SimpleComet是一个轻量级的comet的封装类, 能智能的识别浏览器,应用不同的comet技术,在firefox浏览器上使用ajax，在IE、opera浏览器上使用htmlfile,iframe.

<script type="text/javascript"> // This function will be called every time the server pushes a new event. function push(event) {  // For this example, we simply show the excuse on the page.   document.getElementById('excuse').innerHTML = event; }   // This function will be called when/if the stream closes. function disconnected() {   // For this example we'll just show a nice message.   document.getElementById('excuse').innerHTML = '<img src="img/arrow.png" alt="" title="" />'+    ' Click to see MORE reasons why this souldn\'t work!';  document.getElementById('control').value = 'start'; }   // This function is executed when the button is clicked. function toggle() {  // First we check if the stream is open.  if (!comet.active) {    // Lets start streaming!    comet.open('excuses.php', push, disconnected);    document.getElementById('control').value = 'stop';  } else {    // Streaming is active, means the user wants to stop it.    comet.close();  } } </script>


<!--?php   // First we load the SimpleComet PHP class and the list of excuses. require('inc/simplecomet.class.php'); $comet = new SimpleComet(); $excuses = file('inc/excuses.txt');   // This is an infinite loop, which makes the stream endless. while (true) {  // We fetch an excuse at random.  $excuse = trim($excuses[rand(0, count($excuses))]);   // If the excuse is too long, we get another one.   if (strlen($excuse) --> 60) { continue; }   // Finally, we push our excuse to the client.   $comet->push($excuse);  // 5 seconds delay before the next excuse.  sleep(5); }   ?>

simplecomet能监听出链接是否已经断了,是不是很智能，只要负责服务端的输出就行.