一直想写博客但是太懒了。。。根据最近做项目用到的东西就写个UDP吧，希望对大家有所帮助，嗯，其他的以后想起来再写。

主要内容：qt作为客户端实现报文的收发，用定时器实现定时写（心跳包），可断开重新连接。

测试别忘记关掉防火墙。

以下代码是简化过的，仅供参考，如有不当之处，欢迎指正。

下载链接（永久有效，失效请评论）：

链接：https://pan.baidu.com/s/1aFmmJdO6s5QcRcSyIZysYA 
提取码：a3nk

clent界面：

 UdpClient.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    udpclient.cpp

HEADERS += \
    udpclient.h

FORMS += \
    udpclient.ui

QT += network

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

udpclient.h

#ifndef UDPCLIENT_H
#define UDPCLIENT_H

#include <QMainWindow>
#include <QUdpSocket>

QT_BEGIN_NAMESPACE
namespace Ui {
    class UdpClient;
}
QT_END_NAMESPACE

class UdpClient : public QMainWindow {
    Q_OBJECT

public:
    UdpClient(QWidget *parent = nullptr);
    ~UdpClient();

private slots:
    void on_connet_pushButton_clicked();
    void sendData();
    void readData();

    void on_connect_pushButton_clicked();

private:
    Ui::UdpClient *ui;
    QUdpSocket *udpClient;
    QString ip;
    qint64 port;
    qint64 reciveTime;
    qint64 sendTime;
    QTimer *writeTimer;

    static const quint64 RESPONSE_INTERVAL;//write周期
    static const quint64 HEARTBEAT_TIMEOUT;//超时未应答时间

    bool isVaildIp(QString &ip);
    void resetStatues();

    bool btnStatues;
};
#endif // UDPCLIENT_H

 udpclient.cpp

#include "udpclient.h"
#include "ui_udpclient.h"
#include <QTimer>
#include <QMessageBox>

const quint64 UdpClient::RESPONSE_INTERVAL = 5; //s
const quint64 UdpClient::HEARTBEAT_TIMEOUT = 15; //s

UdpClient::UdpClient(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::UdpClient) {
    ui->setupUi(this);
    writeTimer = nullptr;
    ip = "192.168.56.200";
    port = 8888;
    sendTime = 0;
    reciveTime = 0;
    btnStatues = false;
    udpClient = new QUdpSocket(this);
    udpClient->bind(QHostAddress(ip), QUdpSocket::ShareAddress);
    QObject::connect(udpClient, SIGNAL(readyRead()), this, SLOT(readData()));
    writeTimer = new QTimer;
    QObject::connect(writeTimer, SIGNAL(timeout()), this, SLOT(sendData()));
}

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

bool UdpClient::isVaildIp(QString &ip) {
    QHostAddress test;
    if (!test.setAddress(ip)) {
        return false;
    }
    return true;
}

void UdpClient::sendData() {
    quint64 now = time(NULL);
    if ((now - sendTime) > RESPONSE_INTERVAL) {
        udpClient->writeDatagram("{\"order\":\"HELLO\"}", QHostAddress(ip), port);
        ui->send_lable->setText("HELLO");
#ifdef QT_DEBUG
        qDebug() << "send: HELLO";
#endif
        sendTime = now;
    }
}

void UdpClient::readData() {
    QByteArray arr;
    quint64 now = time(NULL);
    while(udpClient->hasPendingDatagrams()) {
        arr.resize(udpClient->bytesAvailable());
        udpClient->readDatagram(arr.data(), arr.size());
        reciveTime = now;
#ifdef QT_DEBUG
        qDebug() << "read: " << arr.data();
#endif
    }
    if (!strcmp(arr.data(), "HELLO")) {
        ui->connect_pushButton->setText("断开");
        btnStatues = true;
        ui->recive_lable->setText(arr.data());
    }  else {
        if(now - reciveTime > HEARTBEAT_TIMEOUT) {
            ui->connect_pushButton->setText("连接");
            btnStatues = false;
        }
    }
}

void UdpClient::resetStatues() {
    sendTime = 0;
    reciveTime = 0;
}

void UdpClient::on_connect_pushButton_clicked() {
    if(!btnStatues) { //未连接
        if(!isVaildIp(ip)) {
            QMessageBox::warning(NULL, "提示", "IP地址不合法！", QMessageBox::Ok);
            return;
        }
    } else {
        udpClient->close();//必须关闭，不然无法重新绑定
        resetStatues();
        btnStatues = false;
        writeTimer->stop();
        ui->connect_pushButton->setText("连接");
        return;
    }
#ifdef QT_DEBUG
    qDebug() << "connecting: " << ip << " port: " << port;
#endif
    udpClient->bind(QHostAddress(ip), QUdpSocket::ShareAddress);
    writeTimer->start(0);
}