The QUdpSocket class provides a UDP socket. More...
#include <qudpsocket.h>
Public Member Functions inherited from Detailed Description
The QUdpSocket class provides a UDP socket.
\reentrant
\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:
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 56 of file qudpsocket.h.
Constructor & Destructor Documentation
◆ QUdpSocket()
Creates a QUdpSocket object.
parent is passed to the QObject constructor.
- See also
- socketType()
Definition at line 157 of file qudpsocket.cpp.
◆ ~QUdpSocket()
|
virtual |
Destroys the socket, closing the connection if necessary.
- See also
- close()
Definition at line 168 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 302 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 194 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 208 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 231 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 248 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 267 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 314 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.
Definition at line 494 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.
Definition at line 451 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.
Definition at line 284 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 341 of file qudpsocket.cpp.
◆ writeDatagram() [2/3]
|
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 89 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.
The function returns the number of bytes sent if it succeeded or -1 if it encountered an error.
- 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
- QNetworkDatagram::setDestination(), QNetworkDatagram::setHopLimit(), QNetworkDatagram::setInterfaceIndex()
Definition at line 406 of file qudpsocket.cpp.
The documentation for this class was generated from the following files:
- src/network/socket/qudpsocket.h
- src/network/socket/qudpsocket.cpp
