The QTcpServer class provides a TCP-based server. More...

#include <qtcpserver.h>

Inheritance diagram for QTcpServer:

Collaboration diagram for QTcpServer:

Signals
void	newConnection ()
	This signal is emitted every time a new connection is available, regardless of whether it has been added to the pending connections queue or not.

void	pendingConnectionAvailable (QPrivateSignal)
	This signal is emitted every time a new connection has been added to the pending connections queue.

void	acceptError (QAbstractSocket::SocketError socketError)

Signals inherited from QObject
void	destroyed (QObject *=nullptr)
	This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.

void	objectNameChanged (const QString &objectName, QPrivateSignal)
	This signal is emitted after the object's name has been changed.

Public Member Functions
	QTcpServer (QObject *parent=nullptr)
	Constructs a QTcpServer object.

virtual	~QTcpServer ()
	Destroys the QTcpServer object.

bool	listen (const QHostAddress &address=QHostAddress::Any, quint16 port=0)
	Tells the server to listen for incoming connections on address address and port port.

void	close ()
	Closes the server.

bool	isListening () const
	Returns `true` if the server is currently listening for incoming connections; otherwise returns `false`.

void	setMaxPendingConnections (int numConnections)
	Sets the maximum number of pending accepted connections to numConnections.

int	maxPendingConnections () const
	Returns the maximum number of pending accepted connections.

void	setListenBacklogSize (int size)
	Sets the backlog queue size of to be accepted connections to size.

int	listenBacklogSize () const
	Returns the backlog queue size of to be accepted connections.

quint16	serverPort () const
	Returns the server's port if the server is listening for connections; otherwise returns 0.

QHostAddress	serverAddress () const
	Returns the server's address if the server is listening for connections; otherwise returns QHostAddress::Null.

qintptr	socketDescriptor () const
	Returns the native socket descriptor the server uses to listen for incoming instructions, or -1 if the server is not listening.

bool	setSocketDescriptor (qintptr socketDescriptor)
	Sets the socket descriptor this server should use when listening for incoming connections to socketDescriptor.

bool	waitForNewConnection (int msec=0, bool *timedOut=nullptr)
	Waits for at most msec milliseconds or until an incoming connection is available.

virtual bool	hasPendingConnections () const
	Returns `true` if the server has a pending connection; otherwise returns `false`.

virtual QTcpSocket *	nextPendingConnection ()
	Returns the next pending connection as a connected QTcpSocket object.

QAbstractSocket::SocketError	serverError () const
	Returns an error code for the last error that occurred.

QString	errorString () const
	Returns a human readable description of the last error that occurred.

void	pauseAccepting ()

void	resumeAccepting ()

void	setProxy (const QNetworkProxy &networkProxy)

QNetworkProxy	proxy () const

Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)
	Constructs an object with parent object parent.

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

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

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

QString	objectName () const

Q_WEAK_OVERLOAD void	setObjectName (const QString &name)
	Sets the object's name to name.

void	setObjectName (QAnyStringView name)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QBindable< QString >	bindableObjectName ()

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

bool	isWindowType () const
	Returns `true` if the object is a window; otherwise returns `false`.

bool	isQuickItemType () const
	Returns `true` if the object is a QQuickItem; otherwise returns `false`.

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

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

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

bool	moveToThread (QThread *thread QT6_DECL_NEW_OVERLOAD_TAIL)
	Changes the thread affinity for this object and its children and returns `true` on success.

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
	This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.

int	startTimer (std::chrono::nanoseconds time, Qt::TimerType timerType=Qt::CoarseTimer)

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

void	killTimer (Qt::TimerId id)

template<typename T >
T	findChild (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.

template<typename T >
QList< T >	findChildren (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) 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.

template<typename T >
T	findChild (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

template<typename T >
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

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

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

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

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

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

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

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

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

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

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

bool	setProperty (const char *name, QVariant &&value)

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

QList< QByteArray >	dynamicPropertyNames () const

QBindingStorage *	bindingStorage ()

const QBindingStorage *	bindingStorage () const

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

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`.

Protected Member Functions
virtual void	incomingConnection (qintptr handle)
	This virtual function is called by QTcpServer when a new connection is available.

void	addPendingConnection (QTcpSocket *socket)
	This function is called by QTcpServer::incomingConnection() to add the socket to the list of pending incoming connections.

	QTcpServer (QAbstractSocket::SocketType socketType, QTcpServerPrivate &dd, QObject *parent=nullptr)

Protected Member Functions inherited from QObject
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 \nullptr.

int	senderSignalIndex () const

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

bool	isSignalConnected (const QMetaMethod &signal) const

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

virtual void	childEvent (QChildEvent *event)
	This event handler can be reimplemented in a subclass to receive child events.

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

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	disconnectNotify (const QMetaMethod &signal)

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

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

Static Public Member Functions inherited from QObject
static QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	\threadsafe

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

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	\threadsafe

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

static bool	disconnect (const QMetaObject::Connection &)
	Disconnect a connection.

template<typename Func1 , typename Func2 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object receiver, Func2 slot)

template<typename Func1 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject receiver, void **zero)

Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Properties inherited from QObject
QString	objectName
	the name of this object

Related Symbols inherited from QObject
template< class T > T	qobject_cast (const QObject *object)
	Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.

template< typename T > T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

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

	QObjectList
	\macro Q_CLASSINFO(Name, Value)

Detailed Description

The QTcpServer class provides a TCP-based server.

\reentrant

\inmodule QtNetwork

This class makes it possible to accept incoming TCP connections. You can specify the port or have QTcpServer pick one automatically. You can listen on a specific address or on all the machine's addresses.

Call listen() to have the server listen for incoming connections. The newConnection() signal is then emitted each time a client connects to the server. When the client connection has been added to the pending connection queue using the addPendingConnection() function, the pendingConnectionAvailable() signal is emitted.

Call nextPendingConnection() to accept the pending connection as a connected QTcpSocket. The function returns a pointer to a QTcpSocket in QAbstractSocket::ConnectedState that you can use for communicating with the client.

If an error occurs, serverError() returns the type of error, and errorString() can be called to get a human readable description of what happened.

When listening for connections, the address and port on which the server is listening are available as serverAddress() and serverPort().

Calling close() makes QTcpServer stop listening for incoming connections.

Although QTcpServer is mostly designed for use with an event loop, it's possible to use it without one. In that case, you must use waitForNewConnection(), which blocks until either a connection is available or a timeout expires.

See also: QTcpSocket, {Fortune Server}, {Threaded Fortune Server}, {Torrent Example}

Definition at line 21 of file qtcpserver.h.

Constructor & Destructor Documentation

◆ QTcpServer() [1/2]

QTcpServer::QTcpServer ( QObject * parent = nullptr )

explicit

Constructs a QTcpServer object.

parent is passed to the QObject constructor.

See also: listen(), setSocketDescriptor()

Definition at line 229 of file qtcpserver.cpp.

◆ ~QTcpServer()

QTcpServer::~QTcpServer ( )

virtual

Destroys the QTcpServer object.

If the server is listening for connections, the socket is automatically closed.

Any client \l{QTcpSocket}s that are still connected must either disconnect or be reparented before the server is deleted.

See also: close()

Definition at line 248 of file qtcpserver.cpp.

◆ QTcpServer() [2/2]

QTcpServer::QTcpServer	(	QAbstractSocket::SocketType	socketType,
		QTcpServerPrivate &	dd,
		QObject *	parent = nullptr )

protected

Constructs a new server object with socket of type socketType. The parent argument is passed to QObject's constructor.

Definition at line 261 of file qtcpserver.cpp.

Member Function Documentation

◆ acceptError

void QTcpServer::acceptError ( QAbstractSocket::SocketError socketError )

signal

Since: 5.0

This signal is emitted when accepting a new connection results in an error. The socketError parameter describes the type of error that occurred.

See also: pauseAccepting(), resumeAccepting()

◆ addPendingConnection()

void QTcpServer::addPendingConnection ( QTcpSocket * socket )

protected

This function is called by QTcpServer::incomingConnection() to add the socket to the list of pending incoming connections.

Note: Don't forget to call this member from reimplemented incomingConnection() if you do not want to break the Pending Connections mechanism. This function emits the pendingConnectionAvailable() signal after the socket has been added.

See also: incomingConnection(), pendingConnectionAvailable()

Since: 4.7

Definition at line 610 of file qtcpserver.cpp.

◆ close()

void QTcpServer::close ( )

Closes the server.

The server will no longer listen for incoming connections.

See also: listen()

Definition at line 365 of file qtcpserver.cpp.

◆ errorString()

QString QTcpServer::errorString ( ) const

Returns a human readable description of the last error that occurred.

See also: serverError()

Definition at line 691 of file qtcpserver.cpp.

◆ hasPendingConnections()

bool QTcpServer::hasPendingConnections ( ) const

virtual

Returns true if the server has a pending connection; otherwise returns false.

See also: nextPendingConnection(), setMaxPendingConnections()

Definition at line 521 of file qtcpserver.cpp.

◆ incomingConnection()

void QTcpServer::incomingConnection ( qintptr socketDescriptor )

protectedvirtual

This virtual function is called by QTcpServer when a new connection is available.

The socketDescriptor argument is the native socket descriptor for the accepted connection.

The base implementation creates a QTcpSocket, sets the socket descriptor and then stores the QTcpSocket in an internal list of pending connections. Finally newConnection() is emitted.

Reimplement this function to alter the server's behavior when a connection is available.

If this server is using QNetworkProxy then the socketDescriptor may not be usable with native socket functions, and should only be used with QTcpSocket::setSocketDescriptor().

Note: If another socket is created in the reimplementation of this method, it needs to be added to the Pending Connections mechanism by calling addPendingConnection().; If you want to handle an incoming connection as a new QTcpSocket object in another thread you have to pass the socketDescriptor to the other thread and create the QTcpSocket object there and use its setSocketDescriptor() method.

See also: newConnection(), nextPendingConnection(), addPendingConnection()

Reimplemented in QSctpServer, and QSslServer.

Definition at line 586 of file qtcpserver.cpp.

◆ isListening()

bool QTcpServer::isListening ( ) const

Returns true if the server is currently listening for incoming connections; otherwise returns false.

See also: listen()

Definition at line 352 of file qtcpserver.cpp.

◆ listen()

bool QTcpServer::listen	(	const QHostAddress &	address = QHostAddress::Any,
		quint16	port = 0 )

Tells the server to listen for incoming connections on address address and port port.

If port is 0, a port is chosen automatically. If address is QHostAddress::Any, the server will listen on all network interfaces.

Returns true on success; otherwise returns false.

See also: isListening()

Definition at line 285 of file qtcpserver.cpp.

◆ listenBacklogSize()

int QTcpServer::listenBacklogSize ( ) const

Returns the backlog queue size of to be accepted connections.

Since: 6.3

See also: setListenBacklogSize()

Definition at line 670 of file qtcpserver.cpp.

◆ maxPendingConnections()

int QTcpServer::maxPendingConnections ( ) const

Returns the maximum number of pending accepted connections.

The default is 30.

See also: setMaxPendingConnections(), hasPendingConnections()

Definition at line 642 of file qtcpserver.cpp.

◆ newConnection

void QTcpServer::newConnection ( )

signal

This signal is emitted every time a new connection is available, regardless of whether it has been added to the pending connections queue or not.

See also: hasPendingConnections(), nextPendingConnection()

◆ nextPendingConnection()

QTcpSocket * QTcpServer::nextPendingConnection ( )

virtual

Returns the next pending connection as a connected QTcpSocket object.

The socket is created as a child of the server, which means that it is automatically deleted when the QTcpServer object is destroyed. It is still a good idea to delete the object explicitly when you are done with it, to avoid wasting memory.

\nullptr is returned if this function is called when there are no pending connections.

Note: The returned QTcpSocket object cannot be used from another thread. If you want to use an incoming connection from another thread, you need to override incomingConnection().

See also: hasPendingConnections()

Definition at line 544 of file qtcpserver.cpp.

◆ pauseAccepting()

void QTcpServer::pauseAccepting ( )

Since: 5.0

Pauses accepting new connections. Queued connections will remain in queue.

See also: resumeAccepting()

Definition at line 703 of file qtcpserver.cpp.

◆ pendingConnectionAvailable

void QTcpServer::pendingConnectionAvailable ( QPrivateSignal )

signal

This signal is emitted every time a new connection has been added to the pending connections queue.

See also: hasPendingConnections(), nextPendingConnection()

Since: 6.4

◆ proxy()

QNetworkProxy QTcpServer::proxy ( ) const

Since: 4.1

Returns the network proxy for this socket. By default QNetworkProxy::DefaultProxy is used.

See also: setProxy(), QNetworkProxy

Definition at line 747 of file qtcpserver.cpp.

◆ resumeAccepting()

void QTcpServer::resumeAccepting ( )

Since: 5.0

Resumes accepting new connections.

See also: pauseAccepting()

Definition at line 715 of file qtcpserver.cpp.

◆ serverAddress()

QHostAddress QTcpServer::serverAddress ( ) const

Returns the server's address if the server is listening for connections; otherwise returns QHostAddress::Null.

See also: serverPort(), listen()

Definition at line 469 of file qtcpserver.cpp.

◆ serverError()

QAbstractSocket::SocketError QTcpServer::serverError ( ) const

Returns an error code for the last error that occurred.

See also: errorString()

Definition at line 680 of file qtcpserver.cpp.

◆ serverPort()

quint16 QTcpServer::serverPort ( ) const

Returns the server's port if the server is listening for connections; otherwise returns 0.

See also: serverAddress(), listen()

Definition at line 456 of file qtcpserver.cpp.

◆ setListenBacklogSize()

void QTcpServer::setListenBacklogSize ( int size )

Sets the backlog queue size of to be accepted connections to size.

The operating system might reduce or ignore this value. By default, the queue size is 50.

Note: This property must be set prior to calling listen().

Since: 6.3

See also: listenBacklogSize()

Definition at line 658 of file qtcpserver.cpp.

◆ setMaxPendingConnections()

void QTcpServer::setMaxPendingConnections ( int numConnections )

Sets the maximum number of pending accepted connections to numConnections.

QTcpServer will accept no more than numConnections incoming connections before nextPendingConnection() is called. By default, the limit is 30 pending connections.

Clients may still able to connect after the server has reached its maximum number of pending connections (i.e., QTcpSocket can still emit the connected() signal). QTcpServer will stop accepting the new connections, but the operating system may still keep them in queue.

See also: maxPendingConnections(), hasPendingConnections()

Definition at line 631 of file qtcpserver.cpp.

◆ setProxy()

void QTcpServer::setProxy ( const QNetworkProxy & networkProxy )

Since: 4.1

Sets the explicit network proxy for this socket to networkProxy.

To disable the use of a proxy for this socket, use the QNetworkProxy::NoProxy proxy type:

server->setProxy(QNetworkProxy::NoProxy);

server

DBusConnection const char DBusError DBusBusType DBusError return DBusConnection DBusHandleMessageFunction void DBusFreeFunction return DBusConnection return DBusConnection return const char DBusError return DBusConnection DBusMessage dbus_uint32_t return DBusConnection dbus_bool_t DBusConnection DBusAddWatchFunction DBusRemoveWatchFunction DBusWatchToggledFunction void DBusFreeFunction return DBusConnection DBusDispatchStatusFunction void DBusFreeFunction DBusTimeout return DBusTimeout return DBusWatch return DBusWatch unsigned int return DBusError const DBusError return const DBusMessage return DBusMessage return DBusMessage return DBusMessage return DBusMessage return DBusMessage return DBusMessageIter int const void return DBusMessageIter DBusMessageIter return DBusMessageIter void DBusMessageIter void int return DBusMessage DBusMessageIter return DBusMessageIter return DBusMessageIter DBusMessageIter const char const char const char const char return DBusMessage return DBusMessage const char return DBusMessage dbus_bool_t return DBusMessage dbus_uint32_t return DBusMessage return DBusPendingCall DBusPendingCall return DBusPendingCall return dbus_int32_t return DBusServer * server

Definition qdbus_symbols_p.h:440

See also: proxy(), QNetworkProxy

Definition at line 733 of file qtcpserver.cpp.

◆ setSocketDescriptor()

bool QTcpServer::setSocketDescriptor ( qintptr socketDescriptor )

Sets the socket descriptor this server should use when listening for incoming connections to socketDescriptor.

Returns true if the socket is set successfully; otherwise returns false.

The socket is assumed to be in listening state.

See also: socketDescriptor(), isListening()

Definition at line 411 of file qtcpserver.cpp.

◆ socketDescriptor()

qintptr QTcpServer::socketDescriptor ( ) const

Returns the native socket descriptor the server uses to listen for incoming instructions, or -1 if the server is not listening.

If the server is using QNetworkProxy, the returned descriptor may not be usable with native socket functions.

See also: setSocketDescriptor(), isListening()

Definition at line 395 of file qtcpserver.cpp.

◆ waitForNewConnection()

bool QTcpServer::waitForNewConnection	(	int	msec = 0,
		bool *	timedOut = nullptr )

Waits for at most msec milliseconds or until an incoming connection is available.

Returns true if a connection is available; otherwise returns false. If the operation timed out and timedOut is not \nullptr, *timedOut will be set to true.

This is a blocking function call. Its use is disadvised in a single-threaded GUI application, since the whole application will stop responding until the function returns. waitForNewConnection() is mostly useful when there is no event loop available.

The non-blocking alternative is to connect to the newConnection() signal.

If msec is -1, this function will not time out.

See also: hasPendingConnections(), nextPendingConnection()

Definition at line 495 of file qtcpserver.cpp.

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

qtbase/src/network/socket/qtcpserver.h (782fbe0f63af5aeb583f84c28b7d0ff482bd28e4)
qtbase/src/network/socket/qtcpserver.cpp (032ffb70a829184fb620cf14fa146580b742e0e8)

Signals

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QTcpServer() [1/2]

◆ ~QTcpServer()

◆ QTcpServer() [2/2]

Member Function Documentation

◆ acceptError

◆ addPendingConnection()

◆ close()

◆ errorString()

◆ hasPendingConnections()

◆ incomingConnection()

◆ isListening()

◆ listen()

◆ listenBacklogSize()

◆ maxPendingConnections()

◆ newConnection

◆ nextPendingConnection()

◆ pauseAccepting()

◆ pendingConnectionAvailable

◆ proxy()

◆ resumeAccepting()

◆ serverAddress()

◆ serverError()

◆ serverPort()

◆ setListenBacklogSize()

◆ setMaxPendingConnections()

◆ setProxy()

◆ setSocketDescriptor()

◆ socketDescriptor()

◆ waitForNewConnection()