#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket;
use threads;
use Thread::Queue;

#get the port to bind to or default to 8000
my $port = $ARGV[0] || 8000;

# a hash to record client machines and thread queue for internal comunication
my %clients;
my $queue = Thread::Queue -> new;
my $monitor = threads->create ("monitor", $queue);

#ignore child processes to prevent zombies
$SIG{CHLD} = 'IGNORE';

#create the listen socket
my $listen_socket = IO::Socket::INET->new(LocalPort => $port,
                                          Listen => 10,
                                          Proto => 'tcp',
                                          Reuse => 1);
#make sure we are bound to the port
die "Cant't create a listening socket: $@" unless $listen_socket;

warn "Server ready. Waiting for connections on $port ... \n";

#wait for connections at the accept call
while (my $connection = $listen_socket->accept) {
    # spawn a thread to handle the connection
    my $child = threads->create ("read_data", $queue, $connection);
}

sub read_data {
    # accept data from the socket and put it on the queue
    my ($queue, $socket) = @_;
    while (<$socket>) {
        print "listener got: $_";
        $queue -> enqueue(time." $_");
    }
}

sub monitor {
    my $queue = shift;
    while (1) {
        while ($queue -> pending) {
            my $data = $queue -> dequeue;
            print "monitor got: $data";
            $data =~ /(\d+) Heartbeat from (\S+) next one in (\d+) minutes/;
            my $time   = $1;
            my $client = $2;
            my $cycle  = $3;
            if (defined $clients{$client} and $clients{$client} -> [0] eq 'NAK') {
                print "$client sent a beat again\n";
            }
            $clients{$client} = [ 'OK', $time + $cycle * 60 ];
        }
        for my $client (keys %clients) {
            next if $clients{$client}->[0] eq 'NAK';
            next if $clients{$client}->[1] > time;
            print "$client missed a heartbeat, expected at $clients{$client}->[1], now it is ".time."\n";
            $clients{$client}->[0] = 'NAK';
        }
        sleep 30;
    }
}