How to get the value of a mqtt subscription without a value change

Using Arduino Programming Questions
#1

Is it possible to get the value of a mqtt subscription without a subscription value change?

Basically, I want to know the value of a mqtt subscription at the beginning of my program. I have not been able to find any commands that will give me the output of a subscription without a value change of the subscription. This is the code I am using now.

Adafruit_MQTT_Subscribe *subscription;
  while ((subscription = mqtt.readSubscription(5000))) {
    Serial.print(F("Received Alert Control Data "));
    if (subscription == &alertsButton) {
      if (((char *)alertsButton.lastread) == "ON ") {
        Serial.println(F("(Alerts Active) "));
        alertsA = 1;
      } else {
        Serial.println(F("(Alerts Not Active) "));
        alertsA = 0;
      }
    newSubscription = 1;
    }
  }

Thanks in advance!

#2

I have not been able to find any commands that will give me the output of a subscription without a value change of the subscription.

If nothing/no one has subscribed, what, exactly, are you expecting to get?

#3

I have the same problem. I use ioBroker as server and there are some values stored that I want to read when the ESP8266 starts, but I have to change the stored value in ioBroker to trigger this. Then I receive the message at the ESP.

To explain my approach: I want to meter my gas counter with a reed switch. At start I want to read the current value from ioBroker, then add the metered values and send it back to ioBroker.

Edit: I found a solution. I use the PubSubClient and there is a retained parameter that sends back the current value stored in ioBroker.

#4