Following your suggestion I did check both bytes value (inverted and not inverted) txed by the pic 18f2620, removing everything and using a terminal connected to the pic in place of the esp8266. Well both bytes are txed correctly! This esclude the pic as responsible for such a wierd behavior and leave the esp8266 (the server) and the android (the client) as the probable responsible.

Next step is to write a small vb program using socket to act as a client and verify what the esp send out. I will post the result soon.

Alberto