sub readn
{
   my ($socket, $bytes ) = @_;
   my $offset = 0;
   
   my $buf = "";
   while ($offset < $bytes)
   {
      my $nread;
      my $nleft = $bytes-$offset;
      
      $nread = sysread($socket,$buf,$nleft,$offset);
      kill 'USR1',$$ unless (defined $nread);  ## undef is like -1 unix return
      last if ($nread ==0);                    ## EOF
      
      $offset += $nread;
   }
   
  # print "length of received buff=",length $buf,"\n";
  # print $buf;
   return $buf;
}