void reconnect() //MQTT连接订阅函数
{

if (client.connected()) {
   return;
  }

  Serial.print(F("Connecting to MQTT... "));

  int8_t ret;
  uint8_t retries = 3;

  while (!client.connect(MQTT_CLIENT_ID, MQTT_USERNAME,MQTT_PASSWORD)) { // connect will return true for connected
     // Serial.println(connectErrorToString(client.state()));
      Serial.println(F("Retrying MQTT connection in 5 seconds..."));
      client.disconnect();
      delay(5000);  // wait 5 seconds
      retries--;
      if (retries == 0) {
        // basically die and wait for WDT to reset me
        while (1);
      }
      yield();
  }
  Serial.println(F("Success!"));
  // 订阅主题
  client.subscribe(TOPIC1);