\reentrant More...

#include <qudpsocket.h>

Inheritance diagram for QUdpSocket:

Collaboration diagram for QUdpSocket:

Public Member Functions
	QUdpSocket (QObject *parent=nullptr)
	Creates a QUdpSocket object.
virtual	~QUdpSocket ()
	Destroys the socket, closing the connection if necessary.
bool	joinMulticastGroup (const QHostAddress &groupAddress)
bool	joinMulticastGroup (const QHostAddress &groupAddress, const QNetworkInterface &iface)
bool	leaveMulticastGroup (const QHostAddress &groupAddress)
bool	leaveMulticastGroup (const QHostAddress &groupAddress, const QNetworkInterface &iface)
QNetworkInterface	multicastInterface () const
void	setMulticastInterface (const QNetworkInterface &iface)
bool	hasPendingDatagrams () const
	Returns `true` if at least one datagram is waiting to be read; otherwise returns `false`.
qint64	pendingDatagramSize () const
	Returns the size of the first pending UDP datagram.
QNetworkDatagram	receiveDatagram (qint64 maxSize=-1)
qint64	readDatagram (char data, qint64 maxlen, QHostAddress host=nullptr, quint16 *port=nullptr)
	Receives a datagram no larger than maxSize bytes and stores it in data.
qint64	writeDatagram (const QNetworkDatagram &datagram)
qint64	writeDatagram (const char *data, qint64 len, const QHostAddress &host, quint16 port)
	Sends the datagram at data of size size to the host address address at port port.
qint64	writeDatagram (const QByteArray &datagram, const QHostAddress &host, quint16 port)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sends the datagram datagram to the host address host and at port port.
Public Member Functions inherited from QAbstractSocket
	QAbstractSocket (SocketType socketType, QObject *parent)
	Creates a new abstract socket of type socketType.
virtual	~QAbstractSocket ()
	Destroys the socket.
virtual void	resume ()
PauseModes	pauseMode () const
void	setPauseMode (PauseModes pauseMode)
virtual bool	bind (const QHostAddress &address, quint16 port=0, BindMode mode=DefaultForPlatform)
bool	bind (QHostAddress::SpecialAddress addr, quint16 port=0, BindMode mode=DefaultForPlatform)
bool	bind (quint16 port=0, BindMode mode=DefaultForPlatform)
virtual void	connectToHost (const QString &hostName, quint16 port, OpenMode mode=ReadWrite, NetworkLayerProtocol protocol=AnyIPProtocol)
	Attempts to make a connection to hostName on the given port.
void	connectToHost (const QHostAddress &address, quint16 port, OpenMode mode=ReadWrite)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Attempts to make a connection to address on port port.
virtual void	disconnectFromHost ()
	Attempts to close the socket.
bool	isValid () const
	Returns `true` if the socket is valid and ready for use; otherwise returns `false`.
qint64	bytesAvailable () const override
	Returns the number of incoming bytes that are waiting to be read.
qint64	bytesToWrite () const override
	Returns the number of bytes that are waiting to be written.
quint16	localPort () const
	Returns the host port number (in native byte order) of the local socket if available; otherwise returns 0.
QHostAddress	localAddress () const
	Returns the host address of the local socket if available; otherwise returns QHostAddress::Null.
quint16	peerPort () const
	Returns the port of the connected peer if the socket is in ConnectedState; otherwise returns 0.
QHostAddress	peerAddress () const
	Returns the address of the connected peer if the socket is in ConnectedState; otherwise returns QHostAddress::Null.
QString	peerName () const
	Returns the name of the peer as specified by connectToHost(), or an empty QString if connectToHost() has not been called.
qint64	readBufferSize () const
	Returns the size of the internal read buffer.
virtual void	setReadBufferSize (qint64 size)
	Sets the size of QAbstractSocket's internal read buffer to be size bytes.
void	abort ()
	Aborts the current connection and resets the socket.
virtual qintptr	socketDescriptor () const
	Returns the native socket descriptor of the QAbstractSocket object if this is available; otherwise returns -1.
virtual bool	setSocketDescriptor (qintptr socketDescriptor, SocketState state=ConnectedState, OpenMode openMode=ReadWrite)
	Initializes QAbstractSocket with the native socket descriptor socketDescriptor.
virtual void	setSocketOption (QAbstractSocket::SocketOption option, const QVariant &value)
virtual QVariant	socketOption (QAbstractSocket::SocketOption option)
SocketType	socketType () const
	Returns the socket type (TCP, UDP, or other).
SocketState	state () const
	Returns the state of the socket.
SocketError	error () const
	Returns the type of error that last occurred.
void	close () override
	Closes the I/O device for the socket and calls disconnectFromHost() to close the socket's connection.
bool	isSequential () const override
	\reimp
bool	flush ()
	This function writes as much as possible from the internal write buffer to the underlying network socket, without blocking.
virtual bool	waitForConnected (int msecs=30000)
	Waits until the socket is connected, up to msecs milliseconds.
bool	waitForReadyRead (int msecs=30000) override
	This function blocks until new data is available for reading and the \l{QIODevice::}{readyRead()} signal has been emitted.
bool	waitForBytesWritten (int msecs=30000) override
	\reimp
virtual bool	waitForDisconnected (int msecs=30000)
	Waits until the socket has disconnected, up to msecs milliseconds.
void	setProxy (const QNetworkProxy &networkProxy)
QNetworkProxy	proxy () const
QString	protocolTag () const
void	setProtocolTag (const QString &tag)

Additional Inherited Members
Public Types inherited from QAbstractSocket
enum	SocketType { TcpSocket , UdpSocket , SctpSocket , UnknownSocketType = -1 }
	This enum describes the transport layer protocol. More...
enum	SocketError { ConnectionRefusedError , RemoteHostClosedError , HostNotFoundError , SocketAccessError , SocketResourceError , SocketTimeoutError , DatagramTooLargeError , NetworkError , AddressInUseError , SocketAddressNotAvailableError , UnsupportedSocketOperationError , UnfinishedSocketOperationError , ProxyAuthenticationRequiredError , SslHandshakeFailedError , ProxyConnectionRefusedError , ProxyConnectionClosedError , ProxyConnectionTimeoutError , ProxyNotFoundError , ProxyProtocolError , OperationError , SslInternalError , SslInvalidUserDataError , TemporaryError , UnknownSocketError = -1 }
	This enum describes the socket errors that can occur. More...
enum	SocketState { UnconnectedState , HostLookupState , ConnectingState , ConnectedState , BoundState , ListeningState , ClosingState }
	This enum describes the different states in which a socket can be. More...
enum	SocketOption { LowDelayOption , KeepAliveOption , MulticastTtlOption , MulticastLoopbackOption , TypeOfServiceOption , SendBufferSizeSocketOption , ReceiveBufferSizeSocketOption , PathMtuSocketOption }
enum	BindFlag { DefaultForPlatform = 0x0 , ShareAddress = 0x1 , DontShareAddress = 0x2 , ReuseAddressHint = 0x4 }
enum	PauseMode { PauseNever = 0x0 , PauseOnSslErrors = 0x1 }
Public Types inherited from QtPrivate::QAbstractSocketConstants
using	NetworkLayerProtocol = QHostAddress::NetworkLayerProtocol
Signals inherited from QAbstractSocket
void	hostFound ()
	This signal is emitted after connectToHost() has been called and the host lookup has succeeded.
void	connected ()
	This signal is emitted after connectToHost() has been called and a connection has been successfully established.
void	disconnected ()
	This signal is emitted when the socket has been disconnected.
void	stateChanged (QAbstractSocket::SocketState)
	This signal is emitted whenever QAbstractSocket's state changes.
void	errorOccurred (QAbstractSocket::SocketError)
void	proxyAuthenticationRequired (const QNetworkProxy &proxy, QAuthenticator *authenticator)
Static Public Attributes inherited from QtPrivate::QAbstractSocketConstants
static constexpr auto	IPv4Protocol = QHostAddress::IPv4Protocol
static constexpr auto	IPv6Protocol = QHostAddress::IPv6Protocol
static constexpr auto	AnyIPProtocol = QHostAddress::AnyIPProtocol
static constexpr auto	UnknownNetworkLayerProtocol = QHostAddress::UnknownNetworkLayerProtocol
Protected Member Functions inherited from QAbstractSocket
qint64	readData (char *data, qint64 maxlen) override
	\reimp
qint64	readLineData (char *data, qint64 maxlen) override
	\reimp
qint64	skipData (qint64 maxSize) override
	\reimp
qint64	writeData (const char *data, qint64 len) override
	\reimp
void	setSocketState (SocketState state)
	Sets the state of the socket to state.
void	setSocketError (SocketError socketError)
	Sets the type of error that last occurred to socketError.
void	setLocalPort (quint16 port)
void	setLocalAddress (const QHostAddress &address)
void	setPeerPort (quint16 port)
void	setPeerAddress (const QHostAddress &address)
void	setPeerName (const QString &name)
	QAbstractSocket (SocketType socketType, QAbstractSocketPrivate &dd, QObject *parent=nullptr)

Detailed Description

\reentrant

The QUdpSocket class provides a UDP socket.

\inmodule QtNetwork

UDP (User Datagram Protocol) is a lightweight, unreliable, datagram-oriented, connectionless protocol. It can be used when reliability isn't 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() / receiveDatagram() 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 don't 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() or receiveDatagram() 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.

Example:

void Server::initSocket()
{
    udpSocket = new QUdpSocket(this);
    udpSocket->bind(QHostAddress::LocalHost, 7755);
 
    connect(udpSocket, &QUdpSocket::readyRead,
            this, &Server::readPendingDatagrams);
}
 
void Server::readPendingDatagrams()
{
    while (udpSocket->hasPendingDatagrams()) {
        QNetworkDatagram datagram = udpSocket->receiveDatagram();
        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.

The \l{broadcastsender}{Broadcast Sender}, \l{broadcastreceiver}{Broadcast Receiver}, \l{multicastsender}{Multicast Sender}, and \l{multicastreceiver}{Multicast Receiver} examples illustrate how to use QUdpSocket in applications.

See also: QTcpSocket, QNetworkDatagram

Definition at line 21 of file qudpsocket.h.

Constructor & Destructor Documentation

◆ QUdpSocket()

QUdpSocket::QUdpSocket ( QObject * parent = nullptr )

explicit

Creates a QUdpSocket object.

parent is passed to the QObject constructor.

See also: socketType()

Definition at line 122 of file qudpsocket.cpp.

◆ ~QUdpSocket()

QUdpSocket::~QUdpSocket ( )

virtual

Destroys the socket, closing the connection if necessary.

See also: close()

Definition at line 133 of file qudpsocket.cpp.

Member Function Documentation

◆ hasPendingDatagrams()

bool QUdpSocket::hasPendingDatagrams ( ) const

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

See also: pendingDatagramSize(), readDatagram()

Definition at line 267 of file qudpsocket.cpp.

◆ joinMulticastGroup() [1/2]

bool QUdpSocket::joinMulticastGroup ( const QHostAddress & groupAddress )

Since: 4.8

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.

Note that if you are attempting to join an IPv4 group, your socket must not be bound using IPv6 (or in dual mode, using QHostAddress::Any). You must use QHostAddress::AnyIPv4 instead.

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

Note: Joining IPv6 multicast groups without an interface selection is not supported in all operating systems. Consider using the overload where the interface is specified.

See also: leaveMulticastGroup()

Definition at line 159 of file qudpsocket.cpp.

◆ joinMulticastGroup() [2/2]

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

Since: 4.8 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Joins the multicast group address groupAddress on the interface iface.

See also: leaveMulticastGroup()

Definition at line 173 of file qudpsocket.cpp.

◆ leaveMulticastGroup() [1/2]

bool QUdpSocket::leaveMulticastGroup ( const QHostAddress & groupAddress )

Since: 4.8

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.

Note: This function should be called with the same arguments as were passed to joinMulticastGroup().

See also: joinMulticastGroup()

Definition at line 196 of file qudpsocket.cpp.

◆ leaveMulticastGroup() [2/2]

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

Since: 4.8 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

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

Note: This function should be called with the same arguments as were passed to joinMulticastGroup().

See also: joinMulticastGroup()

Definition at line 213 of file qudpsocket.cpp.

◆ multicastInterface()

QNetworkInterface QUdpSocket::multicastInterface ( ) const

Since: 4.8

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()

Definition at line 232 of file qudpsocket.cpp.

◆ pendingDatagramSize()

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()

Definition at line 279 of file qudpsocket.cpp.

◆ readDatagram()

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

Receives a datagram no larger than maxSize bytes and stores it in data.

The sender's host address and port is stored in address and *port (unless the pointers are \nullptr).

Returns the size of the datagram on success; otherwise returns -1.

If maxSize 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 maxSize is 0, the datagram will be discarded.

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

Definition at line 460 of file qudpsocket.cpp.

◆ receiveDatagram()

QNetworkDatagram QUdpSocket::receiveDatagram ( qint64 maxSize = -1 )

Since: 5.8

Receives a datagram no larger than maxSize bytes and returns it in the QNetworkDatagram object, along with the sender's host address and port. If possible, this function will also try to determine the datagram's destination address, port, and the number of hop counts at reception time.

On failure, returns a QNetworkDatagram that reports \l {QNetworkDatagram::isValid()}{not valid}.

If maxSize is too small, the rest of the datagram will be lost. If maxSize is 0, the datagram will be discarded. If maxSize is -1 (the default), this function will attempt to read the entire datagram.

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

Definition at line 416 of file qudpsocket.cpp.

◆ setMulticastInterface()

void QUdpSocket::setMulticastInterface ( const QNetworkInterface & iface )

Since: 4.8

Sets the outgoing interface for multicast datagrams to the interface iface. 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()

Definition at line 249 of file qudpsocket.cpp.

◆ writeDatagram() [1/3]

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

Sends the datagram at data of size size to the host address address at port 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 function 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()

Definition at line 306 of file qudpsocket.cpp.

◆ writeDatagram() [2/3]

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

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sends the datagram datagram to the host address host and at port port.

The function returns the number of bytes sent if it succeeded or -1 if it encountered an error.

Definition at line 54 of file qudpsocket.h.

◆ writeDatagram() [3/3]

qint64 QUdpSocket::writeDatagram ( const QNetworkDatagram & datagram )

Since: 5.8 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Sends the datagram datagram to the host address and port numbers contained in datagram, using the network interface and hop count limits also set there. If the destination address and port numbers are unset, this function will send to the address that was passed to connectToHost().

If the destination address is IPv6 with a non-empty \l{QHostAddress::scopeId()}{scope id} but differs from the interface index in datagram, it is undefined which interface the operating system will choose to send on.