sub decode_7bit {
     my ($ud, $len) = @_;
     my ($msg,$bits);
     my $cnt=0;
     $ud = $ud || "";
     $len = $len || 0;
     $msg = "";
     my $byte = unpack('b8', pack('H2', substr($ud, 0, 2)));
     while (($cnt<length($ud)) && (length($msg)<$len)) {
          my $c = pack('b7', substr($byte,0,8));
          $msg.= $c;
          $byte = substr($byte,7,length($byte)-7);
          if ( (length( $byte ) < 7) ) {
               $cnt+=2;
               $byte = $byte.unpack('b8', pack('H2', substr($ud, $cnt, 2)));
          }
     }
return $msg;
}