Liunx下用C++实现MQTT的接收与发送

继续上次《Liunx下用C语言实现MQTT的接收与发送（上）（下）》，本人探寻了如何基于paho.mqtt.c库开发C++版本的MQTT。事实上，paho官网有paho.mqtt.c++库，不过笔者进去后玩不怎么转，可能是笔者不太灵光。

---

环境准备

笔者忽然想到，在《Liunx下用C语言实现MQTT的接收与发送（上）》中，好像安装了些mqtt的动态库，他们是啥情况呢？

本人推断是封装了，在src里面，被我之前排除的库文件。简单测试调用了一下，还真是。

因此，本人又开始封装了。（这里的脑回路太漫长了，几句话也说不清楚，这MQTT任务倒腾了我三天半终于结束了）。

---

封装mqtt的C++版本库

mqtt.h:

#ifndef MQTT_H
#define MQTT_H

#include 
#include 

using namespace std;

class MQTT {
public:
    bool useSSL;
    //实例 ID，购买后从控制台获取
    string instanceId;
    //接入点域名，从控制台获取
    string host;
    //客户端使用的 GroupID，从控制台申请
    string groupId;
    //客户端 ClientID 的后缀，由业务自行指定，只需要保证全局唯一即可
    string deviceId;
    //账号 AccessKey，从账号控制台获取
    string accessKey;
    //账号 SecretKey，从账号控制台获取
    string secretKey;
    //使用的协议端口，默认 tcp 协议使用1883，如果需要使用 SSL 加密，端口设置成8883，具体协议和端口参考文档链接https://help.aliyun.com/document_detail/44867.html?spm=a2c4g.11186623.6.547.38d81cf7XRnP0C
    int port = 1883;
    //测试收发消息的 Topic
    string topic;

    int (*messageArrived)(void *context, char *topicName, int topicLen, MQTTAsync_message *m);
    void (*onConnectFailure)(void *context, MQTTAsync_failureData *response);
    void (*onSubcribe)(void *context, MQTTAsync_successData *response);
    void (*onConnectServer)(void *context, MQTTAsync_successData *response);
    void (*onConnectClient)(void *context, MQTTAsync_successData *response);
    void (*onDisconnect)(void *context, MQTTAsync_successData *response);
    void (*onPublishFailure)(void *context, MQTTAsync_failureData *response);
    void (*onPublish)(void *context, MQTTAsync_successData *response);
    void (*connectionLost)(void *context, char *cause);

    MQTT();

    void init(void);
    int subscript_connect(void);
    int subscript_disconnect(void);
    int publish_connect(void);
    int publish_send(char *msg);
    int publish_disconnect(void);

    MQTTAsync client;
    char clientIdUrl[64];
    char passWord[100];
    char userName[128];

    int connected;
};

#endif

mqtt.cpp:

#include 
#include 
#include 

#if defined(WIN32)
#define sleep Sleep
#else

#include 
#include 
#include 

#endif

#include "mqtt.h"

MQTT::MQTT()
{
    instanceId = "mqtt-cn-oew1w1cq50a";
    host = "localhost";// ip地址
    groupId = "GID_DEVICE";
    deviceId = "fs1704";
    accessKey = "LTAI4G6gf4KQpMTmMEsaf6oF";
    secretKey = "pwAzZb7DFMjju3TYI5lmcShw2nlZUs";
    topic = "MQTT/test";
    port = 1883;
    connected = 0;
    useSSL = false;
}

void MQTT::init(void)
{
    char tempData[100];
    int len = 0;
    printf("mqtt:init:topic:%s:deviceId:%s\n", topic.c_str(), deviceId.c_str());
    //ClientID要求使用 GroupId 和 DeviceId 拼接而成，长度不得超过64个字符
    snprintf(clientIdUrl, 64, "%s@@@%s", groupId.c_str(), deviceId.c_str());
    //username和 Password 签名模式下的设置方法，参考文档 https://help.aliyun.com/document_detail/48271.html?spm=a2c4g.11186623.6.553.217831c3BSFry7
    HMAC(EVP_sha1(), (unsigned char *)secretKey.c_str(), strlen(secretKey.c_str()), (const unsigned char *)clientIdUrl, strlen(clientIdUrl), (unsigned char *)tempData, (unsigned int *)&len);
    int passWordLen = EVP_EncodeBlock((unsigned char *) passWord, (const unsigned char *)tempData, len);
    passWord[passWordLen] = '\0';
    printf("passWord is %s\n", passWord);
    snprintf(userName, 128, "Signature|%s|%s", accessKey.c_str(), instanceId.c_str());
}

int MQTT::subscript_connect(void)
{
    int cleanSession = 1;
    int rc = 0;
    //1.create client
    MQTTAsync_createOptions create_opts = MQTTAsync_createOptions_initializer;
    create_opts.sendWhileDisconnected = 0;
    create_opts.maxBufferedMessages = 10;
    char url[100];
    if (useSSL) {
        snprintf(url, 100, "ssl://%s:%d", host.c_str(), port);
    } else {
        snprintf(url, 100, "tcp://%s:%d", host.c_str(), port);
    }
    rc = MQTTAsync_createWithOptions(&client, url, clientIdUrl, MQTTCLIENT_PERSISTENCE_NONE, NULL, &create_opts);
    rc = MQTTAsync_setCallbacks(client, client, connectionLost, messageArrived, NULL);
    //2.connect to server
    MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
    conn_opts.MQTTVersion = MQTTVERSION_3_1_1;
    conn_opts.keepAliveInterval = 60;
    conn_opts.cleansession = cleanSession;
    conn_opts.username = userName;
    conn_opts.password = passWord;
    conn_opts.onSuccess = onConnectServer;
    conn_opts.onFailure = onConnectFailure;
    conn_opts.context = client;
    //如果需要使用 SSL 加密
    if (useSSL) {
        MQTTAsync_SSLOptions ssl =MQTTAsync_SSLOptions_initializer;
        conn_opts.ssl = &ssl;
    } else {
        conn_opts.ssl = NULL;
    }
    conn_opts.automaticReconnect = 1;
    conn_opts.connectTimeout = 3;
    if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS) {
        printf("Failed to start connect, return code %d\n", rc);
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}

int MQTT::subscript_disconnect(void)
{
    int rc = 0;
    MQTTAsync_disconnectOptions disc_opts = MQTTAsync_disconnectOptions_initializer;
    disc_opts.onSuccess = onDisconnect;
    if ((rc = MQTTAsync_disconnect(client, &disc_opts)) != MQTTASYNC_SUCCESS) {
        printf("Failed to start disconnect, return code %d\n", rc);
        return EXIT_FAILURE;
    }
    while (connected)
        sleep(1);
    MQTTAsync_destroy(&client);
    return EXIT_SUCCESS;
}

int MQTT::publish_connect(void)
{
    int cleanSession = 1;
    int rc = 0;
    //1.create client
    MQTTAsync_createOptions create_opts = MQTTAsync_createOptions_initializer;
    create_opts.sendWhileDisconnected = 0;
    create_opts.maxBufferedMessages = 10;
    char url[100];
    if (useSSL) {
        snprintf(url, 100, "ssl://%s:%d", host.c_str(), port);
    } else {
        snprintf(url, 100, "tcp://%s:%d", host.c_str(), port);
    }
    rc = MQTTAsync_createWithOptions(&client, url, clientIdUrl, MQTTCLIENT_PERSISTENCE_NONE, NULL, &create_opts);
    rc = MQTTAsync_setCallbacks(client, client, connectionLost, messageArrived, NULL);
    //2.connect to server
    MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
    conn_opts.MQTTVersion = MQTTVERSION_3_1_1;
    conn_opts.keepAliveInterval = 60;
    conn_opts.cleansession = cleanSession;
    conn_opts.username = userName;
    conn_opts.password = passWord;
    conn_opts.onSuccess = onConnectClient;
    conn_opts.onFailure = onConnectFailure;
    conn_opts.context = client;
    //如果需要使用 SSL 加密
    if (useSSL) {
        MQTTAsync_SSLOptions ssl =MQTTAsync_SSLOptions_initializer;
        conn_opts.ssl = &ssl;
    } else {
        conn_opts.ssl = NULL;
    }
    conn_opts.automaticReconnect = 1;
    conn_opts.connectTimeout = 3;
    if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS) {
        printf("Failed to start connect, return code %d\n", rc);
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}

int MQTT::publish_send(char *msg)
{
    int rc = 0;

    //3.publish msg
    MQTTAsync_responseOptions pub_opts = MQTTAsync_responseOptions_initializer;
    pub_opts.onSuccess = onPublish;
    pub_opts.onFailure = onPublishFailure;
    rc = MQTTAsync_send(client, topic.c_str(), strlen(msg), msg, 0, 0, &pub_opts);
    if(rc != MQTTASYNC_SUCCESS) {
        printf("mqtt:publish:failed:%s\n", msg);
        return EXIT_FAILURE;
    } else {
        printf("mqtt:publish:success:%s\n", msg);
        return EXIT_SUCCESS;
    }
}

int MQTT::publish_disconnect(void)
{
    int rc = 0;
    MQTTAsync_disconnectOptions disc_opts = MQTTAsync_disconnectOptions_initializer;
    disc_opts.onSuccess = onDisconnect;
    if ((rc = MQTTAsync_disconnect(client, &disc_opts)) != MQTTASYNC_SUCCESS) {
        printf("Failed to start disconnect, return code %d\n", rc);
        return EXIT_FAILURE;
    }
    while (connected)
        sleep(1);
    MQTTAsync_destroy(&client);
    return EXIT_SUCCESS;
}

可以看到，代码中出现了#include ，这个库在哪里呢？

其实它就在动态库里/usr/local/lib下面的，具体是哪个我忘了，没记录。

为了方便管理，我也把这两个文件放到mqtt文件夹里。

---

MQTT数据订阅端

#include 
#include 
#include 
#include 

#include "mqtt.h"

MQTT mqttServer;

using namespace std;

int messageArrivedServer(void *context, char *topicName, int topicLen, MQTTAsync_message *m)
{
    printf("recv message from %s ,body is %s\n", topicName, (char *) m->payload);
    
    // TODO::在此处增加接收内容解析程序


    MQTTAsync_freeMessage(&m);
    MQTTAsync_free(topicName);
    return 1;
}

void onConnectFailureServer(void *context, MQTTAsync_failureData *response)
{
    if(mqttServer.connected)
        mqttServer.connected = 0;

    printf("mqtt:connect failed, rc %d\n", response ? response->code : -1);
    MQTTAsync client = (MQTTAsync) context;
}

void onSubcribeServer(void *context, MQTTAsync_successData *response)
{
    printf("subscribe success\n");
}

void onConnectServer(void *context, MQTTAsync_successData *response)
{
    if(!mqttServer.connected)
        mqttServer.connected = 1;

    //连接成功的回调，只会在第一次 connect 成功后调用，后续自动重连成功时并不会调用，因此应用需要自行保证每次 connect 成功后重新订阅
    printf("mqtt:server:connect success\n");
    MQTTAsync client = (MQTTAsync) context;
    //do sub when connect success
    MQTTAsync_responseOptions sub_opts = MQTTAsync_responseOptions_initializer;
    sub_opts.onSuccess = mqttServer.onSubcribe;
    int rc = 0;
    if ((rc = MQTTAsync_subscribe(client, mqttServer.topic.c_str(), 1, &sub_opts)) != MQTTASYNC_SUCCESS) {
        printf("Failed to subscribe, return code %d\n", rc);
    }
}

void onDisconnectServer(void *context, MQTTAsync_successData *response)
{
    if(mqttServer.connected)
        mqttServer.connected = 0;

    printf("mqtt:connect disconnect\n");
}

void onPublishFailureServer(void *context, MQTTAsync_failureData *response)
{
    printf("Publish failed, rc %d\n", response ? -1 : response->code);
}

void connectionLostServer(void *context, char *cause)
{
    if(mqttServer.connected)
        mqttServer.connected = 0;

    printf("mqtt:server:connection lost\n");
}

int main()
{
    mqttServer.topic = "MQTT/#";
    mqttServer.deviceId = "fs1704";//mac地址;  id不能相同
    mqttServer.messageArrived = messageArrivedServer;
    mqttServer.onConnectFailure = onConnectFailureServer;
    mqttServer.onSubcribe = onSubcribeServer;
    mqttServer.onConnectServer = onConnectServer;
    mqttServer.onDisconnect = onDisconnectServer;
    mqttServer.onPublishFailure = onPublishFailureServer;
    mqttServer.connectionLost = connectionLostServer;

    mqttServer.init();

    while(true) {
        if(mqttServer.subscript_connect()) {
            sleep(1);
            continue;
        }
        break;
    }
    while(true) {
        sleep(2);
    }
    mqttServer.subscript_disconnect();
    return 0;
}

可以看到，接收内容处理是在int messageArrivedServer(void *context, char *topicName, int topicLen, MQTTAsync_message *m)函数的，我也在此处打了TODO。

订阅话题是在void onConnectServer(void *context, MQTTAsync_successData *response)函数完成。

---

MQTT数据发布端

#include 
#include 
#include 
#include 

#include "mqtt.h"

MQTT mqttClient;

using namespace std;

void onConnectFailureClient(void *context, MQTTAsync_failureData *response)
{
    mqttClient.connected = 0;
    printf("mqtt:connect failed, rc %d\n", response ? response->code : -1);
    MQTTAsync client = (MQTTAsync) context;
}

void onConnectClient(void *context, MQTTAsync_successData *response)
{
    mqttClient.connected = 1;
    //连接成功的回调，只会在第一次 connect 成功后调用，后续自动重连成功时并不会调用，因此应用需要自行保证每次 connect 成功后重新订阅
    printf("mqtt:client:connect success\n");
}

void onDisconnectClient(void *context, MQTTAsync_successData *response)
{
    mqttClient.connected = 0;
    printf("mqtt:connect disconnect\n");
}

void onPublishFailureClient(void *context, MQTTAsync_failureData *response)
{
    printf("Publish failed, rc %d\n", response ? -1 : response->code);
}

void onPublishClient(void *context, MQTTAsync_successData *response)
{
    printf("mqtt:publish:send success\n");
}

void connectionLostClient(void *context, char *cause)
{
    mqttClient.connected = 0;
    printf("mqtt:client:connection lost\n");
}

int main()
{
    char msg[1024];

    mqttClient.topic = "MQTT/test";
    mqttClient.deviceId = "fs0504";//mac地址; id不能相同
    mqttClient.onConnectFailure = onConnectFailureClient;
    mqttClient.onConnectClient = onConnectClient;
    mqttClient.onDisconnect = onDisconnectClient;
    mqttClient.onPublishFailure = onPublishFailureClient;
    mqttClient.onPublish = onPublishClient;
    mqttClient.connectionLost = connectionLostClient;

    mqttClient.init();

    while(true) {
        if(mqttClient.publish_connect()) {
            sleep(1);
            continue;
        }

        while(true) {
            sprintf(msg, "hello!! this is mqtt demo\n");

            mqttClient.publish_send(msg);

            sleep(1);

        }
        mqttClient.publish_disconnect();
    }

    return 0;
}

mqttClient.publish_send(msg);即实现了内容的发布。通常MQTT作为组件存在时，并不是一直处于运行状态的，还是要用到他发布功能的时候就连接上，用完或者不要用的时候就要 mqttClient.publish_disconnect();

---

测试结果

笔者已经把实现的Demo上传到资源了，读者可以自行测试。可以直接作为组件库使用。

本人的测试环境是Jetson Nano B01下搭载英伟达官方镜像Ubuntu20.04.

注意一定要先，安装paho.mqtt.c库哦，安装流程请移步到

Liunx下用C语言实现MQTT的接收与发送(上)_星羽空间-CSDN博客Liunx下用C语言实现MQTT的接收与发送https://blog.csdn.net/qq_25662827/article/details/122567741

---

本篇文章，最终代码见（5积分，买不了吃亏，买不了上当，绝对值了）：

https://download.csdn.net/download/qq_25662827/77133536https://download.csdn.net/download/qq_25662827/77133536