本章分为两个部分，腾讯云的连接，以及esp32c3的代码实现

腾讯云配置

1.进入腾讯云控制台的物联网开发平台,这里演示的是企业示例，也可以使用公共示例

2.点击左侧的产品开发新建一个产品，如下：

3.进入刚刚创建的产品添加自定义功能

4.填入信息

5.新建一个设备叫ESP32C3

6.点击刚刚创建的ESP32C3，进入后找到连接设备的五个信息,esp32连接云端的时候需要

7.主题的信息

腾讯云端配置完成

ESP32环境配置

1.进入IDF开发环境，新建工程

2.选择mqtt官方示例工程

3.进入app_main,不适用官方的函数连接MQTT，用自己的连接，下面是连接代码，DHT11的没有给出，写上就可以，属性和刚刚云端设置的标识符一样，云端会自动识别并显示数据

/* MQTT (over TCP) Example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include "esp_system.h"
#include "nvs_flash.h"
#include "esp_event.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"

#include "esp_log.h"
#include "mqtt_client.h"

extern float Temp;
extern float Humi;

#define TX_host "填写刚刚的在云端拿到的五个信息"
#define TX_port 1883
#define TX_client_id "填写刚刚的在云端拿到的五个信息"
#define TX_username "填写刚刚的在云端拿到的五个信息"
#define TX_password "填写刚刚的在云端拿到的五个信息"

static const char *TAG = "mqtt_example";

static void log_error_if_nonzero(const char *message, int error_code)
{
    if (error_code != 0) {
        ESP_LOGE(TAG, "Last error %s: 0x%x", message, error_code);
    }
}

/*
 * @brief Event handler registered to receive MQTT events
 *
 *  This function is called by the MQTT client event loop.
 *
 * @param handler_args user data registered to the event.
 * @param base Event base for the handler(always MQTT Base in this example).
 * @param event_id The id for the received event.
 * @param event_data The data for the event, esp_mqtt_event_handle_t.
 */
static void mqtt_event_handler(void *handler_args, esp_event_base_t base, int32_t event_id, void *event_data)
{
    ESP_LOGD(TAG, "Event dispatched from event loop base=%s, event_id=%" PRIi32 "", base, event_id);
    esp_mqtt_event_handle_t event = event_data;
    esp_mqtt_client_handle_t client = event->client;
    int msg_id;
    switch ((esp_mqtt_event_id_t)event_id) {
    case MQTT_EVENT_CONNECTED:
        ESP_LOGI(TAG, "MQTT_EVENT_CONNECTED");
        msg_id = esp_mqtt_client_publish(client, "/topic/qos1", "data_3", 0, 1, 0);
        ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id);

        msg_id = esp_mqtt_client_subscribe(client, "/topic/qos0", 0);
        ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id);

        msg_id = esp_mqtt_client_subscribe(client, "/topic/qos1", 1);
        ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id);

        msg_id = esp_mqtt_client_unsubscribe(client, "/topic/qos1");
        ESP_LOGI(TAG, "sent unsubscribe successful, msg_id=%d", msg_id);
        break;
    case MQTT_EVENT_DISCONNECTED:
        ESP_LOGI(TAG, "MQTT_EVENT_DISCONNECTED");
        break;

    case MQTT_EVENT_SUBSCRIBED:
        ESP_LOGI(TAG, "MQTT_EVENT_SUBSCRIBED, msg_id=%d", event->msg_id);
        msg_id = esp_mqtt_client_publish(client, "/topic/qos0", "data", 0, 0, 0);
        ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id);
        break;
    case MQTT_EVENT_UNSUBSCRIBED:
        ESP_LOGI(TAG, "MQTT_EVENT_UNSUBSCRIBED, msg_id=%d", event->msg_id);
        break;
    case MQTT_EVENT_PUBLISHED:
        ESP_LOGI(TAG, "MQTT_EVENT_PUBLISHED, msg_id=%d", event->msg_id);
        break;
    case MQTT_EVENT_DATA:
        ESP_LOGI(TAG, "MQTT_EVENT_DATA");
        printf("TOPIC=%.*s\r\n", event->topic_len, event->topic);
        printf("DATA=%.*s\r\n", event->data_len, event->data);
        break;
    case MQTT_EVENT_ERROR:
        ESP_LOGI(TAG, "MQTT_EVENT_ERROR");
        if (event->error_handle->error_type == MQTT_ERROR_TYPE_TCP_TRANSPORT) {
            log_error_if_nonzero("reported from esp-tls", event->error_handle->esp_tls_last_esp_err);
            log_error_if_nonzero("reported from tls stack", event->error_handle->esp_tls_stack_err);
            log_error_if_nonzero("captured as transport's socket errno",  event->error_handle->esp_transport_sock_errno);
            ESP_LOGI(TAG, "Last errno string (%s)", strerror(event->error_handle->esp_transport_sock_errno));

        }
        break;
    default:
        ESP_LOGI(TAG, "Other event id:%d", event->event_id);
        break;
    }
}

static void mqtt_app_start(void)
{
    esp_mqtt_client_config_t mqtt_cfg = {
        .broker.address.uri = CONFIG_BROKER_URL,
    };
#if CONFIG_BROKER_URL_FROM_STDIN
    char line[128];

    if (strcmp(mqtt_cfg.broker.address.uri, "FROM_STDIN") == 0) {
        int count = 0;
        printf("Please enter url of mqtt broker\n");
        while (count < 128) {
            int c = fgetc(stdin);
            if (c == '\n') {
                line[count] = '\0';
                break;
            } else if (c > 0 && c < 127) {
                line[count] = c;
                ++count;
            }
            vTaskDelay(10 / portTICK_PERIOD_MS);
        }
        mqtt_cfg.broker.address.uri = line;
        printf("Broker url: %s\n", line);
    } else {
        ESP_LOGE(TAG, "Configuration mismatch: wrong broker url");
        abort();
    }
#endif /* CONFIG_BROKER_URL_FROM_STDIN */

    esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
    /* The last argument may be used to pass data to the event handler, in this example mqtt_event_handler */
    esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, NULL);
    esp_mqtt_client_start(client);
}

/**
 * @brief 创建自己连接MQTT的user_mqtt_app_start函数
 *
 */
static void user_mqtt_app_start(void)
{
    esp_mqtt_client_config_t mqtt_cfg = {
        .broker.address.hostname = TX_host,
        .broker.address.port = TX_port,
        .broker.address.transport = MQTT_TRANSPORT_OVER_TCP,
        .credentials.client_id = TX_client_id,
        .credentials.username = TX_username,
        .credentials.authentication.password = TX_password,

    };

    esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
    esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, client);
    esp_mqtt_client_start(client);

    char mqtt_publish_data[100]; // 创建足够大的缓冲区

    while (1)
    {
        /*温湿度传感器模块*/
        DHT11(); // 温湿度      

        /*******    微信小程序JSON    ********/
        //  将温湿度 等等 格式化为 JSON
        snprintf(mqtt_publish_data, sizeof(mqtt_publish_data),
                 "{\"temp\":%.2f, \"humi\":%.2f}", Temp, Humi);
        // 发送消息到指定的 MQTT 主题
        const char *topic = "$thing/up/property/VQUP9AFGUJ/DEMO";       //这里就是刚刚得到的主题消息,发布是up,别写错了
        esp_mqtt_client_publish(client, topic, mqtt_publish_data, strlen(mqtt_publish_data), 1, 0);

        /*******    终端显示    ******/
        // 显示读取后的温度数据
        printf("温度 = %.2f\r\n", Temp);
        // 显示读取后的湿度数据
        printf("湿度 = %.2f\r\n", Humi);
        Delay_ms(5000); // 延时
    }
}

void app_main(void)
{
    ESP_LOGI(TAG, "[APP] Startup..");
    ESP_LOGI(TAG, "[APP] Free memory: %" PRIu32 " bytes", esp_get_free_heap_size());
    ESP_LOGI(TAG, "[APP] IDF version: %s", esp_get_idf_version());

    esp_log_level_set("*", ESP_LOG_INFO);
    esp_log_level_set("mqtt_client", ESP_LOG_VERBOSE);
    esp_log_level_set("mqtt_example", ESP_LOG_VERBOSE);
    esp_log_level_set("transport_base", ESP_LOG_VERBOSE);
    esp_log_level_set("esp-tls", ESP_LOG_VERBOSE);
    esp_log_level_set("transport", ESP_LOG_VERBOSE);
    esp_log_level_set("outbox", ESP_LOG_VERBOSE);

    ESP_ERROR_CHECK(nvs_flash_init());
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

    // mqtt_app_start();    //不使用官方的MQTT连接
    user_mqtt_app_start();
}