def hashret(self):
        """DEV: returns a string that has the same value for a request and its answer."""
        if 'PositiveResponse' in self.services[self.service]:
            return struct.pack('B', self.service - 0x40)
        elif self.service == 0x7f:
            return struct.pack('B', self.requestServiceId)
        else:
            return struct.pack('B', self.service)
DEV: returns a string that has the same value for a request and its answer.