Unfortunately I can not explain how my simple system works, I try again:
master A (Arduino Mega + eth shield) >>> via Bridge >>> slave B (wemosD1)
master sends values to the slave via Bridge
the values sent every two seconds to the slave regulate the times, variables, on / off the boiler (a sort of PWM control).
if the value received by the slave is 0, the boiler is off, if it receives the value 198 the boiler is always on. If the value sent is, for example, 99, the boiler is on at 50%. If at this point there is a loss of wifi connection (or for any other reason connected to the network) the boiler remains on at 50% even if the master is sent the value 0. This is not good. The OTA you mentioned for now is not implemented. I need, on the slave side, that if a connection loss occurs (of any kind, due to access point failure, to the server crash that I have at home then not cluod, etc. etc.) the value that is expected to arrive from the master goes to 0 (and therefore turns off the boiler) until a subsequent connection reset. In another way I do not know how to explain