def _subscribe(self):
cmd = MAGIC + SUBSCRIBE + self._mac+ PADDING_1 + self._mac_reversed + PADDING_1<EOL>status = self._udp_transact(cmd, self._subscribe_resp)<EOL>if status is not None:<EOL><INDENT>self.last_subscribed = time.time()<EOL>return status == ON<EOL><DEDENT>else:<EOL><INDENT>raise S20Exception(<EOL>"<STR_LIT>".format(self.host))<EOL><DEDENT>
Subscribe to the device.

        A subscription serves two purposes:
        - Returns state (on/off).
        - Enables state changes on the device
          for a short period of time.