#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket;
use IO::Select;
use Socket qw( sockaddr_in inet_ntoa );
# Socket to receive commands
my $controllers_listener = IO::Socket::INET->new(
Proto => 'udp',
LocalPort => 50605,
ReuseAddr => 1,
) or die "new socket: $!";
# Socket for listening to incoming connections
my $clients_listener = IO::Socket::INET->new(
Proto => 'tcp',
LocalPort => 50605,
ReuseAddr => 1,
Listen => 3,
) or die "new socket: $!";
my %clients;
# Use select to coordinate requests
my $sel = IO::Select->new($controllers_listener, $clients_listener);
my @slides = load_slides();
$|++;
my $slide = 0; # Tracks current slide
my %shown_marker_for; # Tracks slides sent to different clients
my %callback_for = ( # Available commands
'first' => sub {
goto_slide(0);
},
'last' => sub {
goto_slide($#slides);
},
'next' => sub {
goto_slide($slide + 1);
},
previous => sub {
goto_slide($slide - 1);
},
show => sub {
my $slide = shift;
goto_slide($slide - 1) if $slide;
},
);
# Main loop
while (my @ready = $sel->can_read()) {
FILEHANDLE:
for my $fh (@ready) {
if ($fh == $clients_listener) { # add new client
my ($socket, $peer) = $clients_listener->accept();
exhaust_input($socket); # ignore input data
$clients{$socket} = [$socket, $peer];
$sel->add($socket);
activity($peer, 'client entered');
# Send the current slide
print_header($socket);
print_slide($socket, $slide);
} ## end if ($fh == $clients_listener)
elsif (exists $clients{$fh}) { # close connection
activity($clients{$fh}[1], 'client exited');
$sel->remove($fh);
$fh->close();
delete $clients{$fh};
}
else { # Command received, via UDP
# Command from controller
my $peer = $fh->recv(my $command_string, 1500)
or next FILEHANDLE;
next FILEHANDLE unless $command_string;
for my $command_line (split /\n+/, $command_string) {
next unless $command_line =~ /\S/;
my ($command, @args) = split /\s+/, $command_line;
activity($peer, "trying command '$command_line'");
$callback_for{$command}->(@args)
if exists $callback_for{$command};
}
} ## end else [ if ($fh == $controllers_listener)
} ## end for my $fh (@ready)
} ## end while (@ready = $sel->can_read...
# Log on STDOUT about what's happening
sub activity {
my ($peer, $msg) = @_;
my ($port, $iaddr) = sockaddr_in($peer);
my $addr = inet_ntoa($iaddr);
print {*STDOUT} "$addr:$port - $msg\n";
return;
}
# Send header to the client
sub print_header {
my ($socket) = @_;
print {$socket} "HTTP/1.1 200 OK\r\n";
print {$socket} "Content-type: text/html\r\n\r\n";
print {$socket} "\n";
} ## end sub print_header
sub hide_slide {
my ($socket, $slide) = @_;
print {$socket} "\n";
}
sub print_slide {
my ($socket, $slide) = @_;
if ($shown_marker_for{$socket}{$slide}) { # just resume
print {$socket} "\n";
}
else {
print {$socket} qq(
$slides[$slide]
);
}
$shown_marker_for{$socket}{$slide} = 1;
} ## end sub print_slide
# Transition function, for each client hides the previous
# and shows the new
sub goto_slide {
my ($new_slide) = @_;
return unless $new_slide =~ /\A\d+\z/mxs;
return unless $new_slide < @slides;
my $old_slide = $slide;
print {*STDOUT} "going to $new_slide from $old_slide\n";
for my $client (values %clients) {
hide_slide($client->[0], $old_slide);
print_slide($client->[0], $new_slide);
}
$slide = $new_slide;
return;
} ## end sub goto_slide
# Eliminate input data coming from clients
sub exhaust_input {
my ($socket) = @_;
my $sel = IO::Select->new($socket);
while ($sel->can_read(0)) {
$socket->sysread(my $input, 1500);
return 0 unless length $input;
}
return 1; # for many reasons...
} ## end sub exhaust_input
# Dummy function, loads test slides after __END__
sub load_slides {
local $/ = "\n----------\n";
chomp(@slides = );
return @slides;
}
__END__
This is slide 1
Here you can find the contents for slide #1. You can insert images:
as well as other elements:
----------
This is slide 2
The contents are completely different here.
----------
This is slide 3
The contents are completely different here, with respect to the other
two pages.
I live here!
####
shell$ netcat -q 0 -u 50605 <<<'next'
shell$ netcat -q 0 -u 50605 <<<'next'
shell$ netcat -q 0 -u 50605 <<<'next'
shell$ netcat -q 0 -u 50605 <<<'first'
shell$ netcat -q 0 -u 50605 <<<'show 2'
shell$ netcat -q 0 -u 50605 <<<'previous'
shell$ netcat -q 0 -u 50605 <<<'last'