#!/usr/bin/perl

# Perl SOPW 
# https://www.perlmonks.org/?node_id=11151665

use strict;
use warnings;
$|=1; #Turn stdio buffering off

use IO::Socket;
use POSIX qw(sys_wait_h);
use constant LISTEN_PORT => 8081;

my $socket = IO::Socket::INET->new
              ( LocalPort => 8081,
                Proto     => 'tcp',
                Type      => SOCK_STREAM,
                Reuse     => 1,
                Listen    => 10,
               )
           or
die "Could not open port 8081!";

my $client;

while (1)
{
   $client = $socket->accept() || next; #accept() is not re-entrant
                                        #loop if error
   
   my $pid = fork();
   die "Bad Fork!" unless defined $pid;
   
   if ($pid == 0 )  # child
   {
       close ($socket); # children don't listen for new connections
       
       my $line;
       my @buff;
       
       while (defined ($line=<$client>) and $line !~ /^\s*$/)
       {
          push @buff, $line;
       }
             
       my $time = time();
       print "INCOMING from a Client Connection at $time\n";
       
       do_command(\@buff);
       
       exit(0);
   }
   else              # parent
   {
       close ($client); #wait for next client request
   }
}

sub do_command  
{
    my $buff = shift;
    
    print $client "START\n";
    print $client "$_" for @$buff;  #just loopback lines to client
    print $client "END\n";
    $client->flush();
}