我想php继续监听socket（php socket编程）

I have a device which sends data in every 5 seconds using tcp and i am using php socket programming

and my code isn't working this code print nothing and when i use this code without loop(while loop) then it works i want to continue listen the data that my client sends in every 5 seconds please help me out....thanks in advance.

    <?php
error_reporting(E_ALL);
set_time_limit (0);

$host = '103.21.XX.XX';

$port = 60000;
$con = 1;
$word = "";

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP) or die(socket_strerror(socket_last_error()));
$result = socket_bind($socket, $host, $port) or die(socket_strerror(socket_last_error($socket))); 

$result = socket_listen($socket) or die(socket_strerror(socket_last_error($socket)));

while ($con==1) {
    # code...

   $spawn = socket_accept($socket) or die("Could not accept incoming connection
");
    $input = socket_read($spawn, 2048) or die("Could not read input
");
     $input=(String)$input;
echo $input;
    if ($input == 'exit') 
    {
        $close = socket_close($sock);
        $con = 0;
    }

    if($con == 1)
    {
        $word .= $input;
    }
}

echo $word;

?>