visuino, controllino and MQTT

hi, i have to do a program that i can control "CONTROLLINO" from the mqtt server adafruit.
for doing this i'm using visuino to program the comuniction from the server to the controllino, with the simple comunication program i don't have problem, but when i want to do something else with an input from the server problems arise.
one idea is send the input to the serial of controllino and then modify the program that visuino send and say " if (serial.read() == 1) do something..." (this isn't the correct programmation string but is only for examples) but it not work, also if i write in the loop "Serial.println(Serial.read());" on the serial it only read "-1".
how can i solve this problem and something with the input of the mqtt server??
i'm sorry for my bad english and i hope that i made myself understood.

Nicolamarc:
i hope that i made myself understood.

Not really. Getting -1 from serial.Read means that there was nothing to get - take a look at serial.Available.

in the serial.available if i send something from the server or not on the serial ther is always nothing (0).
it means that if i send a character from the server to the serial it not pass through the serial.availale or something like that?