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QT notes - qudpsocket of network communication
2022-07-22 18:11:00 【Cool breeze in the old street °】
UDP( User datagram protocol ), It's a light weight , unreliable , Datagram oriented , Connectionless Protocols . When the reliability of communication requirements is not important （ Data may be lost ）, It can be used UDP signal communication
.pro Add a network module to the file QT += network
The header file ：#include<QUdpSocket>
Important functions ：
bind() // Server binding port
hasPendingDatagrams() // When data comes , At least one datagram needs to be read .
writeDatagram(const char *data, qint64 size, const QHostAddress &address, quint16 port) // Function to the specified address host And port port Send datagram datagram, Returns the number of bytes successfully sent , Datagrams should not be too long , Not more than 512Byte
readDatagram(char *data, qint64 maxSize, QHostAddress *address = nullptr, quint16 *port = nullptr)
pendingDatagramSize() // Function the size of the first datagram to be read Byte.
joinMulticastGroup() // Function to make socket Join a multicast group groupAddress.
leaveMulticastGroup() // Function to make socket Leave the multicast group groupAddress.
Design it. UI：
The server ：
1. Binding port
m_udpSocket->bind(QHostAddress::AnyIPv4,8888);
2. Send a message and Read message
2.1 Send a message
// pick up information
QString sendStr = ui.sendTextEdit->toPlainText();
quint16 port = ui.portLineEdit->text().toInt();
QString ip = ui.IPlineEdit->text();
m_udpSocket->writeDatagram(sendStr.toUtf8(), QHostAddress(ip), port);
// Connect socket Read the message sent
connect(m_udpSocket, &QUdpSocket::readyRead, this, &QUdpTest::readValue);
2.2 Read message
while (m_udpSocket->hasPendingDatagrams())
{
QByteArray array;
//array.resize(m_udpSocket->bytesAvailable());
array.resize(m_udpSocket->pendingDatagramSize());
QHostAddress address;
quint16 port;
m_udpSocket->readDatagram(array.data(), array.size(),&address,&port);
qDebug() << QStringLiteral(" The size passed is ：") << array.size();
// Read data stream with
//QDataStream read(&array, QIODevice::ReadOnly);
//Person p;
//read >> p.age >> p.score ;
//read.readRawData(p.name, sizeof(p.name));
//QString str = QString("%1 %2 %3").arg(QString::number(p.age)).arg(p.name).arg(QString::number(p.score));
qDebug() << array.data();
// Read the structure sent （ Strong transformation into the structure we need to transform ）
Person* p = reinterpret_cast<Person*>(array.data());
QString str1 = QString(QLatin1String(p->name));
QString str = QString("%1 %2 %3").arg(QString::number(p->age)).arg(str1).arg(QString::number(p->score));
ui.recvTextEdit->setText(str);
}
client ：
1. Binding port
m_socket->bind(QHostAddress::AnyIPv4,9999);
2. Send a message and Read message
2.1 Send a message
quint16 port = ui.portLineEdit->text().toInt();
QString ip = ui.IPLineEdit->text();
QString sendStr = ui.sendTextEdit->toPlainText();
Person p1;
strcpy(p1.name, "xm");
p1.age = 20;
p1.score = 60;
// Sending data streams
//QByteArray text_data;
//QDataStream write(&text_data, QIODevice::WriteOnly);
//write << p1.age << p1.score ;
//write.writeRawData(p1.name, 20);
//m_socket->writeDatagram(text_data, text_data.size(), QHostAddress(ip), port);
// Send the contents in the input box
//m_socket->writeDatagram(sendStr.toUtf8(),QHostAddress(ip), port);
//m_socket->writeDatagram(sendStr.toLocal8Bit(), sendStr.size(), QHostAddress(ip), port);
// Send structure
m_socket->writeDatagram(( char*)&p1, sizeof(Person), QHostAddress(ip), port);
qDebug() << QStringLiteral(" Size of data sent ：") << sizeof(p1);
2.2 Read message
while (m_socket->hasPendingDatagrams())
{
QByteArray array;
//array.resize(m_socket->bytesAvailable());// Set the space size according to the readable data
array.resize(m_socket->pendingDatagramSize());
QHostAddress address;
quint16 port;
m_socket->readDatagram(array.data(), array.size(), &address, &port);
// Display Chinese without garbled code
ui.recvTextEdit->setText(QString::fromLocal8Bit(array.data()) );
}
3. Both client and server join multicast
UDP Multicast is a one-to-one communication mode between hosts , When multiple clients join a multicast group defined by a multicast address , The client sends to this multicast address and port UDP The datagram , Members of the group can receive .
m_socket->joinMulticastGroup(QHostAddress("224.0.0.100"));
Complete code ：
QUdpTest.h
#pragma once
#include <QtWidgets/QWidget>
#include "ui_QUdpTest.h"
#include <QUdpSocket>
#include <QDebug>
class QUdpTest : public QWidget
{
Q_OBJECT
struct Person
{
char name[20];
int age;
int score;
Person()
{
memset(name, 0, 20);
age = 0;
score = 0;
}
};
public:
QUdpTest(QWidget *parent = Q_NULLPTR);
~QUdpTest();
public slots:
void readValue();
void on_sendBtn_clicked();
void on_delBtn_clicked();
private:
Ui::QUdpTestClass ui;
QUdpSocket* m_udpSocket;
};
QUdpTest.cpp
#include "QUdpTest.h"
#include <QDebug>
#include <QByteArray>
#include <QString>
#include <QLatin1String>
QUdpTest::QUdpTest(QWidget *parent)
: QWidget(parent)
{
ui.setupUi(this);
m_udpSocket = new QUdpSocket(this);
this->setWindowTitle(QStringLiteral(" The binding port number is ：8888"));
// Binding port
m_udpSocket->bind(QHostAddress::AnyIPv4,8888);
m_udpSocket->joinMulticastGroup(QHostAddress("224.0.0.100"));
connect(m_udpSocket, &QUdpSocket::readyRead, this, &QUdpTest::readValue);
ui.recvTextEdit->setReadOnly(true);
}
QUdpTest::~QUdpTest()
{
}
void QUdpTest::readValue()
{
while (m_udpSocket->hasPendingDatagrams())
{
QByteArray array;
//array.resize(m_udpSocket->bytesAvailable());
array.resize(m_udpSocket->pendingDatagramSize());
QHostAddress address;
quint16 port;
m_udpSocket->readDatagram(array.data(), array.size(),&address,&port);
qDebug() << QStringLiteral(" The size passed is ：") << array.size();
//QDataStream read(&array, QIODevice::ReadOnly); // Read data stream
//Person p;
//read >> p.age >> p.score ;
//read.readRawData(p.name, sizeof(p.name));
//QString str = QString("%1 %2 %3").arg(QString::number(p.age)).arg(p.name).arg(QString::number(p.score));
qDebug() << array.data();
Person* p = reinterpret_cast<Person*>(array.data());
QString str1 = QString(QLatin1String(p->name));
QString str = QString("%1 %2 %3").arg(QString::number(p->age)).arg(str1).arg(QString::number(p->score));
ui.recvTextEdit->setText(str);
}
}
void QUdpTest::on_sendBtn_clicked()
{
// pick up information
QString sendStr = ui.sendTextEdit->toPlainText();
quint16 port = ui.portLineEdit->text().toInt();
QString ip = ui.IPlineEdit->text();
m_udpSocket->writeDatagram(sendStr.toUtf8(), QHostAddress(ip), port);
}
void QUdpTest::on_delBtn_clicked()
{
m_udpSocket->leaveMulticastGroup(QHostAddress("224.0.0.100"));
}
QUdpTest1.h
#pragma once
#include <QWidget>
#include "ui_QUdpTest1.h"
#include <QUdpSocket>
class QUdpTest1 : public QWidget
{
Q_OBJECT
struct Person
{
char name[20];
int age;
int score;
Person()
{
memset(name, 0, 20);
age = 0;
score = 0;
}
};
public:
QUdpTest1(QWidget *parent = Q_NULLPTR);
~QUdpTest1();
public slots:
void readValue();
void on_sendBtn_clicked();
void on_delBtn_clicked();
private:
Ui::QUdpTest1 ui;
QUdpSocket* m_socket;
};
QUdpTest1.cpp
#include "QUdpTest1.h"
#include <string.h>
QUdpTest1::QUdpTest1(QWidget *parent)
: QWidget(parent)
{
ui.setupUi(this);
m_socket = new QUdpSocket(this);
this->setWindowTitle(QStringLiteral(" The binding port is ：9999"));
m_socket->bind(QHostAddress::AnyIPv4,9999);
m_socket->joinMulticastGroup(QHostAddress("224.0.0.100"));
connect(m_socket, &QUdpSocket::readyRead, this, &QUdpTest1::readValue);
ui.recvTextEdit->setReadOnly(true);
}
QUdpTest1::~QUdpTest1()
{
}
void QUdpTest1::readValue()
{
while (m_socket->hasPendingDatagrams())
{
QByteArray array;
//array.resize(m_socket->bytesAvailable());// Set the space size according to the readable data
array.resize(m_socket->pendingDatagramSize());
QHostAddress address;
quint16 port;
m_socket->readDatagram(array.data(), array.size(), &address, &port);
ui.recvTextEdit->setText(array);
}
}
void QUdpTest1::on_sendBtn_clicked()
{
quint16 port = ui.portLineEdit->text().toInt();
QString ip = ui.IPLineEdit->text();
QString sendStr = ui.sendTextEdit->toPlainText();
Person p1;
strcpy(p1.name, "xm");
p1.age = 20;
p1.score = 60;
//QByteArray text_data;
//QDataStream write(&text_data, QIODevice::WriteOnly);
//write<< p1.age << p1.score ;
//write.writeRawData(p1.name, sizeof(p1.name));
//m_socket->writeDatagram(text_data, text_data.size(), QHostAddress(ip), port);
//m_socket->writeDatagram(sendStr.toUtf8(),QHostAddress(ip), port);
//m_socket->writeDatagram(sendStr.toLocal8Bit(), sendStr.size(), QHostAddress(ip), port);
m_socket->writeDatagram(( char*)&p1, sizeof(Person), QHostAddress(ip), port);
qDebug() << QStringLiteral(" Size of data sent ：") << sizeof(p1);
}
void QUdpTest1::on_delBtn_clicked()
{
m_socket->leaveMulticastGroup(QHostAddress("224.0.0.100"));
}
Running results ：
Send the content in the text ：
Send the content in the structure ：
Reference blog ：
QT Network programming UDP
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