ESP32 WiFi/MQTT断开后自动重连需求：无需外部重启且避免频繁重启

针对ESP32 WiFi连接及MQTT传输时的自动重连需求，以下是无需外部干预、故障恢复后自动上线且避免频繁重启的实现方案：

WiFi自动重连机制 #

• 利用ESP32原生WiFi事件监听，捕获SYSTEM_EVENT_STA_DISCONNECTED断开事件
• 触发重连时采用指数退避算法：初始重试间隔1秒，每次失败后间隔翻倍，最大设为60秒，避免频繁请求路由
• 重连前检查当前WiFi状态，防止重复发起无效连接请求

MQTT自动重连机制 #

• 基于PubSubClient库，在MQTT连接断开时标记状态，主循环中定期检查连接状态
• 仅当WiFi已连接成功时，才尝试MQTT重连，避免依赖未就绪的网络发起无效请求
• MQTT重连同样采用指数退避策略，失败后延长重试间隔，保护MQTT Broker资源

防频繁重启策略 #

• 维护全局失败计数器，记录连续重连失败的次数
• 当连续失败次数达到阈值（示例设为10次），启动1小时长延迟定时器，到期后执行设备重启
• 每次WiFi或MQTT连接成功后，立即重置失败计数器，避免误触发重启

核心代码实现 #

#include <WiFi.h>
#include <PubSubClient.h>

// WiFi配置参数
const char* ssid = "YOUR_WIFI_SSID";
const char* password = "YOUR_WIFI_PASSWORD";
// MQTT配置参数
const char* mqtt_broker = "YOUR_MQTT_BROKER_IP";
const int mqtt_port = 1883;
const char* mqtt_client_id = "ESP32_MQTT_Client";

WiFiClient espClient;
PubSubClient mqtt_client(espClient);

// 重连控制变量
unsigned long wifi_retry_delay = 1000;
unsigned long mqtt_retry_delay = 1000;
unsigned long last_retry_time = 0;
int continuous_fail_count = 0;
const int MAX_FAIL_THRESHOLD = 10;
const unsigned long REBOOT_DELAY = 3600000; // 1小时后重启

// WiFi事件回调函数
void WiFiEventHandler(WiFiEvent_t event) {
  switch(event) {
    case SYSTEM_EVENT_STA_DISCONNECTED:
      Serial.println("WiFi连接断开，启动重连流程");
      continuous_fail_count++;
      break;
    case SYSTEM_EVENT_STA_CONNECTED:
      Serial.println("WiFi连接成功");
      continuous_fail_count = 0;
      wifi_retry_delay = 1000; // 重置退避间隔
      break;
    default:
      break;
  }
}

// MQTT重连函数
bool reconnectMQTT() {
  if (mqtt_client.connect(mqtt_client_id)) {
    Serial.println("MQTT连接成功");
    // 订阅业务主题（按需添加）
    mqtt_client.subscribe("device/data/recv");
    mqtt_retry_delay = 1000;
    continuous_fail_count = 0;
    return true;
  } else {
    Serial.print("MQTT连接失败，错误码: ");
    Serial.println(mqtt_client.state());
    // 指数退避，最大间隔60秒
    mqtt_retry_delay = min(mqtt_retry_delay * 2, 60000UL);
    continuous_fail_count++;
    return false;
  }
}

// WiFi重连函数
void reconnectWiFi() {
  if (WiFi.status() != WL_CONNECTED) {
    Serial.printf("尝试连接WiFi，延迟: %d秒\n", wifi_retry_delay / 1000);
    WiFi.begin(ssid, password);
    // 等待5秒超时
    unsigned long start_time = millis();
    while (WiFi.status() != WL_CONNECTED && millis() - start_time < 5000) {
      delay(500);
      Serial.print(".");
    }
    if (WiFi.status() != WL_CONNECTED) {
      wifi_retry_delay = min(wifi_retry_delay * 2, 60000UL);
    }
  }
}

void setup() {
  Serial.begin(115200);
  // 注册WiFi事件监听
  WiFi.onEvent(WiFiEventHandler);
  WiFi.begin(ssid, password);
  mqtt_client.setServer(mqtt_broker, mqtt_port);
  // 若需处理MQTT消息，可设置回调函数
  // mqtt_client.setCallback(mqttMessageCallback);
}

void loop() {
  // 检查是否触发重启条件
  if (continuous_fail_count >= MAX_FAIL_THRESHOLD) {
    Serial.println("连续重连失败次数超限，1小时后重启设备");
    delay(REBOOT_DELAY);
    ESP.restart();
  }

  // WiFi重连逻辑
  if (WiFi.status() != WL_CONNECTED) {
    unsigned long now = millis();
    if (now - last_retry_time >= wifi_retry_delay) {
      last_retry_time = now;
      reconnectWiFi();
    }
  } else {
    // MQTT重连逻辑
    if (!mqtt_client.connected()) {
      unsigned long now = millis();
      if (now - last_retry_time >= mqtt_retry_delay) {
        last_retry_time = now;
        reconnectMQTT();
      }
    } else {
      // 保持MQTT客户端心跳
      mqtt_client.loop();
      // 此处添加MQTT数据发送逻辑
      // mqtt_client.publish("device/data/send", "hello world");
    }
  }
}

内容的提问来源于stack exchange，提问作者Ehsanul Karim