#!/usr/bin/perl

use 5.010;

use strict;
use warnings;

use IO::Socket;

my $INTERVAL      =  10;
my $MAX_BUFSIZE   = 512;

my $NO_CONTACT    =   0;
my $SENDING       =   1;
my $LOST_CONTACT  =   2;

my $server = '192.168.0.1';

my @server_ports = (8020, 8019, 8008, 8003);
my @sockets      = map {
    my $socket = IO::Socket::INET::->new(
        LocalPort  => $_,
        LocalAddr  => $server,
        Proto      => 'udp',
    ) or die $!;
    $socket;
} @server_ports;
my @states       = ($NO_CONTACT) x @sockets;
my @heartbeats   = (0) x @sockets;
my @counts       = (0) x @sockets;

my $Rbits  = "";
my $Ebits  = "";
vec($Rbits, fileno($_), 1) = 1 for @sockets;
vec($Ebits, fileno($_), 1) = 1 for @sockets;

while (1) {
    select(my $rbits = $Rbits, undef, my $ebits = $Ebits, 1);

    for (my $i = 0; $i < @sockets; $i ++) {
        my $socket    = $sockets[$i];
        my $fileno    = fileno($socket);
        my $state     = $states[$i];
        my $heartbeat = $heartbeats[$i];

        if (vec($ebits, $fileno, 1)) {
            say "Got an error on channel $i. I'm out of here";
            exit 1;
        }

        if (vec($rbits, $fileno, 1)) {
            my $sender = $socket->recv(my $buffer, $MAX_BUFSIZE);
            if (length $buffer) {
                my ($port, $remote) = sockaddr_in($sender);
                $remote = inet_ntoa($remote);
                say "Got HB from $remote:$port";
                $heartbeat = $heartbeats[$i] = time;
                if ($state == $NO_CONTACT) {
                    #
                    # Upgrade the socket now we know the remote
                    #
                    vec($Rbits, fileno($socket), 1) = 0;
                    vec($Ebits, fileno($socket), 1) = 0;
                    undef $sockets[$i];
                    undef $socket;
                    $socket = $sockets[$i] = IO::Socket::INET::->new(
                        LocalPort  => $server_ports[$i],
                        LocalAddr  => $server,
                        PeerAddr   => $remote,
                        PeerPort   => $port,
                        Proto      => 'udp',
                    ) or die $!;
                    vec($Rbits, fileno($socket), 1) = 1;
                    vec($Ebits, fileno($socket), 1) = 1;
                    $state = $states[$i] = $SENDING;
                }
            }  
        }

        #
        # Out of time?
        #
        if ($state == $SENDING && $heartbeat + $INTERVAL < time) {
            say "Channel $i is dead. Bye!";
            exit 1;
        }

        #
        # Send data?
        #
        if ($state == $SENDING) {
            foreach (1 .. int rand 10) {
                my $count = ++$counts[$i];
                say "Send packet $count on channel $i";
                $socket->send($count);
            }   
        }
    }
}
 
__END__