基于C++在windows下使用mosquitto实现MQTT发布客户端

1、MOSQUITTO简介

　　Mosquitto​是一个开源的 MQTT(Message Queuing Telemetry Transport)消息代理服务器，由 Eclipse Foundation 开发和维护。它采用 C/C++ 编写，以轻量级、高性能著称。Mosquitto 因其简单、稳定、轻量的特点，成为物联网领域最受欢迎的 MQTT 代理之一，特别适合中小型项目和资源受限环境。

2、MOSQUITTO环境部署

　　Mosquitto​在windows下支持安装版本x86\x64均支持，下载地址为：https://mosquitto.org/download/，下载安装完成后在编译器中配置所需的头文件环境及库环境(mosquitto.lib)，配置完成后即可进行Demo测试。

3、MOSQUITTO发布客户端搭建

　　初始化MQTT代码

#include <mosquitto.h>
#define MQTT_USER_NAME "admin"
#define MQTT_PASS_WORD "Admin12345"
#define MQTT_SERVER_IP_ADDRESS "10.50.2.88"
#define MQTT_SERVER_PORT 1883
#define PUBLISH_JSON_DATA_ORG "4321"
#define GR4_HWCS_MQTT_TOPIC "DATA_PUBLISH_DIRECT_ANDON/4321/GYYKQ/GR4_HWCS"
static struct mosquitto* mosq;
static bool mqtt_init_sign;
int init_mqtt(const std::string username, const std::string passwd, const std::string hostname, const int port)
{
    mosquitto_lib_init();

    mosq = mosquitto_new(nullptr, true, nullptr);//第一个形参指定为固定值后，派生类会出现发布数据失败的情况，因为不同的派生类共用一个client_id
    if (!mosq) {
        std::cerr << "Failed to create mosquitto instance!" << std::endl;
        return 0;
    }

    const char* usrname = username.c_str();
    const char* password = passwd.c_str();

    int rc = mosquitto_username_pw_set(mosq, usrname, password);
    if (rc != MOSQ_ERR_SUCCESS) {
        std::cerr << "Failed to set username/password: " << mosquitto_strerror(rc) << std::endl;
        mosquitto_destroy(mosq);
        mosquitto_lib_cleanup();
        return 0;
    }

    rc = mosquitto_connect(mosq, hostname.c_str(), port, 60);
    if (rc != MOSQ_ERR_SUCCESS) {
        std::cerr << "Connection failed: " << mosquitto_strerror(rc) << std::endl;

        std::cout << "Trying without authentication..." << std::endl;
        mosquitto_username_pw_set(mosq, nullptr, nullptr);

        rc = mosquitto_connect(mosq, hostname.c_str(), port, 60);
        if (rc != MOSQ_ERR_SUCCESS) {
            std::cerr << "Still failed: " << mosquitto_strerror(rc) << std::endl;
            mosquitto_destroy(mosq);
            mosquitto_lib_cleanup();
            return 0;
        }
    }

    //std::cout << "Connected to MQTT broker!" << std::endl;
    mosquitto_loop_start(mosq);
    mqtt_init_sign = true;
    return 1;
}

　　MQTT发布数据

int publish_data_to_server(const std::string topic, const std::string message)
{
    if (!mqtt_init_sign)
    {
        std::cout << "mqtt not init, can not send mqtt msg" << std::endl;
        return 0;
    }

    int rc = mosquitto_publish(mosq,
        nullptr,
        topic.c_str(),
        message.length(),
        message.c_str(),
        0,    // QoS 0
        false);

    if (rc == MOSQ_ERR_SUCCESS) {
        /*std::cout << "Message published successfully!" << std::endl;
        std::cout << "Topic: " << topic << std::endl;
        std::cout << "Message: " << message << std::endl;*/
        ;
    }
    else {
        std::cerr << "Publish failed: " << mosquitto_strerror(rc) << std::endl;
        return 0;
    }
    return 1;
}

　　测试用例

int main()
{
    init_mqtt(MQTT_USER_NAME, MQTT_PASS_WORD, MQTT_SERVER_IP_ADDRESS, MQTT_SERVER_PORT);
    publish_data_to_server(GR4_HWCS_MQTT_TOPIC,"test message");
}