Wt  4.0.5
Public Types | Public Member Functions | List of all members
Wt::WSocketNotifier Class Reference

A utility class for asynchronous notification of socket activity. More...

#include <Wt/WSocketNotifier.h>

Inheritance diagram for Wt::WSocketNotifier:
Inheritance graph

Public Types

enum  Type { Type::Read, Type::Write, Type::Exception }
 Enumeration that event type. More...
- Public Types inherited from Wt::WObject
typedef void(WObject::* Method) ()
 Typedef for a WObject method without arguments.

Public Member Functions

 WSocketNotifier (int socket, Type type)
 Creates a new socket notifier. More...
 ~WSocketNotifier ()
int socket () const
 Returns the socket.
Type type () const
 Returns the event type.
void setEnabled (bool enabled)
 Enables or disable the notifier. More...
bool isEnabled () const
 Returns if the notifier is enabled.
Signal< int > & activated ()
 Signal indicating an event. More...
- Public Member Functions inherited from Wt::WObject
void addChild (std::unique_ptr< WObject > child)
 Add a child WObject whose lifetime is determined by this WObject.
template<typename Child >
Child * addChild (std::unique_ptr< Child > child)
 Add a child WObject, returning a raw pointer. More...
std::unique_ptr< WObjectremoveChild (WObject *child)
 Remove a child WObject, so its lifetime is no longer determined by this WObject.
virtual const std::string id () const
 Returns the (unique) identifier for this object. More...
virtual void setObjectName (const std::string &name)
 Sets an object name. More...
virtual std::string objectName () const
 Returns the object name. More...
void resetLearnedSlots ()
 Resets learned stateless slot implementations. More...
template<class T >
void resetLearnedSlot (void(T::*method)())
 Resets a learned stateless slot implementation. More...
template<class T >
WStatelessSlot * implementStateless (void(T::*method)())
 Declares a slot to be stateless and learn client-side behaviour on first invocation. More...
template<class T >
WStatelessSlot * implementStateless (void(T::*method)(), void(T::*undoMethod)())
 Declares a slot to be stateless and learn client-side behaviour in advance. More...
void isNotStateless ()
 Marks the current function as not stateless. More...
template<class T >
WStatelessSlot * implementJavaScript (void(T::*method)(), const std::string &jsCode)
 Provides a JavaScript implementation for a method. More...
- Public Member Functions inherited from Wt::Core::observable
 observable () noexcept
 Default constructor.
virtual ~observable ()
 Destructor. More...
template<typename... Args, typename C >
auto bindSafe (void(C::*method)(Args...)) noexcept
 Protects a method call against object destruction. More...
template<typename... Args, typename C >
auto bindSafe (void(C::*method)(Args...) const) const noexcept
 Protects a const method call against object destruction. More...
template<typename Function >
auto bindSafe (const Function &function) noexcept
 Protects a function against object destruction. More...

Additional Inherited Members

- Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot * getStateless (Method method)
 On-demand stateless slot implementation. More...

Detailed Description

A utility class for asynchronous notification of socket activity.

Use a socket notifier to integrate listening for socket events into the Wt event loop. In this way, you do not need a separate thread to listen for socket activity. Socket activity is either the availability of data to be read (Read event), possibility to write data (Write event), or an exception that occurred (Exception event).

When an event on a socket is available, the notifier emits the activated() signal. As in the case of a user interface event (like for example WInteractWidget::clicked()), you will typically modify the widget tree in response to the event. But, unless you use a timer (WTimer) or use server-initiated updates (see WApplication::triggerUpdates()), these changes are not propagated to the user interface, until the next user interface event.

Like other events, socket notification events are serial (not simultaneous), and there are no thread safety issues (you don't need to take the WApplication::UpdateLock).

std::unique_ptr<Wt::WSocketNotifier> notifier_;
void init() {
int sock = ...
notifier_ = std::make_unique<Wt::WSocketNotifier>(sock, Wt::WSocketNotifier::Read);
notifier_->activated().connect(this, &HelloApplication::readData);
void readData() {
// data is available on socket, or socket was closed by peer
char buf[100];
int s = read(notifier_->socket(), buf, 99);
if (s > 0) {
} else {
// closed by peer

Member Enumeration Documentation

◆ Type

Enumeration that event type.


Ready to read.


Ready to write.



Constructor & Destructor Documentation

◆ WSocketNotifier()

Wt::WSocketNotifier::WSocketNotifier ( int  socket,
Type  type 

Creates a new socket notifier.

Create a new socket listener to listen for events of given type on a socket with file descriptor socket. The WSocketNotifier is enabled after construction.

Member Function Documentation

◆ activated()

Signal<int>& Wt::WSocketNotifier::activated ( )

Signal indicating an event.

The signal is emitted when an event that was waited for is available. The signal argument is socket().

◆ setEnabled()

void Wt::WSocketNotifier::setEnabled ( bool  enabled)

Enables or disable the notifier.

By default, the socket notifier is enabled to receive events. When disabled, no events will be notified (as if the socket notifier didn't exist).

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