The QUdpSocket class provides a UDP socket. More...

Inheritance diagram for QUdpSocket:

Public Methods
	QUdpSocket (QObject *parent=nullptr)

virtual	~QUdpSocket ()

bool	hasPendingDatagrams () const

bool	joinMulticastGroup (const QHostAddress &groupAddress)

bool	joinMulticastGroup (const QHostAddress &groupAddress, const QNetworkInterface &interfaceId)

bool	leaveMulticastGroup (const QHostAddress &groupAddress)

bool	leaveMulticastGroup (const QHostAddress &groupAddress, const QNetworkInterface &interfaceId)

QNetworkInterface	multicastInterface () const

qint64	pendingDatagramSize () const

qint64	readDatagram (char data, qint64 maxlen, QHostAddress address=nullptr, quint16 *port=nullptr)

void	setMulticastInterface (const QNetworkInterface &interfaceId)

qint64	writeDatagram (const char *data, qint64 len, const QHostAddress &address, quint16 port)

qint64	writeDatagram (const QByteArray &datagram, const QHostAddress &address, quint16 port)

Public Methods inherited from QAbstractSocket
	QAbstractSocket (SocketType socketType, QObject *parent)

virtual	~QAbstractSocket ()

void	abort ()

bool	atEnd () const override

bool	bind (const QHostAddress &address, quint16 port=0, BindMode mode=DefaultForPlatform)

bool	bind (quint16 port=0, BindMode mode=DefaultForPlatform)

qint64	bytesAvailable () const override

qint64	bytesToWrite () const override

bool	canReadLine () const override

void	close () override

virtual void	connectToHost (const QHostAddress &address, quint16 port, OpenMode openMode=ReadWrite)

virtual void	connectToHost (const QString &hostName, quint16 port, OpenMode openMode=ReadWrite, NetworkLayerProtocol protocol=AnyIPProtocol)

virtual void	disconnectFromHost ()

SocketError	error () const

bool	flush ()

bool	isSequential () const override

bool	isValid () const

QHostAddress	localAddress () const

quint16	localPort () const

PauseModes	pauseMode () const

QHostAddress	peerAddress () const

QString	peerName () const

quint16	peerPort () const

QNetworkProxy	proxy () const

qint64	readBufferSize () const

virtual void	resume ()

void	setPauseMode (PauseModes pauseMode)

void	setProxy (const QNetworkProxy &networkProxy)

virtual void	setReadBufferSize (qint64 size)

virtual bool	setSocketDescriptor (qintptr socketDescriptor, SocketState socketState=ConnectedState, OpenMode openMode=ReadWrite)

virtual void	setSocketOption (QAbstractSocket::SocketOption option, const QVariant &value)

virtual qintptr	socketDescriptor () const

virtual QVariant	socketOption (QAbstractSocket::SocketOption option)

SocketType	socketType () const

SocketState	state () const

bool	waitForBytesWritten (int msecs=30000) override

virtual bool	waitForConnected (int msecs=30000)

virtual bool	waitForDisconnected (int msecs=30000)

bool	waitForReadyRead (int msecs=30000) override

Public Methods inherited from QIODevice
	QIODevice ()

	QIODevice (QObject *parent)

virtual	~QIODevice ()

QString	errorString () const

bool	getChar (char *c)

bool	isOpen () const

bool	isReadable () const

bool	isTextModeEnabled () const

bool	isWritable () const

virtual bool	open (OpenMode mode)

OpenMode	openMode () const

qint64	peek (char *data, qint64 maxSize)

QByteArray	peek (qint64 maxSize)

virtual qint64	pos () const

bool	putChar (char c)

qint64	read (char *data, qint64 maxSize)

QByteArray	read (qint64 maxSize)

QByteArray	readAll ()

qint64	readLine (char *data, qint64 maxSize)

QByteArray	readLine (qint64 maxSize=0)

virtual bool	reset ()

virtual bool	seek (qint64 pos)

void	setTextModeEnabled (bool enabled)

virtual qint64	size () const

void	ungetChar (char c)

qint64	write (const char *data)

qint64	write (const char *data, qint64 maxSize)

qint64	write (const QByteArray &data)

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Additional Inherited Members
Public Typedefs inherited from QAbstractSocket
using	BindMode = QFlags< BindFlag >

using	PauseModes = QFlags< PauseMode >

Public Typedefs inherited from QIODevice
using	OpenMode = QFlags< OpenModeFlag >

Public Types inherited from QAbstractSocket
enum	BindFlag

enum	NetworkLayerProtocol

enum	PauseMode

enum	SocketError

enum	SocketOption

enum	SocketState

enum	SocketType

Public Types inherited from QIODevice
enum	OpenModeFlag

Public Signals inherited from QAbstractSocket
void	connected ()

void	disconnected ()

void	error (QAbstractSocket::SocketError socketError)

void	hostFound ()

void	proxyAuthenticationRequired (const QNetworkProxy &proxy, QAuthenticator *authenticator)

void	stateChanged (QAbstractSocket::SocketState socketState)

Public Signals inherited from QIODevice
void	aboutToClose ()

void	bytesWritten (qint64 bytes)

void	readChannelFinished ()

void	readyRead ()

Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Public Slots inherited from QObject
void	deleteLater ()

Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Protected Methods inherited from QAbstractSocket
qint64	readData (char *data, qint64 maxlen) override

qint64	readLineData (char *data, qint64 maxlen) override

void	setLocalAddress (const QHostAddress &address)

void	setLocalPort (quint16 port)

void	setPeerAddress (const QHostAddress &address)

void	setPeerName (const QString &name)

void	setPeerPort (quint16 port)

void	setSocketError (SocketError socketError)

void	setSocketState (SocketState state)

qint64	writeData (const char *data, qint64 len) override

Protected Methods inherited from QIODevice
void	setErrorString (const QString &errorString)

void	setOpenMode (OpenMode openMode)

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Properties inherited from QObject
	objectName

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

The QUdpSocket class provides a UDP socket.

UDP (User Datagram Protocol) is a lightweight, unreliable, datagram-oriented, connectionless protocol. It can be used when reliability is not important. QUdpSocket is a subclass of QAbstractSocket that allows you to send and receive UDP datagrams.

The most common way to use this class is to bind to an address and port using bind(), then call writeDatagram() and readDatagram() to transfer data. If you want to use the standard QIODevice functions read(), readLine(), write(), etc., you must first connect the socket directly to a peer by calling connectToHost().

The socket emits the bytesWritten() signal every time a datagram is written to the network. If you just want to send datagrams, you do not need to call bind().

The readyRead() signal is emitted whenever datagrams arrive. In that case, hasPendingDatagrams() returns true. Call pendingDatagramSize() to obtain the size of the first pending datagram, and readDatagram() to read it.

Note: An incoming datagram should be read when you receive the readyRead() signal, otherwise this signal will not be emitted for the next datagram.

void Server::initSocket()
{
    udpSocket = new QUdpSocket(this);
    udpSocket->bind(QHostAddress::LocalHost, 7755);
 
    connect(udpSocket, SIGNAL(readyRead()), this, SLOT(readPendingDatagrams()));
}
 
void Server::readPendingDatagrams()
{
    while (udpSocket->hasPendingDatagrams()) {
        QByteArray datagram;
        datagram.resize(udpSocket->pendingDatagramSize());
 
        QHostAddress sender;
        quint16 senderPort;
 
        udpSocket->readDatagram(datagram.data(), datagram.size(), &sender, &senderPort);
 
        processTheDatagram(datagram);
    }
}

QUdpSocket also supports UDP multicast. Use joinMulticastGroup() and leaveMulticastGroup() to control group membership, and QAbstractSocket::MulticastTtlOption and QAbstractSocket::MulticastLoopbackOption to set the TTL and loopback socket options. Use setMulticastInterface() to control the outgoing interface for multicast datagrams, and multicastInterface() to query it.

With QUdpSocket, you can also establish a virtual connection to a UDP server using connectToHost() and then use read() and write() to exchange datagrams without specifying the receiver for each datagram.

See also: QTcpSocket

Constructor & Destructor Documentation

QUdpSocket::QUdpSocket ( QObject * parent = nullptr )

explicit

Creates a QUdpSocket object.

parent is passed to the QObject constructor.

See also: socketType()

QUdpSocket::~QUdpSocket ( )

virtual

Destroys the socket, closing the connection if necessary.

See also: close()

Method Documentation

bool QUdpSocket::hasPendingDatagrams ( ) const

Returns true if at least one datagram is waiting to be read, otherwise returns false.

See also: pendingDatagramSize(), readDatagram()

bool QUdpSocket::joinMulticastGroup ( const QHostAddress & groupAddress )

Joins the multicast group specified by groupAddress on the default interface chosen by the operating system. The socket must be in BoundState, otherwise an error occurs. This method returns true if successful, otherwise it returns false and sets the socket error accordingly.

See also: leaveMulticastGroup()

bool QUdpSocket::joinMulticastGroup	(	const QHostAddress &	groupAddress,
		const QNetworkInterface &	interfaceId
	)

Joins the multicast group address groupAddress on the interface interfaceId.

See also: leaveMulticastGroup()

bool QUdpSocket::leaveMulticastGroup ( const QHostAddress & groupAddress )

Leaves the multicast group specified by groupAddress on the default interface chosen by the operating system. The socket must be in BoundState, otherwise an error occurs.

This function returns true if successful, otherwise it returns false and sets the socket error accordingly.

See also: joinMulticastGroup()

bool QUdpSocket::leaveMulticastGroup	(	const QHostAddress &	groupAddress,
		const QNetworkInterface &	interfaceId
	)

Leaves the multicast group specified by groupAddress on the interface interfaceId.

See also: joinMulticastGroup()

QNetworkInterface QUdpSocket::multicastInterface ( ) const

Returns the interface for the outgoing interface for multicast datagrams. This corresponds to the IP_MULTICAST_IF socket option for IPv4 sockets and the IPV6_MULTICAST_IF socket option for IPv6 sockets. If no interface has been previously set, this function returns an invalid QNetworkInterface. The socket must be in BoundState, otherwise an invalid QNetworkInterface is returned.

See also: setMulticastInterface()

qint64 QUdpSocket::pendingDatagramSize ( ) const

Returns the size of the first pending UDP datagram. If there is no datagram available, this function returns -1.

See also: hasPendingDatagrams(), readDatagram()

qint64 QUdpSocket::readDatagram	(	char *	data,
		qint64	maxlen,
		QHostAddress *	address = `nullptr`,
		quint16 *	port = `nullptr`
	)

Receives a datagram no larger than maxlen bytes and stores it in data. The sender's host address and port is stored in address and port, unless the pointers are null. Returns the size of the datagram on success, otherwise returns -1.

If maxlen is too small, the rest of the datagram will be lost. To avoid loss of data, call pendingDatagramSize() to determine the size of the pending datagram before attempting to read it. If maxlen is 0 the datagram will be discarded.

See also: writeDatagram(), hasPendingDatagrams(), pendingDatagramSize()

void QUdpSocket::setMulticastInterface ( const QNetworkInterface & interfaceId )

Sets the outgoing interface for multicast datagrams to the interfaceId. This corresponds to the IP_MULTICAST_IF socket option for IPv4 sockets and the IPV6_MULTICAST_IF socket option for IPv6 sockets. The socket must be in BoundState, otherwise this function does nothing.

See also: multicastInterface(), joinMulticastGroup(), leaveMulticastGroup()

qint64 QUdpSocket::writeDatagram	(	const char *	data,
		qint64	len,
		const QHostAddress &	address,
		quint16	port
	)

Sends the datagram at data of size len to the host address at port. Returns the number of bytes sent on success, otherwise returns -1.

Datagrams are always written as one block. The maximum size of a datagram is highly platform-dependent, but can be as low as 8192 bytes. If the datagram is too large, this function will return -1 and error() will return DatagramTooLargeError.

Sending datagrams larger than 512 bytes is in general disadvised, as even if they are sent successfully, they are likely to be fragmented by the IP layer before arriving at their final destination.

Warning: Calling this method on a connected UDP socket may result in an error and no packet being sent. If you are using a connected socket, use write() to send datagrams.

See also: readDatagram(), write()

qint64 QUdpSocket::writeDatagram	(	const QByteArray &	datagram,
		const QHostAddress &	address,
		quint16	port
	)

inline

Sends the datagram to the host address at the given port.

Public Methods

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Method Documentation