#-------------------------------------------------
#
# Project created by QtCreator 2018-12-09T16:01:34
#
#-------------------------------------------------

QT       += core gui network

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = udpclient
TEMPLATE = app


SOURCES += main.cpp\
        udpclient.cpp

HEADERS  += udpclient.h

FORMS    += udpclient.ui

服务器端

#include "udpserver.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    UdpServer w;
    w.show();

    return a.exec();
}

#ifndef UDPSERVER_H
#define UDPSERVER_H

#include <QtWidgets>
#include <QUdpSocket>

namespace Ui {
class UdpServer;
}

class UdpServer : public QWidget
{
    Q_OBJECT

public:
    explicit UdpServer(QWidget *parent = 0);
    ~UdpServer();

private slots:
    void readPendingDatagrams();

    void on_sendBtn_clicked();

private:
    Ui::UdpServer *ui;
    QUdpSocket *udpServer;
    QHostAddress sender;
    quint16 senderPort;
};

#endif // UDPSERVER_H

#include "udpserver.h"
#include "ui_udpserver.h"

UdpServer::UdpServer(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::UdpServer)
{
    ui->setupUi(this);

    udpServer = new QUdpSocket(this);
    udpServer->bind(QHostAddress::LocalHost, 7755);  //127.0.0.1

    connect(udpServer, SIGNAL(readyRead()),
            this, SLOT(readPendingDatagrams()));
}

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


void UdpServer::readPendingDatagrams()
{
    while (udpServer->hasPendingDatagrams()) {  //如果缓冲区有至少一个数据包，那么返回真
        QByteArray datagram;
        datagram.resize(udpServer->pendingDatagramSize());  //重设接收缓冲区大小为待读取的字节数

        udpServer->readDatagram(datagram.data(), datagram.size(),
                                &sender, &senderPort);

        //业务逻辑
        ui->recvEdit->setText(QString(datagram));
    }
}

void UdpServer::on_sendBtn_clicked()
{
    //给客户端发送一定要等待接收到客户端地址以后
    udpServer->writeDatagram(ui->sendEdit->text().toUtf8(), sender, senderPort);
}

客户端

#include "udpclient.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    UdpClient w;
    w.show();

    return a.exec();
}

#ifndef UDPCLIENT_H
#define UDPCLIENT_H

#include <QtWidgets>
#include <QUdpSocket>

namespace Ui {
class UdpClient;
}

class UdpClient : public QWidget
{
    Q_OBJECT

public:
    explicit UdpClient(QWidget *parent = 0);
    ~UdpClient();

private slots:
    void on_sendBtn_clicked();
    void readPendingDatagrams();

private:
    Ui::UdpClient *ui;
    QUdpSocket *cliSocket;
};

#endif // UDPCLIENT_H

#include "udpclient.h"
#include "ui_udpclient.h"

UdpClient::UdpClient(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::UdpClient)
{
    ui->setupUi(this);

    cliSocket = new QUdpSocket(this);

    connect(cliSocket, SIGNAL(readyRead()),
            this, SLOT(readPendingDatagrams()));
}

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

void UdpClient::on_sendBtn_clicked()
{
    cliSocket->writeDatagram(ui->sendEdit->text().toUtf8(), QHostAddress::LocalHost, 7755);
}

void UdpClient::readPendingDatagrams()
{
    while (cliSocket->hasPendingDatagrams()) {  //如果缓冲区有至少一个数据包，那么返回真
        QByteArray datagram;
        datagram.resize(cliSocket->pendingDatagramSize());  //重设接收缓冲区大小为待读取的字节数

        cliSocket->readDatagram(datagram.data(), datagram.size(),
                                NULL, NULL);

        //业务逻辑
        ui->recvEdit->setText(QString(datagram));
    }
}