#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Useqq=1;

my @send= fillbuffer();
my $buf=pack('s*',@send);
print Dumper($buf,length $buf);
#  $ok=$client_socket->syswrite($buf,length $buf);

sub fillbuffer { return ( STX(),0x11,0x12,ETX() ); }
sub STX() { unpack('C',"\002") };
sub ETX() { 3 };