dns_resolve.py

import os
import re
import socket
import struct

def dns_resolve(host, dnsserver):
    assert isinstance(host, basestring) and isinstance(dnsserver, basestring)
    index = os.urandom(2)
    hoststr = ''.join(chr(len(x))+x for x in host.split('.'))
    data = '%s\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00%s\x00\x00\x01\x00\x01' % (index, hoststr)
    data = struct.pack('!H', len(data)) + data
    address_family = {True:socket.AF_INET6, False:socket.AF_INET}[':' in dnsserver]
    sock = None
    try:
        sock = socket.socket(family=address_family)
        sock.connect((dnsserver, 53))
        sock.sendall(data)
        rfile = sock.makefile('rb')
        size = struct.unpack('!H', rfile.read(2))[0]
        data = rfile.read(size)
        iplist = re.findall('\xC0.\x00\x01\x00\x01.{6}(.{4})', data)
        return ['.'.join(str(ord(x)) for x in s) for s in iplist]
    except Exception, e:
        raise
    finally:
        if sock:
            sock.close()

print dns_resolve('www.youtube.com', '8.8.8.8')