dns request (python)

import socket
import struct
import binascii
import sys

def readDomainName(dat, off, lvl_ptr = 0):
    got_ptr = False
    ret = ''
    while not got_ptr and ord(dat[off]):
        if ret: ret = ret + '.'
        isptr = struct.unpack('>H', dat[off:off+2])[0]
        if isptr >= 0xc000:
            got_ptr = True
            if lvl_ptr < 5: #avoid inf loops
                ret += readDomainName(dat, isptr & 0x3fff, lvl_ptr+1)[0]
            else: ret += '[depth err]'
            off += 2
        else:
            off2 = off + ord(dat[off]) + 1
            ret += dat[off + 1: off2]
            off = off2
    if not got_ptr and ord(dat[off]) == 0: off += 1 #skip /0
    return ret, off

def getIPv4(dat, off):
    ip = struct.unpack('BBBB', dat[off:off+4])
    strip = '.'.join(str(i) for i in ip)
    return strip, off + 4

DOMAIN = raw_input("Input domain name: ") #'www.google.com'
REM_IP = raw_input("Input DNS server address [8.8.8.8]: ") or '8.8.8.8'
REM_PORT = 53

dmn_parts = DOMAIN.split('.')
dmn_parts_len = ()
values = (0x0123, 0x0100, 1, 0, 0, 0)
for part in dmn_parts:
    values += (len(part), part,)
    dmn_parts_len += (len(part),)
values += (0, 0x0001, 0x0001,)
dmn_parts_fmt = ''.join(['B%ds' for i in xrange(len(dmn_parts_len))])
s = struct.Struct(('>HHHHHH' + dmn_parts_fmt + 'BHH') % dmn_parts_len)
MESSAGE = s.pack(*values)
sock = socket.socket( socket.AF_INET, # Internet
                      socket.SOCK_DGRAM) # UDP
sock.sendto( MESSAGE, (REM_IP, REM_PORT) )
ANSWER, addr = sock.recvfrom( 1024 ) # buffer size is 1024 bytes
h = struct.unpack('>HHHHHH', ANSWER[0:12])
que_n = h[2]
ans_n = h[3]
aut_n = h[4]
add_n = h[5]

print "DNS server:", REM_IP + ":" + str(REM_PORT)
print "Query (UDP):", binascii.hexlify(MESSAGE)
print "Answer from", addr[0] + ":" + str(addr[1]) + ":", binascii.hexlify(ANSWER)
print
print "Transaction ID:", hex(h[0])
print "Flags:", hex(h[1])
print "Questions:", que_n
print "Answer RRs:", ans_n
print "Authority RRs:", aut_n
print "Additional RRs:", add_n
print

#Queries
pos = 12
for i in xrange(que_n):
    name, pos = readDomainName(ANSWER, pos)
    print i + 1, "Query for:", name
    pos += 2 + 2
print
#Answers
for i in xrange(ans_n):
    name, pos = readDomainName(ANSWER, pos)
    if name:
        answ = ''
        type = struct.unpack('>H', ANSWER[pos:pos+2])[0]
        pos += 2 + 2 + 4 + 2
        if type == 0x0001: #A record
            answ, pos = getIPv4(ANSWER, pos)
        elif type == 0x0005: #CNAME
            answ, pos = readDomainName(ANSWER, pos)
        if answ:
            print i + 1, "Answer for", name, "is", answ
        else:
            print i + 1, "Corrupted answer for", name
            break
    else:
        print i + 1, "Corrupted answer"
        break