sub _get_addr {
   my($sock,$addr_str, $multi) = @_;
   my @addr;
   if ($multi && $addr_str !~ /^\d+(?:\.\d+){3}$/) {
      (undef, undef, undef, undef, @addr) = gethostbyname($addr_str);
   } else {
      my $h = inet_aton($addr_str);
      push(@addr, $h) if defined $h;
   }
   @addr;
}