#!/usr/bin/perl
use strict;
use warnings;

use Socket;
use constant LINE_LEN => 24;

my $NUM_CHLDS = 5; # Five children

my ($parent, $child) = ();
my (@pids,$line) = ();
my @chld_fh = ();
my @par_fh = ();

print "Forking...";
for(0 .. $NUM_CHLDS) {
  $pids[$_] = { child_fh  => 0,
                parent_fh => 0,
                pid       => 0
              };
  socketpair($pids[$_]->{child_fh},$pids[$_]->{parent_fh},
    AF_UNIX,SOCK_STREAM,PF_UNSPEC) or die "socketpair at $_: $!\n";

  unless(($pids[$_]->{pid} = fork())) {
    # Child
    die "cannot fork at $_: $!" unless defined $pids[$_]->{pid};
    close $pids[$_]->{child_fh};
    print "$$: Getting line\n";
    sysread($pids[$_]->{parent_fh},$line,LINE_LEN);
    $line = "$$: " . reverse $line . int(rand(10));
    print "$$: Sending line back\n";
    syswrite($pids[$_]->{parent_fh},$line,LINE_LEN);
    close $child;
    syswrite($pids[$_]->{parent_fh},$line,LINE_LEN);
    close $child;
    exit;
  }
  print "1..";
}

print "\n";

# Parent
#
chomp($line = <STDIN>);
print "$$: Got string, writing\n";
for(0 .. $NUM_CHLDS)
{
  close $pids[$_]->{parent_fh};
  syswrite($pids[$_]->{child_fh},$line,LINE_LEN);
}


print "$$: Wrote, waiting\n";
sleep 1; # For fun

for(0 .. $NUM_CHLDS)
{
  sysread($pids[$_]->{child_fh},$line,LINE_LEN);
  print "Parent pid $$ just read: '$line'\n";
  close $pids[$_]->{child_fh};
}
wait;