【MQTT】开发一个客户端，QT-Android安卓手机版本，Mosquitto替换成libhv库

云计算 2024年11月28日 15:35 1 admin

【MQTT】开发一个客户端，QT-Android安卓手机版本，使用libhv替换Mosquitto库

引言

本文将介绍如何在Qt框架下开发一个Android平台的MQTT客户端，使用libhv库替换传统的Mosquitto库。MQTT（Message Queuing Telemetry Transport）是一种轻量级的消息传输协议，广泛应用于物联网（IoT）领域。libhv是一个C/C++的跨平台网络库，支持多种协议，包括HTTP、WebSoCKet和MQTT等。

一、开发环境准备

1.1 安装Qt开发环境

下载并安装Qt框架：
```
https://www.qt.io/download
```
配置Android开发环境：
- 安装Android Studio并配置SDK和NDK。
- 在Qt Creator中配置Android工具链（SDK、NDK、JDK）。

1.2 下载并编译libhv库

克隆libhv仓库：

git clone https://github.com/ithewei/libhv.git
cd libhv

编译libhv库：
```
mkdir build && cd build
cmake ..
make
```

1.3 将libhv库集成到Qt项目中

在Qt项目的.pro文件中添加libhv库的路径：

INCLUDEPATH += /path/to/libhv/include
LIBS += -L/path/to/libhv/lib -lhv

二、编写MQTT客户端代码

2.1 创建Qt项目

打开Qt Creator，创建一个新的Qt Quick APPlication项目。
配置项目，选择Android工具链。

2.2 编写MQTT客户端逻辑

创建一个新的C++类 MQTTCLient，用于处理MQTT连接和消息处理。

在 MQTTClient.h中定义类：

#ifndef MQTTCLIENT_H
#define MQTTCLIENT_H

#include <QObject>
#include "hv/mqtt_client.h"

class MQTTClient : public QObject {
   Q_OBJECT
public:
   explicit MQTTClient(QObject *parent = nullptr);
   ~MQTTClient();

   void connectToBroker(const QString &host, int port, const QString &clientId);
   void subscribeTopic(const QString &topic);
   void publishMessage(const QString &topic, const QString &message);

private:
   mqtt_client_t *client;
};

#endif // MQTTCLIENT_H

在 MQTTClient.cpp中实现类：

#include "MQTTClient.h"
#include <QDebug>

MQTTClient::MQTTClient(QObject *parent) : QObject(parent) {
   client = mqtt_client_new();
}

MQTTClient::~MQTTClient() {
   mqtt_client_free(client);
}

void MQTTClient::connectToBroker(const QString &host, int port, const QString &clientId) {
   mqtt_client_config_t config;
   memset(&config, 0, sizeof(config));
   config.client_id = clientId.toStdString().c_str();
   config.host = host.toStdString().c_str();
   config.port = port;
   config.keepAlive = 60;

   config.on_connect = [](mqtt_client_t *cli) {
       qDebug() << "Connected to broker";
   };

   config.on_message = [](mqtt_client_t *cli, const mqtt_message_t *msg) {
       qDebug() << "Received message:" << QString::fromStdString(std::string((char*)msg->payload, msg->payloadlen));
   };

   mqtt_client_init(client, &config);
   mqtt_client_connect(client);
}

void MQTTClient::subscribeTopic(const QString &topic) {
   mqtt_client_subscribe(client, topic.toStdString().c_str(), 0);
}

void MQTTClient::publishMessage(const QString &topic, const QString &message) {
   mqtt_client_publish(client, topic.toStdString().c_str(), message.toStdString().c_str(), message.size(), 0, 0);
}

2.3 在Qt Quick UI中集成MQTT客户端

在主QML文件中添加按钮和文本输入，用于连接、订阅和发布消息。

在 mAIn.cpp中注册 MQTTClient类：

#include <QGuiapplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "MQTTClient.h"

int main(int argc, char *argv[]) {
   QGuiApplication app(argc, argv);

   QQmlApplicationEngine engine;

   MQTTClient mqttClient;
   engine.rootContext()->setContextProperty("mqttClient", &mqttClient);

   const QUrl url(QStringLiteral("qrc:/main.qml"));
   QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                    &app, [url](QObject *obj, const QUrl &objUrl) {
       if (!obj && url == objUrl)
           QCoreApplication::exit(-1);
   }, Qt::QueuedConnection);
   engine.load(url);

   return app.exec();
}

在QML文件中添加UI元素，并连接信号与槽：

import QtQuick 2.15
import QtQuick.Controls 2.15

ApplicationWindow {
   visible: true
   width: 640
   height: 480
   title: qsTr("MQTT Client")

   Column {
       anchors.centerIn: parent

       TextField {
           id: hostField
           placeholderText: "MQTT Broker Host"
       }

       TextField {
           id: portField
           placeholderText: "Port"
           inputMethodHints: Qt.ImhDigitsOnly
       }

       TextField {
           id: clientIdField
           placeholderText: "Client ID"
       }

       Button {
           text: "Connect"
           onClicked: mqttClient.connectToBroker(hostField.text, parseInt(portField.text), clientIdField.text)
       }

       TextField {
           id: topicField
           placeholderText: "Topic"
       }

       Button {
           text: "Subscribe"
           onClicked: mqttClient.subscribeTopic(topicField.text)
       }

       TextField {
           id: messageField
           placeholderText: "Message"
       }

       Button {
           text: "Publish"
           onClicked: mqttClient.publishMessage(topicField.text, messageField.text)
       }
   }
}