一、环境准备

操作系统：centos7.5

链接: https://pan.baidu.com/s/1BRYQ13RTIgkyD0GDsXB1jQ 提取码: 29e2
MQTT服务器

使用EMQX作为服务器

安装地址：https://www.emqx.io/zh/downloads?os=CentOS

安装方法

//1. 可能需要先执行
curl -s https://assets.emqx.com/scripts/install-emqx-rpm.sh | sudo bash

yum update -y
//2. 然后
yum install -y epel-release
//3. 安装
yum install -y openssl-devel openssl11 openssl11-devel

sudo yum install emqx -y

// 启动emqx
sudo systemctl start emqx

// 设置开机启动
sudo systemctl enable emqx

// 查看状态
sudo systemctl status emqx

默认账号密码：

账号：admin

密码：public

二、客户端开发

客户端操作系统为：UOS

QT版本：5.11.3

// 安装qt
sudo apt-get install qtbase5-dev

sudo apt-get install qtcreator

/// 安装MQTT的编译依赖
sudo apt-get install qtdeclarative5-dev

sudo apt-get install libqt5websockets5-dev

sudo apt-get instal qtbase5-private-dev

sudo apt install qttools5-private-dev

2.1 下载并且编译MQTT

下载

下载地址：GitHub - qt/qtmqtt at v5.11.3

注意下载的版本需要与QT版本一致。

编译

打开工程

修改头文件引用。

// 在qtmqtt-5.11.3/qtmqtt-5.11.3/src目录下执行
mkdir build
sudo /usr/lib/x86_64-linux-gnu/qt5/bin/qmake ..
make -j16

编译的内容会自动同步到/lib中。

下图头文件需要拷贝出来在客户端项目中需要使用。

2.2 客户端开发准备

新建qt项目

引用MQTT文件

添加头文件

/usr/include/c++/8

2.3 客户端开发源码

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "qmqttclient.h"
#include <QPushButton>
#include <QLineEdit>
#include <QWidget>
#include <QHBoxLayout>
class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

    QMqttClient*  pMqttClient_;
    QPushButton * pPushBtn_;
    QLineEdit * pLineEdit_;
    QWidget *pWdgMain_;
    QHBoxLayout *pLayoutMain_;
  void initUI();
  public slots:
        void btnClick();
        void brokerConnected();
       void updateLogStateChange();
       void brokerDisconnected();
       void receiveMess(const QByteArray &, const QMqttTopicName &);
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include <QDateTime>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    ,pMqttClient_(new QMqttClient(this))
    , pPushBtn_(new QPushButton())
    , pLineEdit_(new QLineEdit())
    , pWdgMain_(new QWidget())
    ,pLayoutMain_(new QHBoxLayout())
{
    pMqttClient_->setPort(1883);
    pMqttClient_->setHostname("10.4.17.80");
    pMqttClient_->connectToHost();
    connect(pMqttClient_, &QMqttClient::connected, this, &MainWindow::brokerConnected);
   connect(pMqttClient_, &QMqttClient::stateChanged, this, &MainWindow::updateLogStateChange);
   connect(pMqttClient_, &QMqttClient::disconnected, this, &MainWindow::brokerDisconnected);
   connect(pMqttClient_, &QMqttClient::pingResponseReceived, this, [this]() {
          const QString content = QDateTime::currentDateTime().toString()
                      + QLatin1String(" PingResponse")
                      + QLatin1Char('\n');
          qDebug() << content;
      });
    initUI();
}

MainWindow::~MainWindow()
{

}

void MainWindow::initUI()
{
    pLayoutMain_->addWidget(pLineEdit_);
    pLayoutMain_->addWidget(pPushBtn_);
    pWdgMain_->setLayout(pLayoutMain_);
    setCentralWidget(pWdgMain_);

    connect(pPushBtn_,&QPushButton::clicked,this,&MainWindow::btnClick);
}

void MainWindow::btnClick()
{
qInfo()<<"asdf:"<<pLineEdit_->text();
pMqttClient_->publish(QString("topic"),pLineEdit_->text().toLatin1());
}

void MainWindow::brokerConnected()
{
    qInfo() << "Connected!";
      if(pMqttClient_->state() == QMqttClient::Connected){
          pMqttClient_->subscribe(QString("topic"), 0);
          connect(pMqttClient_, SIGNAL(messageReceived(QByteArray,QMqttTopicName)), this, SLOT(receiveMess(QByteArray,QMqttTopicName)));
      }

}

void MainWindow::updateLogStateChange()
{
    const QString content = QDateTime::currentDateTime().toString()
                       + QLatin1String(": State Change")
                       + QString::number(pMqttClient_->state())
                       + QLatin1Char('\n');
       qInfo() << content;

}

void MainWindow::brokerDisconnected()
{
    qInfo() << "Disconnected!";
}

void MainWindow::receiveMess(const QByteArray &message, const QMqttTopicName &topic)
{
    QString content;
      content = QDateTime::currentDateTime().toString() + QLatin1Char('\n');
      content += QLatin1String(" Received Topic: ") + topic.name() + QLatin1Char('\n');
      content += QLatin1String(" Message: ") + message + QLatin1Char('\n');
      qInfo() << content;

}

#-------------------------------------------------
#
# Project created by QtCreator 2023-05-11T17:24:28
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = MQTTClient
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as 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 you use 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

CONFIG += c++11

SOURCES += \
        main.cpp \
        mainwindow.cpp

HEADERS += \
        mainwindow.h \
        include/QtMqtt/QtMqttDepends


unix:!macx: LIBS += -L$$PWD/../../../../../../../../usr/lib/ -lQt5Mqtt

INCLUDEPATH += /usr/include/c++/8
INCLUDEPATH += $$PWD/../../../../../../../../usr/include
DEPENDPATH += $$PWD/../../../../../../../../usr/include
INCLUDEPATH += $$PWD/include