in wireshark, it shows the Query name like "3.www.6.google.3.com"

I think wireshark is being helpful, and showing the label lengths in human readable form, using '.' as a separator (it won't, after all, appear in any label !)

This is a little crude:

  sub show {
    return join('', map { ord($_) > 0x3F ? $_ : sprintf('\\x%02X', ord
+($_))
                        } split(//, $_[0])) ;
  } ;

  my $hostname = 'much.ado.about.not.alot.org' ;
  my @labels = split(/\./, $hostname) ;
  my $n = scalar(@labels) ;
  my $question = pack("(C/a*)$n C n2", @labels, 0, 1, 1) ;

  print "\"", show($question), "\"\n" ;
[download]

but gives:

  "\x04much\x03ado\x05about\x03not\x04alot\x03org\x00\x00\x01\x00\x01"

which looks right to me.