def read_header(self):
        """Reads header portion of packet"""
        format = '!HHHHHH'
        length = struct.calcsize(format)
        info = struct.unpack(format,
                self.data[self.offset:self.offset + length])
        self.offset += length

        self.id = info[0]
        self.flags = info[1]
        self.num_questions = info[2]
        self.num_answers = info[3]
        self.num_authorities = info[4]
        self.num_additionals = info[5]
Reads header portion of packet