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UDP error package problem_PHP tutorial

Jul 14, 2016 am 10:07 AM
arrayconfudpwordundercodeoflookquestion

问题

看下面一段代码
$word = 'HELLO';
$conf = array(
array('ip'=>'10.1.146.133', 'port'=>2001),
array('ip'=>'10.1.146.133', 'port'=>2002)
);
function udpGet($word, $ip, $port)
{
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_set_option($sock, SOL_SOCKET, SO_SNDTIMEO, array('sec'=>2, 'usec'=>0));
socket_set_option($sock, SOL_SOCKET, SO_RCVTIMEO, array('sec'=>2, 'usec'=>0));
 
socket_sendto($sock, $word, strlen($word), 0x100, $ip, $port);
socket_recvfrom($sock, $result, 8192, 0, $host, $port);
 
socket_close($sock);
 
return $result;
}
 
for ($i=0; $i
{
$res = udpGet($word, $conf[$i]['ip'], $conf[$i]['port']);
var_dump($res);
}
就是连续用UPD向两个server收发数据(为说明问题,这里的server使用了最简单的回射逻辑),
如果一切流程正常,客户端会收到两次‘HELLO’。但是,如果服务端出了问题呢?
目前,客户端的超时时间是2秒,假设2001端口过了3秒发数据,而2002端口无法服务,
猜下结果会是什么呢?“两个NULL!”,直觉上应该是这个答案。如果你也这么认为,
那么恭喜你,答错了。
实际的答案是:
NULL
string(5) "HELLO"
分析
使用tcpdump抓包,得到如下结果
(133为服务端,163为客户端,客户端php版本5.3.1,Linux内核2.6.16)
12:01:39.014658 IP 10.1.146.163.40678 > 10.1.146.133.2001: UDP, length 5
12:01:41.015121 IP 10.1.146.163.40678 > 10.1.146.133.2002: UDP, length 5
12:01:42.016103 IP 10.1.146.133.2001 > 10.1.146.163.40678: UDP, length 5
 
按我的想法,两个请求应该使用不同的临时端口收发,但从抓包结果看,
客户端虽然进行了两次socket_create,但实际中却使用了同一临时端口(40678)
收发数据!这就使得第二个请求收到了第一个请求的回包。
 
感觉上这应该算是个系统的BUG,从实验中发现,此问题只在部分系统中存在,
比如Linux内核2.6.32+php5.2.3就没有此问题。
解决
每次指定socket端口,进行收发。如下面的红色代码所示。
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
$sendPort = rand(10240, 60000);
socket_bind($sock, ’10.1.146.163′, $sendPort);
socket_set_option($sock, SOL_SOCKET, SO_SNDTIMEO, array(‘sec’=>2, ‘usec’=>0));
socket_set_option($sock, SOL_SOCKET, SO_RCVTIMEO, array(‘sec’=>2, ‘usec’=>0));
当然,rand的端口也有可能出现对撞,但毕竟这种机率不大,可以从很大程度上解决问题。
如果有更好的解决办法,欢迎大家交流~
 
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www.bkjia.comtruehttp://www.bkjia.com/PHPjc/477851.htmlTechArticle问题 看下面一段代码 $word = HELLO; $conf = array( array(ip=10.1.146.133, port=2001), array(ip=10.1.146.133, port=2002) ); function udpGet($word, $ip, $port) { $sock = socke...
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