Добрый день.
https://wirenboard.com/wiki/MQTT#.D0.A1.D1.82.D1.80.D1.83.D0.BA.D1.82.D1.83.D1.80.D0.B0_.D1.81.D0.BE.D0.BE.D0.B1.D1.89.D0.B5.D0.BD.D0.B8.D1.8F_.E2.80.94_.D0.BA.D0.BE.D0.BC.D0.B0.D0.BD.D0.B4.D1.8B_.D0.BD.D0.B0_.D0.B8.D0.B7.D0.BC.D0.B5.D0.BD.D0.B5.D0.BD.D0.B8.D0.B5_.D1.81.D0.BE.D1.81.D1.82.D0.BE.D1.8F.D0.BD.D0.B8.D1.8F
Обратите внимание - что для изменения надо писать в /on а читать состояние - просто из топика.