Send play command to receiver command via HTTP post.

def _play(self):
        """Send play command to receiver command via HTTP post."""
        # Use pause command only for sources which support NETAUDIO
        if self._input_func in self._netaudio_func_list:
            body = {"cmd0": "PutNetAudioCommand/CurEnter",
                    "cmd1": "aspMainZone_WebUpdateStatus/",
                    "ZoneName": "MAIN ZONE"}
            try:
                if self.send_post_command(
                        self._urls.command_netaudio_post, body):
                    self._state = STATE_PLAYING
                    return True
                else:
                    return False
            except requests.exceptions.RequestException:
                _LOGGER.error("Connection error: play command not sent.")
                return False