use strict;
use warnings;

use IO::Socket::INET qw( SOL_SOCKET SO_REUSEADDR );
use Fcntl qw( F_GETFL F_SETFL O_NONBLOCK );

my $port = 54321;

my $socket = IO::Socket::INET->new(
    Proto     => 'udp',
    LocalPort => $port,
    LocalAddr => '127.0.0.1'
);

die "Unable to bind to 127.0.0.1:$port: $!\n" unless $socket;

setsockopt( $socket, SOL_SOCKET, SO_REUSEADDR, 1 );

stop_blocking( $socket );

$SIG{CHLD} = 'IGNORE';

my $pid = fork; die "Could not fork: $!\n" unless defined $pid;

exec( $^X, 'mon2.pl', $port ) if ( $pid == 0 );

$| = 1;

while ( kill(0, $pid) ) {
    my $addr = recv( $socket, my $time, 1024, 0 ) or select '','','',0.015;

    printf "\rProgress: %s", $time;
}

print "\nAll done.\n";

sub stop_blocking {
    my $socket = shift;

    if ($^O eq 'MSWin32') {
        my $flag = 1; ioctl($socket, 0x8004667e, \$flag);
    }
    else {
        my $flags;
        $flags = fcntl($socket, F_GETFL, 0)
           or die "could not getfl: $!\n";
        $flags = fcntl($socket, F_SETFL, $flags | O_NONBLOCK)
           or die "could not setfl: $!\n";
    }
}