Get an NDEF message from the server. Temporarily connects
        to the default SNEP server if the client is not yet connected.

def _get(self, ndef_message, timeout=1.0):
        """Get an NDEF message from the server. Temporarily connects
        to the default SNEP server if the client is not yet connected.
        """
        if not self.socket:
            try:
                self.connect('urn:nfc:sn:snep')
            except nfc.llcp.ConnectRefused:
                return None
            else:
                self.release_connection = True
        else:
            self.release_connection = False
        try:
            snep_request = b'\x10\x01'
            snep_request += struct.pack('>L', 4 + len(str(ndef_message)))
            snep_request += struct.pack('>L', self.acceptable_length)
            snep_request += str(ndef_message)
            if send_request(self.socket, snep_request, self.send_miu):
                response = recv_response(
                    self.socket, self.acceptable_length, timeout)
                if response is not None:
                    if response[1] != 0x81:
                        raise SnepError(response[1])
                    return response[6:]
        finally:
            if self.release_connection:
                self.close()