官方的最新文档地址，
https://docs.espressif.com/projects/esp-idf/zh_CN/latest/index.html
持续更新，新的文档推出了很多新的案例。
现在记录下我学习MQTT的过程，希望可以帮助到一些朋友和自己。
官方的案例写的很好，我直接把官方的案例做一个说明。加上链接WiFi的代码
本文默认您已经知道mqtt的相关知识，我前面有一篇写的emq。
emq官方有升级，请安装时注意。
EMQ 安装与部署 @a.宏万
首先看官方的说明
https://docs.espressif.com/projects/esp-idf/zh_CN/latest/api-reference/protocols/mqtt.html#
本文选择 TCP协议
链接wifi
ESP_ERROR_CHECK( esp_event_loop_init(event_handler, NULL) ); wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT(); ESP_ERROR_CHECK( esp_wifi_init(&cfg) ); ESP_ERROR_CHECK( esp_wifi_set_storage(WIFI_STORAGE_RAM) ); ESP_ERROR_CHECK( esp_wifi_set_mode(WIFI_MODE_STA) ); wifi_config_t sta_config = { .sta = { .ssid = "",//wifi名称 .password = "",//密码 .bssid_set = false } }; ESP_ERROR_CHECK( esp_wifi_set_config(WIFI_IF_STA, &sta_config) ); ESP_ERROR_CHECK( esp_wifi_start() ); ESP_ERROR_CHECK( esp_wifi_connect() );
注册mqtt
const esp_mqtt_client_config_t mqtt_cfg = { .host = "*.*.*.*",//服务器IP地址 默认端口 1883 }; 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_ERROR_CHECK(esp_mqtt_client_start(client));
以上两端代码就可以链接到mqtt服务器了。
事件监控代码
mqtt_event_handler
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=%d", base, event_id); mqtt_event_handler_cb(event_data); }
事件实现代码
mqtt_event_handler_cb
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_context_t *context = event->context; switch (event->event_id) { case MQTT_EVENT_CONNECTED://连接事件 ESP_LOGI(TAG, "MQTT_EVENT_CONNECTED"); msg_id = esp_mqtt_client_publish(client, "/topic/qos1", "data_3", 0, 1, 0);//发布 ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id); msg_id = esp_mqtt_client_subscribe(client, "/topic/qos0", 0);//订阅 ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id); msg_id = esp_mqtt_client_subscribe(client, "/topic/qos1", 1);//订阅 ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id); msg_id = esp_mqtt_client_unsubscribe(client, "/topic/qos1");//取消订阅 ESP_LOGI(TAG, "sent unsubscribe successful, msg_id=%d", msg_id); break; case MQTT_EVENT_DISCONNECTED://断开事件 ESP_LOGI(TAG, "MQTT_EVENT_DISCONNECTED"); break; case MQTT_EVENT_SUBSCRIBED://订阅事件 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);//发布 ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id); break; case MQTT_EVENT_UNSUBSCRIBED://未订阅事件 ESP_LOGI(TAG, "MQTT_EVENT_UNSUBSCRIBED, msg_id=%d", event->msg_id); break; case MQTT_EVENT_PUBLISHED://发布的事件 ESP_LOGI(TAG, "MQTT_EVENT_PUBLISHED, msg_id=%d", event->msg_id); break; case MQTT_EVENT_DATA://数据事件 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://错误事件 ESP_LOGI(TAG, "MQTT_EVENT_ERROR"); break; case MQTT_EVENT_BEFORE_CONNECT: //事件在连接之前发生 break; default: ESP_LOGI(TAG, "Other event id:%d", event->event_id); break; } return ESP_OK; }
esp-idf mqtt 提供了很多事件
代码中默认订阅的主题是 ：/topic/qos0
现在我们使用mqtt程序给这个主题发布消息
使用串口链接软件 链接到esp32 查看打印内容
测试成功！
这里多说几句，如果你的设备可以链接mqtt了基本上就啥都可以干了。比如开灯。关灯。
远程开关电脑，向日葵的开机棒基本上也就是这个原理。
远程开关，温度传感器。火焰探测。这些都是可以的。
mqtt最大支持的传输可以达到100多兆，你都可以用设备传输图像了。
可以更新本地wifi链接，设备重启。
凡是可以通过消息对话搞定的都可以试试。
下面是完整代码。
#include#include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "esp_system.h" #include "esp_spi_flash.h" #include "esp_wifi.h" #include "esp_event.h" #include "esp_event_loop.h" #include "nvs_flash.h" #include "driver/gpio.h" #include "esp_log.h" #include "mqtt_client.h" static const char *TAG = "MQTT_EXAMPLE"; esp_err_t event_handler(void *ctx, system_event_t *event) { return ESP_OK; } 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_context_t *context = event->context; switch (event->event_id) { case MQTT_EVENT_CONNECTED://连接事件 ESP_LOGI(TAG, "MQTT_EVENT_CONNECTED"); msg_id = esp_mqtt_client_publish(client, "/topic/qos1", "data_3", 0, 1, 0);//发布 ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id); msg_id = esp_mqtt_client_subscribe(client, "/topic/qos0", 0);//订阅 ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id); msg_id = esp_mqtt_client_subscribe(client, "/topic/qos1", 1);//订阅 ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id); msg_id = esp_mqtt_client_unsubscribe(client, "/topic/qos1");//取消订阅 ESP_LOGI(TAG, "sent unsubscribe successful, msg_id=%d", msg_id); break; case MQTT_EVENT_DISCONNECTED://断开事件 ESP_LOGI(TAG, "MQTT_EVENT_DISCONNECTED"); break; case MQTT_EVENT_SUBSCRIBED://订阅事件 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);//发布 ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id); break; case MQTT_EVENT_UNSUBSCRIBED://未订阅事件 ESP_LOGI(TAG, "MQTT_EVENT_UNSUBSCRIBED, msg_id=%d", event->msg_id); break; case MQTT_EVENT_PUBLISHED://发布的事件 ESP_LOGI(TAG, "MQTT_EVENT_PUBLISHED, msg_id=%d", event->msg_id); break; case MQTT_EVENT_DATA://数据事件 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://错误事件 ESP_LOGI(TAG, "MQTT_EVENT_ERROR"); break; case MQTT_EVENT_BEFORE_CONNECT: //事件在连接之前发生 break; default: ESP_LOGI(TAG, "Other event id:%d", event->event_id); break; } return ESP_OK; } 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=%d", base, event_id); mqtt_event_handler_cb(event_data); } void app_main() { ESP_LOGI(TAG, "[APP] Startup.."); ESP_LOGI(TAG, "[APP] Free memory: %d 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_TCP", ESP_LOG_VERBOSE); esp_log_level_set("TRANSPORT_SSL", 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()); tcpip_adapter_init(); ESP_ERROR_CHECK(esp_event_loop_create_default()); ESP_ERROR_CHECK( esp_event_loop_init(event_handler, NULL) ); wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT(); ESP_ERROR_CHECK( esp_wifi_init(&cfg) ); ESP_ERROR_CHECK( esp_wifi_set_storage(WIFI_STORAGE_RAM) ); ESP_ERROR_CHECK( esp_wifi_set_mode(WIFI_MODE_STA) ); wifi_config_t sta_config = { .sta = { .ssid = "xz220", .password = "www", .bssid_set = false } }; ESP_ERROR_CHECK( esp_wifi_set_config(WIFI_IF_STA, &sta_config) ); ESP_ERROR_CHECK( esp_wifi_start() ); ESP_ERROR_CHECK( esp_wifi_connect() ); const esp_mqtt_client_config_t mqtt_cfg = { .host = "*.*.*.*", }; 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_ERROR_CHECK(esp_mqtt_client_start(client)); gpio_set_direction(GPIO_NUM_2, GPIO_MODE_OUTPUT); int level = 0; while (true) { gpio_set_level(GPIO_NUM_2, level); level = !level; vTaskDelay(300 / portTICK_PERIOD_MS); } }