html5中的server-sent event服务器推送，不是说不同与轮询的推送机制吗？
为什么还是客户端每秒发起请求呢？
正所谓“推送”，服务器应该是主动的啊，而不是客户端主动请求。
下面是我在控制台看到的情况，客户端每秒发起请求的：
即使服务端没有数据也会每秒都有请求：
客户端代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>EventSource</title>
<script type="text/javascript">
onload=function(){
source=new EventSource("eventsource.php");
source.onmessage=function(event){
console.log(event);
};
/*source.onopen=function(e){
console.log(e);
}*/
/*source.onerror=function(e){
console.log(e);
}*/
source.addEventListener('myevent', function(e) {
document.write(e.data+"<br>");
console.log(e.data);
});
}
</script>
</head>
<body>
</body>
</html>服务端代码：
<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
date_default_timezone_set('PRC');//中国
$time = date('r');
session_start();
$arr=[
'name'=>'lanyue',
'age'=>21,
'time'=>$time,
'session'=>session_id()
];
$json=json_encode($arr);
//echo "data: {$json}";
echo "event: myevent\r\n";
echo "data: {$json}\r\n";
echo "id: 101\r\n";
echo "\n\n";//必须以这个结束
ob_flush();
flush();
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
Ask the client how to write the code. Now it is obvious that the client has been requesting.
Please refer to the link description I answered before