket().

bool QSocketNotifier::event ( QEvent * e ) [virtual protected]

Reimplemented from QObject::event().

bool QSocketNotifier::isEnabled () const

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

See also 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() and activated().

int QSocketNotifier::socket () const

Returns the socket identifier specified to the constructor.

See also type().

Type QSocketNotifier::type () const

Returns the socket event type specified to the constructor.

See also socket().

Publicité

Best Of

Actualités les plus lues

Semaine
Mois
Année
  1. « Quelque chose ne va vraiment pas avec les développeurs "modernes" », un développeur à "l'ancienne" critique la multiplication des bibliothèques 44
  2. Microsoft ouvre aux autres compilateurs C++ AMP, la spécification pour la conception d'applications parallèles C++ utilisant le GPU 22
  3. Les développeurs ignorent-ils trop les failles découvertes dans leur code ? Prenez-vous en compte les remarques des autres ? 17
  4. RIM : « 13 % des développeurs ont gagné plus de 100 000 $ sur l'AppWord », Qt et open-source au menu du BlackBerry DevCon Europe 0
  5. BlackBerry 10 : premières images du prochain OS de RIM qui devrait intégrer des widgets et des tuiles inspirées de Windows Phone 0
  6. Quelles nouveautés de C++11 Visual C++ doit-il rapidement intégrer ? Donnez-nous votre avis 10
  7. Adieu qmake, bienvenue qbs : Qt Building Suite, un outil déclaratif et extensible pour la compilation de projets Qt 17
Page suivante

Le blog Digia au hasard

Logo

Déploiement d'applications Qt Commercial sur les tablettes Windows 8

Le blog Digia est l'endroit privilégié pour la communication sur l'édition commerciale de Qt, où des réponses publiques sont apportées aux questions les plus posées au support. Lire l'article.

Communauté

Ressources

Liens utiles

Contact

  • Vous souhaitez rejoindre la rédaction ou proposer un tutoriel, une traduction, une question... ? Postez dans le forum Contribuez ou contactez-nous par MP ou par email (voir en bas de page).

Qt dans le magazine

Cette page est une traduction d'une page de la documentation de Qt, écrite par Nokia Corporation and/or its subsidiary(-ies). Les éventuels problèmes résultant d'une mauvaise traduction ne sont pas imputables à Nokia. Qt 4.7
Copyright © 2012 Developpez LLC. Tous droits réservés Developpez LLC. Aucune reproduction, même partielle, ne peut être faite de ce site et de l'ensemble de son contenu : textes, documents et images sans l'autorisation expresse de Developpez LLC. Sinon, vous encourez selon la loi jusqu'à 3 ans de prison et jusqu'à 300 000 E de dommages et intérêts. Cette page est déposée à la SACD.
Vous avez déniché une erreur ? Un bug ? Une redirection cassée ? Ou tout autre problème, quel qu'il soit ? Ou bien vous désirez participer à ce projet de traduction ? N'hésitez pas à nous contacter ou par MP !
 
 
 
 
Partenaires

Hébergement Web