def previous_track(self):
        """Send previous track command to receiver command via HTTP post."""
        # Use previous track button only for sources which support NETAUDIO
        if self._input_func in self._netaudio_func_list:
            body = {"cmd0": "PutNetAudioCommand/CurUp",
                    "cmd1": "aspMainZone_WebUpdateStatus/",
                    "ZoneName": "MAIN ZONE"}
            try:
                return bool(self.send_post_command(
                    self._urls.command_netaudio_post, body))
            except requests.exceptions.RequestException:
                _LOGGER.error(
                    "Connection error: previous track command not sent.")
                return False
Send previous track command to receiver command via HTTP post.