sub write_binary {
  my $fh = shift;
  my $data = shift;
  print $fh unpack("H*", $data), "\n";
}

sub read_binary {
  my $fh = shift;
  my $line = <$fh>;
  chomp;
  return pack("H*", $line);
}

##</code><code>##

my $server = ...;

$server->send_message("Hello");
...
$msg = $server->receive_message();
...