#!/usr/bin/env perl

use strict;
use warnings;
use Socket qw(TCP_NODELAY);
use IO::Socket;
use IO::Socket::INET;
use IPC::Open2;

$|++;

my @cmd = ('ls', '-l');

my $sock = IO::Socket::INET::->new(
    Listen    => 20,
    LocalAddr => '0.0.0.0',
    LocalPort => 10101,
    Proto     => 'tcp',
    Reuse     => 1,
);

die "Unable to create socket: $!" unless $sock;

$sock->sockopt(TCP_NODELAY, 1);

$SIG{CHLD} = 'IGNORE';

while (1) {        # Go on forever!
    my $connection = $sock->accept();    # Blocking
    my $child = fork();
    unless (defined($child)) {
        $connection->close();        # Not enough resources to fork();
        next;
    }
    if ($child) {
        # I'm the parent
        next;
    } else {
        # I'm the child, I serve this connection
        print "Connection accepted\n";
        print "Starting command...\n";

        my $cmd_pid = open2('<&'.fileno($connection), '>&'.fileno($connection), @cmd);
        unless ($cmd_pid) {
            $connection->close();
            die "command failed!";
        }
        waitpid($cmd_pid, 0);

        print "Closing connection.\n";
        $connection->close();
        exit 0;
    }
}