Qt5.8.0编译QtMqtt库并使用该库连接有人云的例子

一 编译QtMqtt库
Qt5.10才官方支持MQTT，但我用的Qt版本是5.8.0 Mingw_32BIT, 为了在Qt5.8.0上添加MQTT支持，需要自己编译源码

步骤：

(1) git clone https://github.com/qt/qtmqtt.git

(2) 使用Qt5.8.0自带的qtcreator打开qtmqtt的pro文件，然后切换到release模式编译

(3) 编译结束后会在工程生成的文件下生成如下一些文件

二 连接有人云
（1）首先按照有人云官方的教程添加一个透传设备，我添加的是“默认设备”（也可以是NBIOT等支持透传的设备），设备的ID为：00021153000000000001

（2）然后将这个设备使用有人虚拟串口软件映射为本地的虚拟串口，如下图所示

（3）创建Qt工程，主要代码如下：

#-------------------------------------------------
#
# Project created by QtCreator 2018-12-27T18:02:41
#
#-------------------------------------------------

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = MQTTest
TEMPLATE = app

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

LIBS += -LE:/EWorkSpace/20190109_mqtt/build-qtmqtt-Qt580_MINGW_32BIT-Release/bin -lQt5Mqtt

INCLUDEPATH += E:/EWorkSpace/20190109_mqtt/build-qtmqtt-Qt580_MINGW_32BIT-Release/include

SOURCES += main.cpp \
mainwidget.cpp \
mqttclient.cpp

HEADERS += \
mainwidget.h \
mqttclient.h

FORMS += \
mainwidget.ui
#ifndef MQTTCLIENT_H
#define MQTTCLIENT_H

#include <QObject>
#include <QtMqtt/QMqttClient>
#include <QtMqtt/QMqttSubscription>

typedef QMqttSubscription::SubscriptionState SubscriptionState;

class MQTTClient : public QObject
{
Q_OBJECT
public:
explicit MQTTClient(const QString &userName, const QString &passwordMD5, const QString &deviceId, QObject *parent = nullptr);
~MQTTClient();

bool isOpened();
void open();
void close();
void write(const QByteArray &data);

private:
QString m_userName;
QString m_passwordMD5;
QString m_deviceId;
QMqttClient *m_client;
QByteArray m_buffer;

private slots:
void doConnected();
void doDisconnected();
void doMessageReceived(const QByteArray &message, const QMqttTopicName &topic);
void doQMqttSubscriptionStateChanged(SubscriptionState subscriptionState);

signals:
void log(const QString &text);

public slots:
};

#endif // MQTTCLIENT_H
#include "mqttclient.h"
#include <QDebug>

#define MQTT_HOSTNAME "clouddata.usr.cn"
#define MQTT_PORT 1883

#define MQTT_CLIENT_SUBSCRIBE_PREFIX "$USR/DevTx"
#define MQTT_CLIENT_PUBLISH_PREFIX "$USR/DevRx"

MQTTClient::MQTTClient(const QString &userName, const QString &passwordMD5, const QString &deviceId, QObject *parent) : QObject(parent)
{
m_client=NULL;
this->m_userName=userName;
this->m_passwordMD5=passwordMD5;
this->m_deviceId=deviceId;
}

MQTTClient::~MQTTClient()
{
if(m_client!=NULL)
{
if(m_client->state()==QMqttClient::Connected)
{
m_client->disconnectFromHost();
}
delete m_client;
m_client=NULL;
}
}

bool MQTTClient::isOpened()
{
if(m_client==NULL)
{
return false;
}
else if(m_client->state()==QMqttClient::Connected)
{
return true;
}
else
{
return false;
}
}

void MQTTClient::open()
{
if(m_client!=NULL)
{
return;
}
m_client = new QMqttClient(this);
m_client->setHostname(MQTT_HOSTNAME);
m_client->setPort(MQTT_PORT);
m_client->setUsername(m_userName);
m_client->setClientId(QString("APP:%1").arg(m_userName));
m_client->setPassword(m_passwordMD5);
m_client->setProtocolVersion(QMqttClient::MQTT_3_1_1);

connect(m_client, SIGNAL(connected()), this, SLOT(doConnected()));
connect(m_client, SIGNAL(disconnected()), this, SLOT(doDisconnected()));
connect(m_client, SIGNAL(messageReceived(QByteArray,QMqttTopicName)), this, SLOT(doMessageReceived(QByteArray,QMqttTopicName)));

m_client->connectToHost();
emit log("MQTTClient 正在连接...");
}

void MQTTClient::close()
{
if(m_client!=NULL)
{
if(m_client->state()==QMqttClient::Connected)
{
m_client->disconnectFromHost();
}
delete m_client;
m_client=NULL;
}
}

void MQTTClient::write(const QByteArray &data)
{
if(m_client!=NULL)
{
m_client->publish(QString("%1/%2").arg(MQTT_CLIENT_PUBLISH_PREFIX).arg(this->m_deviceId), data);
emit log(QString("MQTTClient 正发布设备消息，设备ID: %1, 消息:%2").arg(this->m_deviceId).arg(QString::fromLatin1(data)));
}
}

void MQTTClient::doConnected()
{
emit log("MQTTClient 已建立连接！");
emit log(QString("MQTTClient 正订阅设备消息，设备ID: %1").arg(this->m_deviceId));
QMqttSubscription *subscription=m_client->subscribe(QString("%1/%2").arg(MQTT_CLIENT_SUBSCRIBE_PREFIX).arg(this->m_deviceId));
connect(subscription, SIGNAL(stateChanged(SubscriptionState)),
this, SLOT(doQMqttSubscriptionStateChanged(SubscriptionState)));
}

void MQTTClient::doDisconnected()
{
emit log("MQTTClient 已断开连接！");
this->close();
}

void MQTTClient::doMessageReceived(const QByteArray &message, const QMqttTopicName &topic)
{
emit log(QString("MQTTClient 接收到数据: %1").arg(QString::fromLatin1(message)));
}

void MQTTClient::doQMqttSubscriptionStateChanged(SubscriptionState subscriptionState)
{
if(subscriptionState==QMqttSubscription::Subscribed)
{
emit log("订阅设备消息成功！");
}
}
#ifndef MAINWIDGET_H
#define MAINWIDGET_H

#include <QWidget>
#include "mqttclient.h"

namespace Ui {
class MainWidget;
}

class MainWidget : public QWidget
{
Q_OBJECT

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

private slots:
void on_buttonConnect_clicked();

void on_buttonWrite_clicked();

void on_buttonClear_clicked();

void doLog(const QString &text);

private:
Ui::MainWidget *ui;

MQTTClient *m_mqttClient;
};

#endif // MAINWIDGET_H
#include "mainwidget.h"
#include "ui_mainwidget.h"

MainWidget::MainWidget(QWidget *parent) :
QWidget(parent),
ui(new Ui::MainWidget)
{
ui->setupUi(this);
m_mqttClient=NULL;
}

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

void MainWidget::on_buttonConnect_clicked()
{
if(m_mqttClient!=NULL)
{
m_mqttClient->close();
m_mqttClient=NULL;
}
m_mqttClient=new MQTTClient(ui->lineUsername->text(), ui->linePasswordMD5->text(), ui->lineDeviceId->text());
connect(m_mqttClient, SIGNAL(log(QString)), this, SLOT(doLog(QString)));
m_mqttClient->open();
}

void MainWidget::on_buttonWrite_clicked()
{
if((m_mqttClient==NULL) || (!m_mqttClient->isOpened()))
{
ui->textLog->append("MQTT客户端未打开!");
return;
}
m_mqttClient->write(ui->lineWrite->text().toLatin1());
}

void MainWidget::on_buttonClear_clicked()
{
ui->textLog->clear();
}

void MainWidget::doLog(const QString &text)
{
ui->textLog->append(text);
}
然后运行测试：

（------- 完 -------）
---------------------
作者：Keycer
来源：CSDN
原文：https://blog.csdn.net/zgrjkflmkyc/article/details/86159661
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