So if I understand correctly if I set the retain option to true on and MQTT node each time a client subscribes to a topic the server should send the last retained value.
If this is correct I'm doing something wrong. Because on an Arduino Mega on a GSM module I don't seem to recieve these "initial" messages.
However, to prove my theory I downloaded MQTT Explorer on my computer and subscribed to a topic with the retain flag to true and I still didn't recieve the message.
This is a screenshot of the configuration on the node:
This is the configuration on the MQTT Explorer app
And this is the info recieved just after establishing the connection: