Subscribe doesn't work

[fullstact69]

MQTT client's publish method has "retain" param. It is true or false.

I change the payload data at publish method.

If "retain" param is true value, subscribe method is getting the changed data every time.
But if "retain" param is false value, subscribe method is not getting the changed data.

How can I resolve this?

[zibuyu1995]

In the MQTT protocol retain is only relevant to whether the device can receive messages after reconnecting.