本次连接使用的是mqtt的官方公共服务器，前提是要先链接wifi

注意：1.mqtt服务器发给esp32的消息，中间没有/0,使用“%s”这种格式打印的数据会自动往后打印，直到遇见/0,解决方法是

ESP_LOGI(TAG_MQTT,"topic->%.*s",mqtt_data->topic_len,mqtt_data->topic);

定长打印，根据参数里面的长度。

2.消息发送时使用strlen可以获取字符串或者数组的真实大小，不会发送数组的闲杂空位

snprintf(data,sizeof(data),"{data :%d}",a);
esp_mqtt_client_publish(client_handle,MQTT_TOPIC2,data,strlen(data),1,0);

#include <stdio.h> #include "mqtt_client.h" #include "esp_log.h" #include "esp_wifi.h" #include "nvs_flash.h" #include "esp_event.h" #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "freertos/semphr.h" #include <string.h> #define mqtt_url "mqtt://broker-cn.emqx.io" #define mqtt_server_port 1883 #define mqtt_client_id "esp32s3_20260118" #define mqtt_username "esp32s3" #define mqtt_password "esp32s3_password" #define MQTT_TOPIC1 "/topic/esp32_0118" #define MQTT_TOPIC2 "/topic/mqttx_0118" #define TAG_MQTT "TAG_MQTT" #define TAG "STA" #define TAG2 "IP" #define SSID "Redmi" #define PASSWORD "123456789" TaskHandle_t mqtt_task_handel=NULL; //mqtt服务句柄 esp_mqtt_client_handle_t client_handle=NULL; QueueHandle_t esp32_wifi_sem=NULL; //声明mqtt发送消息的任务函数 void mqtt_send_task(); //wifi的事件回调函数 void wifi_cb(void* event_handler_arg,esp_event_base_t event_base,int32_t event_id,void* event_data){ if(event_base==WIFI_EVENT){ switch (event_id) { case WIFI_EVENT_STA_START://开启sta模式成功 esp_wifi_connect();//链接路由器 break; case WIFI_EVENT_STA_CONNECTED://成功连接到路由器 ESP_LOGI(TAG,"esp32s3 connected wifi"); break; case WIFI_EVENT_STA_DISCONNECTED://断开连接 ESP_LOGI(TAG,"esp32s3 disconnected wifi"); esp_wifi_connect(); break; default: break; } } else if (event_base==IP_EVENT) { switch (event_id) { case IP_EVENT_STA_GOT_IP: ESP_LOGI(TAG2,"esp32 got ip,connnecet success"); //释放二进制信号量，开启mqtt服务 xSemaphoreGive(esp32_wifi_sem); break; default: break; } } } //mqtt的事件回调函数 void mqtt_event_cb(void* event_handler_arg,esp_event_base_t event_base,int32_t event_id,void* event_data){ esp_mqtt_event_handle_t mqtt_data=(esp_mqtt_event_handle_t)event_data; switch (event_id) { case MQTT_EVENT_CONNECTED: ESP_LOGI(TAG_MQTT,"esp32 connect mqttserver"); //qos 是订阅的服务的级别，0表示无回应，1表示有，2表示一定有回应 esp_mqtt_client_subscribe_single(client_handle,MQTT_TOPIC1,1); break; case MQTT_EVENT_DISCONNECTED: ESP_LOGI(TAG_MQTT,"esp32 disconnect mqttserver"); break; case MQTT_EVENT_PUBLISHED: ESP_LOGI(TAG_MQTT,"esp32 recive mqttserver publish ack"); break; case MQTT_EVENT_SUBSCRIBED: ESP_LOGI(TAG_MQTT,"esp32 recive mqttserver subscribe ack"); break; case MQTT_EVENT_DATA: // ESP_LOGI(TAG_MQTT,"esp32 recive mqttserver data--------"); // ESP_LOGI(TAG_MQTT,"topic->%s",mqtt_data->topic); // ESP_LOGI(TAG_MQTT,"data->%s",mqtt_data->data); ESP_LOGI(TAG_MQTT,"esp32 recive mqttserver data--------"); ESP_LOGI(TAG_MQTT,"topic->%.*s",mqtt_data->topic_len,mqtt_data->topic); ESP_LOGI(TAG_MQTT,"data->%.*s",mqtt_data->data_len,mqtt_data->data); break; default: break; } } //mqtt配置函数 void mqtt_client_start(){ esp_mqtt_client_config_t mqtt_config={ .broker.address.uri=mqtt_url, .broker.address.port=mqtt_server_port, .credentials.client_id=mqtt_client_id, .credentials.username=mqtt_username, .credentials.authentication.password=mqtt_password, }; client_handle=esp_mqtt_client_init(&mqtt_config); esp_mqtt_client_register_event(client_handle,ESP_EVENT_ANY_ID,mqtt_event_cb,NULL); esp_mqtt_client_start(client_handle); } //mqtt发送消息的任务函数 void mqtt_send_task(){ //阻塞等待信号量 xSemaphoreTake(esp32_wifi_sem,portMAX_DELAY); //开启mqtt服务 mqtt_client_start(); char data[32]={0}; uint8_t a=0; while(1){ //strlen是实际大小，sizeof是数组定义的大小 snprintf(data,sizeof(data),"{data :%d}",a); esp_mqtt_client_publish(client_handle,MQTT_TOPIC2,data,strlen(data),1,0); a++; vTaskDelay(pdMS_TO_TICKS(1000)); } } void app_main(void) { //创建二进制信号量 esp32_wifi_sem=xSemaphoreCreateBinary(); //初始化nvs，后续会用来保存wifi的账号密码 nvs_flash_init(); //初始化网络接口（TCP/IP 协议栈相关） esp_netif_init(); //创建创建默认事件循环机制 esp_event_loop_create_default(); //创建默认的 STA（站点）网络接口对象。 esp_netif_create_default_wifi_sta(); //按照默认配置，初始化wifi的操作 wifi_init_config_t cfg=WIFI_INIT_CONFIG_DEFAULT(); esp_wifi_init(&cfg); //向事件循环里面加入回调函数，有对应事件发生时会自动调用回调函数 esp_event_handler_register(WIFI_EVENT,ESP_EVENT_ANY_ID,wifi_cb,NULL);//sta，数据链路层· //获取到ip，网络层 esp_event_handler_register(IP_EVENT,IP_EVENT_STA_GOT_IP,wifi_cb,NULL); //初始化 wifi_config_t，设置安全阈值和 PMF 能力。 wifi_config_t conf={ .sta.threshold.authmode=WIFI_AUTH_WPA2_PSK, .sta.pmf_cfg.capable=true, .sta.pmf_cfg.required=false, }; memset(conf.sta.ssid,0,strlen(SSID)); memcpy(conf.sta.ssid,SSID,strlen(SSID)); memset(conf.sta.password,0,strlen(PASSWORD)); memcpy(conf.sta.password,PASSWORD,strlen(PASSWORD)); esp_wifi_set_config(WIFI_IF_STA,&conf); esp_wifi_set_mode(WIFI_MODE_STA); //启动 Wi‑Fi，开始连接流程 esp_wifi_start(); //创建发送消息的任务 xTaskCreatePinnedToCore(mqtt_send_task,"mqtt_send_task",4096,NULL,2,&mqtt_task_handel,1); }