void PubSubClient::disconnect() {
   if (!connected())
     return;

   MQTT::Disconnect discon;
   discon.send(*_client);
   _client->stop();
   lastInActivity = lastOutActivity = millis();
}
void PubSubClient::disconnect() {
   MQTT::Disconnect discon;
   discon.send(_client);
   _client.stop();
   lastInActivity = lastOutActivity = millis();
}