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從this page閱讀關於服務器發送的事件時，我對事件發生時間感到困惑。基本上，example shown有一個PHP腳本發送系統時間的網頁：3-4秒後收到服務器發送的事件
<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
$time = date('r');
echo "data: The server time is: {$time}\n\n";
flush();
?>
雖然頁面接收並對其進行渲染：
if(typeof(EventSource) !== "undefined") {
var source = new EventSource("demo_sse.php");
source.onmessage = function(event) {
document.getElementById("result").innerHTML += event.data + "<br>";
};
} else {
document.getElementById("result").innerHTML = "Sorry, your browser does not support server-sent events...";
}
我的困惑是，服務器似乎發送消息每3-4秒：
The server time is: Tue, 20 Sep 2016 11:55:12 -0400
The server time is: Tue, 20 Sep 2016 11:55:16 -0400
The server time is: Tue, 20 Sep 2016 11:55:20 -0400
The server time is: Tue, 20 Sep 2016 11:55:23 -0400
The server time is: Tue, 20 Sep 2016 11:55:28 -0400
The server time is: Tue, 20 Sep 2016 11:55:32 -0400
The server time is: Tue, 20 Sep 2016 11:55:35 -0400
The server time is: Tue, 20 Sep 2016 11:55:39 -0400
The server time is: Tue, 20 Sep 2016 11:55:43 -0400
The server time is: Tue, 20 Sep 2016 11:55:46 -0400
The server time is: Tue, 20 Sep 2016 11:55:50 -0400
The server time is: Tue, 20 Sep 2016 11:55:53 -0400
The server time is: Tue, 20 Sep 2016 11:55:57 -0400
The server time is: Tue, 20 Sep 2016 11:56:01 -0400
The server time is: Tue, 20 Sep 2016 11:56:04 -0400
The server time is: Tue, 20 Sep 2016 11:56:08 -0400
The server time is: Tue, 20 Sep 2016 11:56:12 -0400
The server time is: Tue, 20 Sep 2016 11:56:15 -0400
但是，我沒有看到這個延遲無論是在服務器端還是在客戶端。它是網站服務器和我的瀏覽器之間的網絡滯後嗎？或者是別的什麼？