TestEvent.pl
sudo kill -USR1 $(cat events.pid)
SktClnt.pl
Enter data to send:
A.B.C
sudo kill -HUP $(cat events.pid)

##</code><code>##

25-04-2020 18:03:46, Port: 55129
looping 0
25-04-2020 18:04:02, User 1 signal received
25-04-2020 18:04:11, Connection received from 192.168.0.153
Data: A.B.C
loop data: A.B.C
25-04-2020 18:04:20, Hangup

##</code><code>##

#!/usr/bin/perl

# EventsTest.pl
# Version 1.0, 25 April 2020

use Sys::HostIP;
use Daemon::Daemonize qw( :all );
use IO::Socket::INET;
use Event;
use AnyEvent;
use Date::Calc qw( Today_and_Now );

use strict;
use warnings;

$|++;

# ********************************************************** #
# ************** Variables to be set by user *************** #
# ********************************************************** 
  # base path/name for log files (e.g. /home/anita2r/events.log)
  my $base = "/home/anita2R/events";
  # port for socket connection
  my $port = 55129;

# ********************************************************** #
# ****************** Create log files etc. ***************** #
# ********************************************************** #
# Setup log, error and pid files
  my $error_log = "$base.err";
  my $pid_file  = "$base.pid";
  my $msg_log   = "$base.log";
# clear error and log files
  truncate $error_log, 0;
  truncate $msg_log,   0;

# ********************************************************** #
# ************* Create a communications socket ************* #
# ********************************************************** #
# create a socket and log port number
  my $hostip = Sys::HostIP->new;
  my $ip = $hostip->ip;
  # save port to log file
  my $DtTm = DtTmStmp();
  open( my $fh, '>>', $msg_log );
      print $fh "$DtTm, Port: $port\n";
  close $fh;

# setup socket
  my $skt = IO::Socket::INET->new(
               Listen    => 1,
               LocalAddr => $ip,
               LocalPort => $port,
               Proto     => 'tcp',
               Reuse     => 1,
               )
        or die "$! ... Can't open socket on port $port\n";

# ********************************************************** #
# ******************** Signal handlers ********************* #
# ********************************************************** #

# ********************************************************** #
# HUP signal handler
# for this test HUP will log and close the script
my $wtforhup = AnyEvent->signal( signal => "HUP",
                                 cb     => sub {
    my $DtTm = DtTmStmp();
    open( my $fh, '>>', $msg_log );
        print $fh "$DtTm, Hangup\n";
    close $fh;

    # clear the pid file and stop the daemon
    delete_pidfile( $pid_file );
    exit 1;
    }
    );

# ********************************************************** #
# USR1 signal handler
# for this test USR1 will just add an entry to the log
my $wtforusr1 = AnyEvent->signal( signal => "USR1",
                                  cb     => sub{
    my $DtTm = DtTmStmp();
    open( my $fh, '>>', $msg_log );
        print $fh "$DtTm, User 1 signal received\n";
    close $fh;
    }
    );

# ********************************************************** #
# IO socket handler
# read data, log receive
#  and pass it on for additional processing
my $data;
my $iocv    = AnyEvent->condvar;
my $wtforio = AnyEvent->io( fh     => \*$skt,
                            poll   => 'r',
                            cb     => sub{
    my $lskt = $skt->accept();

    while( <$lskt> ) {
        $data = $_;
        chomp $data;
        my $hostip = $lskt->peerhost();
        # log received data
        my $DtTm = DtTmStmp();
        open( my $fh, '>>', $msg_log );
            print $fh "$DtTm, Connection received from $hostip\n";
            print $fh "Data: $data\n";
        close $fh;
    }
    close( $lskt );

    # send data for further processing
    #  $iocv->recv is in main loop
    $iocv->send( $data );
    }
    );

# ********************************************************** #
# *********************** Daemonize ************************ #
# ********************************************************** #

# daemonize, redirect errors & save new pid
  daemonize(
            close  => 'std',
            stderr => $error_log,
           );

  write_pidfile( $pid_file );

# ********************************************************** #
# ********************* Initialization ********************* #
# ********************************************************** #

# In the real program, various initialization routines
#  are carried out before entering the main program loop

# ********************************************************** #
# ******************* Main Program Loop ******************** #
# ********************************************************** #

my $loop = 1;
my $a = 0;
while( $loop ) {

    # just to show whether the loop is running
    # one entry every 5 seconds
    if( $a % 5 == 0) {
    open( $fh, '>>', $msg_log );
        print $fh "looping $a\n";
    close $fh;
    }
    $a++;
    sleep 1;

    # $iocv-recv blocks until an $iorecv->send
    my $data = $iocv->recv;
    open( $fh, '>>', $msg_log );
        print $fh "loop data: $data\n";
    close $fh;
    # done with this cv
    undef $iocv;

    # setup a fresh cv - loop will be blocked until next send
    $iocv = AnyEvent->condvar;
}
exit 0;

# ********************************************************** #
# ****************** General subroutines ******************* #
# ********************************************************** #

# ********************************************************** #
# date/time stamp
sub DtTmStmp {

    my( $yr, $mo, $dy, $hr, $mi, $se ) = Today_and_Now();
    my $DtTm = sprintf( "%02d-%02d-%04d %02d:%02d:%02d",
                                       $dy, $mo, $yr, $hr, $mi, $se );
    return $DtTm;
}

# ********************************************************** #