Qt官方MQTT庫的使用，附一個MqttClient例子

修改説明：

修改時間：2019年5月31日

修改內容：mqtt庫編譯的説明

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開發環境：win7 64 + Qt5.9

記錄時間：2018年3月11日 00:48:42

聯系郵箱: [e-mail]（有問題發我郵件）

一：前言

　　最近在調試Mqtt通訊基礎上的加密，但因為Mqtt服務器是大家公用的，不能修改，所以就決定寫一個Mqtt的客戶端，與自己的開發板之間通信，使用客戶端模擬服務器的加密。因為自己在圖形編程中，自己對Qt比較熟悉，因此選擇了Qt進行編程。但后來發現Qt沒有集成Mqtt的組件，而使用網上大部分網友說說的emqtt作為Mqtt庫的話，雖然編譯沒有問題，但發現使用qmqtt雖然可以連接公司的Mqtt服務器，但不能通訊。后來上Y_o_u_T_u_b_e搜索了一下，看見有Qt官方介紹Mqtt的視頻，研究並寫了一個小Demo測試，發現可以使用，在文末會提供下載測試。在此，便簡單介紹一下，更多功能歡迎大家一起研究。

二：資料

介紹地址:https://codereview.qt-project.org/#/admin/projects/qt/qtmqtt
源碼下載：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：編譯生成QtMqtt的庫

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項目進行構建即可。  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。因此，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，重新編譯即可得到庫。

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3.1  git clone https://codereview.qt-project.org/qt/qtmqtt 下載源碼到本地

3.2 打開qtmqtt文件夾下的qtmqtt.pro工程

3.3 重新構建qtmqtt.pro

3.4 構建成功后，將輸出文件夾中的include和lib文件夾復制到其他地方

3.4 將lib文件夾下除了libQt5Mqtt.a、libQt5Mqttd.a、Qt5Mqtt.dll、Qt5Mqttd.dll四個文件之外的文件刪除

3.5 將include\QtMqtt 文件下除了qtmqttversion.h以外的.h文件，全部用qtmqtt\src\mqtt中同名的.h文件取代(include內的頭文件只是指向了

qtmqtt\src\mqtt中的頭文件)

四：新建自己的工程來使用QtMqtt的庫

4.1 新建一個Qt工程，基於Qidget，不使用系統生成UI

4.2將第三步獲得的lib和include文件夾復制到新工程的文件夾下。

4.3 修改.pro文件：

增加network模塊
QT += core gui network

增加頭文件搜索路徑
INCLUDEPATH += ./include

增加庫

4.4 根據 https://doc.qt.io/QtMQTT/qtmqtt-simpleclient-example.html 中的例子，簡單寫了一個先服務器發布消息的小Demo

 

五：代碼

//main.cpp
#include "QMqttClientTool.h"
#include <QApplication>

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

    return a.exec();
}

//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;//連接MQTT服務器
    QPushButton * btnPublish;//發布消息
    QLabel * qlbHostNameTag;
    QLabel * qlbHostPortTag;
    QLabel * qlbPubLishTopicTag;
    QLabel * qlbPublishMessageTag;
    QLineEdit * qleHostName;
    QLineEdit * qleHostPort;
    QLineEdit * qlePublishTopic;
    QLineEdit * qlePublishMessage;

private:
    QMqttClient * m_client;//mqtt client指針

private slots:
    void on_btnConnect_clicked(void);//連接MQTT服務器槽函數
    void on_btnPublish_clicked(void);//發布消息槽函數

};

#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()
{
    //未連接服務器則連接
    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 {//斷開連接
        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：代碼下載

點我下載QMqttClientTool