php 实现监听服务器

<?php

header('content-type:text/html;charset=utf-8');

set_time_limit(0);

error_reporting(E_WARNING);

$radius=array(

    '106.187.93.138'=>array('url'=>'https://manager.linode.com/linodes/dashboard/TXVPN_Pro_Radius','urlbefore'=>'https://manager.linode.com/session/index?r=/linodes/dashboard/TXVPN_Pro_Radius'),

    );

function pings($ip,$time) {    exec('ping -n 1 -w '.$time.' '.$ip,$list);    $errorlog=$list[2];    $encode = mb_detect_encoding($errorlog, array("ASCII",'UTF-8',"GB2312","GBK",'BIG5'));      //echo $encode;    $str_encode = mb_convert_encoding($errorlog, 'UTF-8', $encode);     /*echo $str_encode;*/    if('请求超时。' === $str_encode){        return $ip;    }else{        return false;    }}