class QSocketNotifier#

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

Synopsis#

Methods#

def __init__()
def isEnabled()
def isValid()
def setSocket()
def socket()
def type()

Slots#

def setEnabled()

Signals#

def activated()

Note

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Detailed Description#

The QSocketNotifier makes it possible to integrate Qt’s event loop with other event loops based on file descriptors. File descriptor action is detected in Qt’s main event loop ( 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. If the descriptor is passed to the notifier’s constructor, 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.

You can create a socket notifier with no descriptor assigned. In this case, you should call the setSocket() function after the descriptor has been obtained.

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.

See also

QFile QProcess QTcpSocketQUdpSocket

class 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.

Constant

Description

QSocketNotifier.Read

There is data to be read.

QSocketNotifier.Write

Data can be written.

QSocketNotifier.Exception

An exception has occurred. We recommend against using this.

See also

QSocketNotifier() type()

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

__init__(arg__1, arg__2[, parent=None])#

Parameters:

arg__1 – object
arg__2 – Type
parent – QObject

__init__(arg__1[, parent=None])

Parameters:

arg__1 – Type
parent – QObject

Constructs a socket notifier with the given type that has no descriptor assigned. The parent argument is passed to QObject ‘s constructor.

Call the setSocket() function to set the descriptor for monitoring.

See also

setSocket() isValid() isEnabled()

__init__(socket, arg__2[, parent=None])

Parameters:

socket – qintptr
arg__2 – Type
parent – QObject

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()

activated(socket, activationEvent)#

Parameters:

socket – QSocketDescriptor
activationEvent – Type

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() socket()

isEnabled()#

Return type:: bool

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

See also

setEnabled()

isValid()#

Return type:: bool

Returns true if the notifier is valid (that is, it has a descriptor assigned); otherwise returns false.

See also

setSocket()

setEnabled(arg__1)#

Parameters:: arg__1 – bool

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

When the notifier is enabled, it emits the activated() signal whenever a socket event corresponding to its type occurs. When 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()

setSocket(socket)#

Parameters:: socket – qintptr

Assigns the socket to this notifier.

Note

The notifier will be disabled as a side effect and needs to be re-enabled.