【Qt官方MQTT库的使用，附一个MqttClient例子】

Qt官方MQTT库的使用，附一个MqttClient例子

修改説明：

修改時間：2019年5月31日

修改内容：mqtt庫編譯的説明

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开发环境：win7 64 + Qt5.9

记录时间：2018年3月11日 00:48:42

联系邮箱: yexiaopeng1992@126.com（有问题发我邮件）

一：前言

　　最近在调试Mqtt通信基础上的加密，但由于Mqtt服务器是你们公用的，不能修改，因此就决定写一个Mqtt的客户端，与本身的开发板之间通讯，使用客户端模拟服务器的加密。由于本身在图形编程中，本身对Qt比较熟悉，所以选择了Qt进行编程。但后来发现Qt没有集成Mqtt的组件，而使用网上大部分网友说说的emqtt做为Mqtt库的话，虽然编译没有问题，但发现使用qmqtt虽然能够链接公司的Mqtt服务器，但不能通信。后来上Y_o_u_T_u_b_e搜索了一下，看见有Qt官方介绍Mqtt的视频，研究并写了一个小Demo测试，发现可使用，在文末会提供下载测试。在此，便简单介绍一下，更多功能欢迎你们一块儿研究。

二：资料

介绍地址:https://codereview.qt-project.org/#/admin/projects/qt/qtmqtt
源码下载：git clone https://codereview.qt-project.org/qt/qtmqtt
Qt MQTT Examples：https://doc.qt.io/QtMQTT/qtmqtt-examples.html
Qt MQTT Client Example：https://doc.qt.io/QtMQTT/qtmqtt-simpleclient-example.html

三：编译生成QtMqtt的库

修改説明

當前Qt已經將MQTT的代碼上傳至github，在使用這個版本進行庫生成時，有些許差異。特此説明

github地址：https://github.com/qt/qtmqtt 

下載后，打開最外層的 qtmqtt.pro項目進行構建便可。  構建中會報文件找不到的錯誤。如  <QtMqtt/qmqttglobal.h>等文件，

按照這種寫法，文件應該在Qt按照路徑下，但文件是存在 項目的 src\mqtt 路徑下。所以，在Qt安裝路徑的頭文件目錄下，新建QtMqtt目錄，將對應文件放入，从新編譯便可获得庫。

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3.1  git clone https://codereview.qt-project.org/qt/qtmqtt 下载源码到本地

3.2 打开qtmqtt文件夹下的qtmqtt.pro工程

3.3 从新构建qtmqtt.pro

3.4 构建成功后，将输出文件夹中的include和lib文件夹复制到其余地方

3.4 将lib文件夹下除了libQt5Mqtt.a、libQt5Mqttd.a、Qt5Mqtt.dll、Qt5Mqttd.dll四个文件以外的文件删除

3.5 将include\QtMqtt 文件下除了qtmqttversion.h之外的.h文件，所有用qtmqtt\src\mqtt中同名的.h文件取代(include内的头文件只是指向了

qtmqtt\src\mqtt中的头文件)

四：新建本身的工程来使用QtMqtt的库

4.1 新建一个Qt工程，基于Qidget，不使用系统生成UI

4.2将第三步得到的lib和include文件夹复制到新工程的文件夹下。

4.3 修改.pro文件：

增长network模块
QT += core gui network

增长头文件搜索路径
INCLUDEPATH += ./include

增长库

4.4 根据 https://doc.qt.io/QtMQTT/qtmqtt-simpleclient-example.html 中的例子，简单写了一个先服务器发布消息的小Demo

 

五：代码

 1 //main.cpp
 2 #include "QMqttClientTool.h"
 3 #include <QApplication>
 4 
 5 int main(int argc, char *argv[])  6 {  7  QApplication a(argc, argv);  8  QMqttClientTool w;  9  w.show(); 10 
11     return a.exec(); 12 }

//QMqttClientTool.h
#ifndef QMQTTCLIENTTOOL_H #define QMQTTCLIENTTOOL_H #include <QWidget> #include "QtMqtt/QMqttClient" #include "QPushButton" #include "QLineEdit" #include "QLabel"

class QMqttClientTool : public QWidget { Q_OBJECT public: QMqttClientTool(QWidget *parent = 0); ~QMqttClientTool(); QPushButton * btnConnect;//链接MQTT服务器
    QPushButton * btnPublish;//发布消息
    QLabel * qlbHostNameTag; QLabel * qlbHostPortTag; QLabel * qlbPubLishTopicTag; QLabel * qlbPublishMessageTag; QLineEdit * qleHostName; QLineEdit * qleHostPort; QLineEdit * qlePublishTopic; QLineEdit * qlePublishMessage; private: QMqttClient * m_client;//mqtt client指针

private slots: void on_btnConnect_clicked(void);//链接MQTT服务器槽函数
    void on_btnPublish_clicked(void);//发布消息槽函数
 }; #endif // QMQTTCLIENTTOOL_H

//QMqttClientTool.cpp
#include "QMqttClientTool.h" #include "QDebug" #include <QtWidgets/QMessageBox> QMqttClientTool::QMqttClientTool(QWidget *parent) : QWidget(parent) { this->setMaximumSize(600,200); this->setMinimumSize(600,200); m_client =  new QMqttClient(this); btnConnect =  new QPushButton(this); btnPublish =  new QPushButton(this); qlbHostNameTag =  new QLabel(this); qlbHostPortTag =  new QLabel(this); qlbPubLishTopicTag =  new QLabel(this); qlbPublishMessageTag =  new QLabel(this); qleHostName =  new QLineEdit(this); qleHostPort =  new QLineEdit(this); qlePublishTopic =  new QLineEdit(this); qlePublishMessage =  new QLineEdit(this); QFont ft; ft.setPointSize(15); ft.setBold(1); qlbHostNameTag->move(6,6); qlbHostNameTag->setText("Host"); qlbHostNameTag->setFont(ft); qlbHostNameTag->setMaximumSize(65,35); qlbHostNameTag->setMinimumSize(65,35); qleHostName->move(60,6); qleHostName->setFont(ft); qleHostName->setMaximumSize(200,35); qleHostName->setMinimumSize(200,35); qlbHostPortTag->move(270,6); qlbHostPortTag->setText("Port"); qlbHostPortTag->setFont(ft); qlbHostPortTag->setMaximumSize(65,35); qlbHostPortTag->setMinimumSize(65,35); qleHostPort->move(324,6); qleHostPort->setFont(ft); qleHostPort->setMaximumSize(60,35); qleHostPort->setMinimumSize(60,35); btnConnect->move(390,6); btnConnect->setText("Connect"); btnConnect->setFont(ft); btnConnect->setMaximumSize(120,35); btnConnect->setMinimumSize(120,35); qlbPubLishTopicTag->move(6,50); qlbPubLishTopicTag->setText("PublishTopic"); qlbPubLishTopicTag->setFont(ft); qlbPubLishTopicTag->setMaximumSize(130,35); qlbPubLishTopicTag->setMinimumSize(130,35); qlePublishTopic->move(145,50); qlePublishTopic->setFont(ft); qlePublishTopic->setMaximumSize(240,35); qlePublishTopic->setMinimumSize(240,35); btnPublish->move(390,50); btnPublish->setText("Publish"); btnPublish->setFont(ft); btnPublish->setMaximumSize(120,35); btnPublish->setMinimumSize(120,35); qlbPublishMessageTag->move(6,94); qlbPublishMessageTag->setText("PublishMessage"); qlbPublishMessageTag->setFont(ft); qlbPublishMessageTag->setMaximumSize(160,35); qlbPublishMessageTag->setMinimumSize(160,35); qlePublishMessage->move(170,94); qlePublishMessage->setFont(ft); qlePublishMessage->setMaximumSize(400,35); qlePublishMessage->setMinimumSize(400,35); connect(btnConnect,SIGNAL(clicked()),this,SLOT(on_btnConnect_clicked())); connect(btnPublish,SIGNAL(clicked()),this,SLOT(on_btnPublish_clicked())); } QMqttClientTool::~QMqttClientTool() { } void QMqttClientTool::on_btnConnect_clicked() { //未链接服务器则链接
    if (m_client->state() == QMqttClient::Disconnected) { btnConnect->setText(tr("Disconnect")); m_client->setHostname(qleHostName->text()); m_client->setPort(qleHostPort->text().toInt()); qleHostName->setEnabled(false); qleHostPort->setEnabled(false); m_client->connectToHost(); } else {//断开链接
        btnConnect->setText(tr("Connect")); qleHostName->setEnabled(true); qleHostPort->setEnabled(true); m_client->disconnectFromHost(); } } void QMqttClientTool::on_btnPublish_clicked() { if (m_client->publish(qlePublishTopic->text(),qlePublishMessage->text().toUtf8()) == -1) QMessageBox::critical(this, QLatin1String("Error"), QLatin1String("Could not publish message")); }

//QMqttClientTool.pro
#------------------------------------------------- # # Project created by QtCreator 2018-03-10T16:12:38 # #------------------------------------------------- QT += core gui network greaterThan(QT_MAJOR_VERSION, 4): QT += widgets TARGET = QMqttClientTool 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 SOURCES += \ main.cpp \ QMqttClientTool.cpp HEADERS += \ QMqttClientTool.h INCLUDEPATH += ./include win32:CONFIG(release, debug|release): LIBS += -L$$PWD/lib/ -lQt5Mqtt else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/lib/ -lQt5Mqttd INCLUDEPATH += $$PWD/include DEPENDPATH += $$PWD/include win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$PWD/lib/libQt5Mqtt.a else:win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$PWD/lib/libQt5Mqttd.a else:win32:!win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$PWD/lib/Qt5Mqtt.lib else:win32:!win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$PWD/lib/Qt5Mqttd.lib

六：代码下载

点我下载QMqttClientTool