idf4.4.4的通配符示例

下面是在 ESP-IDF 4.4.4 中使用 MQTT 通配符的示例代码：

#include <stdio.h>
#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <esp_wifi.h>
#include <esp_event.h>
#include <esp_log.h>
#include <mqtt_client.h>

static const char *TAG = "MQTT_EXAMPLE";

static esp_err_t mqtt_event_handler_cb(esp_mqtt_event_handle_t event)
{
    esp_mqtt_client_handle_t client = event->client;
    int msg_id;
    // your event handling code here
    switch (event->event_id) {
        case MQTT_EVENT_CONNECTED:
            ESP_LOGI(TAG, "MQTT_EVENT_CONNECTED");
            msg_id = esp_mqtt_client_subscribe(client, "home/livingroom/+/temperature", 0);
            ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id);
            msg_id = esp_mqtt_client_subscribe(client, "home/#", 0);
            ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", 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_DISCONNECTED:
            ESP_LOGI(TAG, "MQTT_EVENT_DISCONNECTED");
            break;
        case MQTT_EVENT_SUBSCRIBED:
            ESP_LOGI(TAG, "MQTT_EVENT_SUBSCRIBED, msg_id=%d", event->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_ERROR:
            ESP_LOGI(TAG, "MQTT_EVENT_ERROR");
            if (event->error_handle->error_type == MQTT_ERROR_TYPE_ESP_TLS) {
                ESP_LOGI(TAG, "Last error code reported from esp-tls: 0x%x", event->error_handle->esp_tls_last_esp_err);
                ESP_LOGI(TAG, "Last tls stack error number: 0x%x", event->error_handle->esp_tls_stack_err);
            } else if (event->error_handle->error_type == MQTT_ERROR_TYPE_CONNECTION_REFUSED) {
                ESP_LOGI(TAG, "Connection refused error: 0x%x", event->error_handle->connect_return_code);
            } else {
                ESP_LOGW(TAG, "Unknown error type: %d", event->error_handle->error_type);
            }
            break;
        default:
            ESP_LOGI(TAG, "Other event id:%d", event->event_id);
            break;
    }
    return ESP_OK;
}

static void mqtt_app_start(void)
{
    esp_mqtt_client_config_t mqtt_cfg = {
        .uri = CONFIG_BROKER_URL,
        .event_handle = mqtt_event_handler_cb,
        .username = CONFIG_BROKER_USERNAME,
        .password = CONFIG_BROKER_PASSWORD,
    };
    esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
    esp_mqtt_client_start(client);
}

void app_main()
{
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    ESP_ERROR_CHECK(example_connect());
    mqtt_app_start();
}

在这个示例中，当 ESP32 连接到 MQTT 服务器时，它会订阅 `home/livingroom/+/temperature` 和 `home/#` 这两个主题，其中 `+` 和 `#` 分别代表单个层级和多个层级的通配符。当有消息发布到这些主题时，ESP32 将会收到并调用 `mqtt_event_handler_cb` 函数进行处理。