一、知识点总结

udpSocket->bind(8888); //绑定端口

connect(udpSocket,&QUdpSocket::readyRead,this,&UdpA::dealMsg); //收到对方的消息，立即触发

char buf[1024] = {0};//缓存

QHostAddress peerIp; //对方IP

quint16 peerPort; //对方端口

qint16 length = udpSocket->readDatagram(buf,sizeof(buf),&peerIp,&peerPort);// 读到多少个字符

QString("[%1:%2] %3").arg(peerIp.toString()).arg(peerPort).arg(buf);  //字符串模板占位

QString ip = ui->ip->text();　　　　　　 

qint16 port = ui->port->text().toInt();　　　//端口号

QString msg = ui->msg->toPlainText();  //输入框内容

udpSocket->writeDatagram(msg.toUtf8().data(),QHostAddress(ip),port);// 写出字符串

二、案例

1、UdpA

UdpA.h

#ifndef UDPA_H
#define UDPA_H

#include <QWidget>
#include <QUdpSocket>

QT_BEGIN_NAMESPACE
namespace Ui { class UdpA; }
QT_END_NAMESPACE

class UdpA : public QWidget
{
    Q_OBJECT

public:
    UdpA(QWidget *parent = nullptr);
    ~UdpA();
    void dealMsg(); //槽函数，处理对方发过来的消息

private slots:
    void on_pushButton_clicked();

private:
    Ui::UdpA *ui;
    QUdpSocket * udpSocket;
};
#endif // UDPA_H

UdpA.cpp

#include "UdpA.h"
#include "ui_UdpA.h"

UdpA::UdpA(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::UdpA)
{
    ui->setupUi(this);
    setWindowTitle("UdpA:8888");

    //分配空间，指定父对象，自动释放内存
    udpSocket = new QUdpSocket(this);
    //绑定端口
    udpSocket->bind(8888);

    //收到对方的消息，立即触发
    connect(udpSocket,&QUdpSocket::readyRead,this,&UdpA::dealMsg);
}

UdpA::~UdpA()
{
    delete ui;
}

//处理对方发过来的内容
void UdpA::dealMsg()
{
    char buf[1024] = {0}; //缓存
    QHostAddress peerIp; //对方IP
    quint16 peerPort; //对方端口
    qint16 length = udpSocket->readDatagram(buf,sizeof(buf),&peerIp,&peerPort);//读到多少个字符
    if(length>0){
        QString msgTxt = QString("[%1:%2] %3")
                .arg(peerIp.toString())
                .arg(peerPort)
                .arg(buf); //字符串模板占位
        ui->msg->setText(msgTxt);
    }
}


void UdpA::on_pushButton_clicked()
{
    //获取对方的IP和端口
    QString ip = ui->ip->text();
    qint16 port = ui->port->text().toInt();
    QString msg = ui->msg->toPlainText();
    udpSocket->writeDatagram(msg.toUtf8().data(),QHostAddress(ip),port);
}

2、UdpB

UdpB.h

#ifndef UDPB_H
#define UDPB_H

#include <QWidget>
#include <QUdpSocket>

namespace Ui {
class UdpB;
}

class UdpB : public QWidget
{
    Q_OBJECT

public:
    explicit UdpB(QWidget *parent = nullptr);
    ~UdpB();

private slots:
    void on_pushButton_clicked();

    void dealMsg();

private:
    Ui::UdpB *ui;
    QUdpSocket * udpSocket;
};

#endif // UDPB_H

UdpB.cpp

#include "UdpB.h"
#include "ui_UdpB.h"

UdpB::UdpB(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::UdpB)
{
    ui->setupUi(this);
    setWindowTitle("UdpB:9999");

    udpSocket = new QUdpSocket(this);
    udpSocket->bind(9999);

    connect(udpSocket,&QUdpSocket::readyRead,this,&UdpB::dealMsg);
}

UdpB::~UdpB()
{
    delete ui;
}

void UdpB::dealMsg(){
    QHostAddress peerIp ;
    quint16 peerPort ;
    char buf[1024] = {0};
    qint64 length = udpSocket->readDatagram(buf,sizeof(buf),&peerIp,&peerPort);
    if(length > 0){
        QString msgTxt = QString("[%1:%2] %3")
                .arg(peerIp.toString())
                .arg(peerPort)
                .arg(buf);
        ui->msg->setText(msgTxt);
    }
}

void UdpB::on_pushButton_clicked()
{
    //获取对方的IP和端口
    QString ip = ui->ip->text();
    qint16 port = ui->port->text().toInt();
    QString msg = ui->msg->toPlainText();
    udpSocket->writeDatagram(msg.toUtf8().data(),QHostAddress(ip),port);
}