PHP swoole 监听端口进程

<?php 
class ListeningPort{
    const PORT=9601;
    public function port()
    {
        $shell = "netstat -anp | grep ". self::PORT . " | grep LISTEN | wc -l";
        $res = shell_exec($shell);
        if($res != 1){
            echo date("Y-m-d H:i:s") ." error ".PHP_EOL;
        }else{
            echo date("Y-m-d H:i:s") ." success ".PHP_EOL;
        }
    }
}
swoole_timer_tick(2000,function($timer_id){
    echo "执行了";
    (new ListeningPort())->port();
});

nohup php listeningPort.php > 1.txt