#!/usr/bin/perl

use strict;
use warnings;

use IO::Poll qw(POLLIN POLLHUP POLLERR);
use IO::Socket;

### Behavior of SIGHUP handler.
#
# 0 = print string and nothing else. Errno = "Interrupted system call". Expected behaviour.
# 1 = same as 0 plus open/close of filehandle. Errno = "Inappropriate ioctl for device" regardless of contents in file.
# 2 = same as 1 plus reading a line from file into scalar before closing. If file is empty, then errno is empty. Otherwise, Errno = "Bad file descriptor"
# 3 = same as 2 but setting $/ to undef, reading until end of file into scalar. Errno is emtpy regardless of contents in file.
# 4 = Similar to 2/3 but reading file into an array. Errno is empty regardless of contents in file.
#
my $behaviour = 0;

### Variables you might want to change.
my $file = "file.txt";
my $poll_timeout = 5;

my $handle;
my $pret;
my $readbuffer;
my $rret;
my $string;

my @ready;
my @strings;

unless (-r $file) {
   print "File \"$file\" is not readable...\n";
   exit 1;
}

sub SIGHUP_handler {
   print "Got SIGHUP...\n";

   if ($behaviour == 1) {
   open(FILE, $file);
   close FILE;
   }

   elsif ($behaviour == 2) {
   open(FILE, $file);
   $string = <FILE>;
   close FILE;
   }

   elsif ($behaviour == 3) {
   open(FILE, $file);
   undef $/;
   $string = <FILE>;
   close FILE;
   }

   elsif ($behaviour == 4) {
   open(FILE, $file);
   @strings = <FILE>;
   close FILE;
   }
}

$SIG{HUP} = 'SIGHUP_handler';

my $poll = IO::Poll->new;

my $sock = new IO::Socket::INET(
   PeerAddr => "127.0.0.1",
   PeerPort => "12000",
   Proto => 'tcp') or die "Error creating socket: $!";

$poll->mask($sock, POLLIN);

while(1) {
   $pret = $poll->poll($poll_timeout);
   if ($pret == 0) {
      syswrite(STDOUT, "Timeout occured...\n");
   }
   elsif ($pret == -1) {
      syswrite(STDOUT, "Error occured: $!\n");
   }
   else {
      @ready = $poll->handles();

      foreach $handle (@ready) {
         $rret = sysread($handle, $readbuffer, 1024);
         if ($rret == 0) {
            syswrite(STDOUT, "No data to read on socket, exiting...\n");
            exit 1;
         }
         syswrite(STDOUT, "msg: $readbuffer");
      }
   }
}