comet基于http长连接的推送
比如web im 消息比轮询即时。减轻服务器压力。减少tcp三次握手的次数
<?php
/*
Simple COMET script tested to work with IE6, IE8, IE9, Chrome 5, Chrome 10, Firefox 3.6.16, Firefox 4, Safari 5, Opera 11
*/
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
//Turn of Apache output compression
// Necessary if you have gzip setup in your httpd.conf (e.g. LoadModule deflate_module modules/mod_deflate.so)
apache_setenv('no-gzip', 1);
ini_set('zlib.output_compression', 0);
//Disable all PHP output buffering
ini_set('output_buffering', 'Off');
ini_set('implicit_flush', 1);
ob_implicit_flush(1);
for ($i = 0, $level = ob_get_level(); $i < $level; $i++) { ob_end_flush(); } //Flush all levels of the buffer to start
error_reporting(E_ALL);
?><html>
<head>
<title>Comet php backend</title>
</head>
<body>
<script type="text/javascript">
var dumpText = window.parent.dumpText;
</script>
<?php
$startTime = time();
$maxLoopTime = 100;
while(time()-$startTime < $maxLoopTime) {
echo '<script type="text/javascript">';
echo "dumpText(".time().');'.str_repeat(' ',500); //500 characters of padding
echo "</script>\r\n";
flush();
$randSleep = mt_rand(100000, 2000000); //sleep between 100 ms and 2 seconds
usleep($randSleep);
}
?>
<script type="text/javascript">dumpText("Output Finished");location.reload();</script>
</body>
</html>
<html>
<head>
<title>Comet demo</title>
<style type="text/css">
.hiddenIframe {
position:absolute;
top:0px;
left:0px;
display:block;
z-index:-999;
visibility:hidden;
}
</style>
</head>
<body>
<p id="content">The server time will be shown here</p>
<script type="text/javascript">
var content = document.getElementById('content');
var dumpText = function(text){
content.innerHTML = content.innerHTML + '<BR>'+ text;
}
</script>
<iframe src="comnet.php"></iframe>
</body>
</html>
每个人都需要一台速度更快、更稳定的 PC。随着时间的推移，垃圾文件、旧注册表数据和不必要的后台进程会占用资源并降低性能。幸运的是，许多工具可以让 Windows 保持平稳运行。
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