Dear huck.
Currently I have only one connection.(I expect to have more in the future).
I need to request device params and keep this connection for 5min (as polling time) and then release it.
Device will reconnect inmediatly after closing tcp socket.
This single connection is crashing my service.
Im traying to apply all concepts you mentioned but it is really hard for me , besides , the code you provided is not working.
Any way ; this my new version with my own eval blocks:

#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket::INET;
use threads;
use Net::MQTT::Simple;
use POSIX qw(strftime);
use Sys::Syslog qw(:DEFAULT :standard :macros);


my $mqtt;
my $client;
my $ident='tcp-mqtt_server';
my $logopt='ndelay';
my $facility='LOG_USER';
my $th_id;
my $topic;
my $value;


sub Main
{

    $mqtt = Net::MQTT::Simple->new("localhost:1883");


        openlog($ident, $logopt, $facility);    # don't forget this

    # flush after every write
    $| = 1;

    my ( $socket, $client_socket );
    
    # Bind to listening address and port
    $socket = new IO::Socket::INET (
        LocalHost => '0.0.0.0',
        LocalPort => '1001',
        Proto => 'tcp',
        Listen => 5,
        Reuse => 1
    ) or die "Could not open socket: ".$!."\n";

    print "SERVER Waiting for client connections...\n";
        syslog(LOG_INFO,"tcp-mqtt server starting");    

    my @clients = ();
    while(1)
    {
        # Waiting for new client connection.
        $client_socket = $socket->accept();
        # Push new client connection to it's own thread
        push ( @clients, threads->create( \&clientHandler, $client_soc
+ket ) );
        foreach ( @clients ) 
        {
            if( $_->is_joinable() ) {
                $_->join();
            }
        }
    }
    $socket->close();
    return 1;
}

sub clientHandler
{

    my ($client_socket) = @_;
    my %user = ();
        $user{peer_address} = $client_socket->peerhost();
    $user{peer_port} = $client_socket->peerport();
    $user{local_port} = $client_socket->sockport();
    $th_id = threads->tid();

    print "Client ".$user{peer_address}.":".$user{peer_port}.":".$user
+{local_port}."\n";
       syslog(LOG_INFO,"Client $user{peer_address}:$user{peer_port}:$u
+ser{local_port}:$th_id is connected");    

    eval{

            my $datestring = strftime "%a %b %e %H:%M:%S %Y", localtim
+e;
            printf("$datestring\n");
            
            print $client_socket "\n";
            print $client_socket "VLIN\n";


            while( my $buffer = <$client_socket> )
            {

                print $buffer;
                my $value = substr $buffer, 0,-2;
                $mqtt->retain("minimon/VLIN" => $buffer);
                   syslog(LOG_INFO,"VLIN: $buffer");    
                last;
                
            }

            sleep(300);

    };

    if($@){
           syslog(LOG_INFO,"tcp-mqtt exception:$@->getErrorMessage()")
+;    
    }

    $client_socket->shutdown(2);
    #$client_socket->close();
    print "Client exit from ".$user{peer_address}.":".$user{peer_port}
+."\n";
    # Client has exited so thread should exit too
    threads->exit();

}

# Start the Main loop
Main();
[download]

Thanks again for your words.

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