Uses XMLHttpRequest:
"server push" (using XMLHTTPRequest Interactive state for Firefox/Webkit, XDomainRequest for IE) "long polling" or "polling" logic for old browsers
Browser Support:
IE6+, Firefox, Chrome, Opera, Safari
Advantages:
- Simple server-side code
- Based on last specification of EventSource
- "server push" for IE 8+, Firefox 3.5+, Chrome 7+, Safari 5+, Opera 11+
- Polyfill is independent from document methods (addEventListener), so you can use it in a Web Worker's
- cross-domain requests supported for IE 8+, Firefox 3.5+, Chrome 7+, Safari 5+
Server-side requirements:
When "server push" not supported, "X-Requested-With" HTTP Header is sended on each request to tell your server side script to close connection after sending a data. XDomainRequest sends "Last-Event-ID" with POST body (XDomainRequest object does not have a setRequestHeader method) Also XDomainRequest requires send two kilobyte padding at the top of the response stream. ( http://blogs.msdn.com/b/ieinternals/archive/2010/04/06/comet-streaming-in-internet-explorer-with-xmlhttprequest-and-xdomainrequest.aspx?PageIndex=1 )
Other EventSource polyfills:
- https://github.com/remy/polyfills/blob/master/EventSource.js by Remy Sharp
- https://github.com/rwldrn/jquery.eventsource by rick waldron
CORS in native SSE (not implemented yet):
varhttp=require('http');varfs=require('fs');http.createServer(function(req,res){vart=null;if(req.url.indexOf('/events')===0){res.writeHead(200,{'Content-Type': 'text/event-stream','Cache-Control': 'no-cache','Connection': 'keep-alive',//'Access-Control-Allow-Credentials': 'true','Access-Control-Allow-Origin': req.headers.origin});res.write(':'+Array(2049).join(' ')+'\n');//2kb padding for IEres.write('data: '+Date()+'\n\n');t=setInterval(function(){res.write('data: '+Date()+'\n\n');},1000);res.socket.on('close',function(){clearInterval(t);});if(req.headers['x-requested-with']){res.end();}}else{if(req.url==='/index.html'||req.url==='/eventsource.js'){res.writeHead(200,{'Content-Type': req.url==='/index.html' ? 'text/html' : 'text/javascript'});res.write(fs.readFileSync(__dirname+req.url));}res.end();}}).listen(8081);//! port :8081<?header('Access-Control-Allow-Origin: ' . @$_SERVER['HTTP_ORIGIN']);
//header('Access-Control-Allow-Credentials: true');header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
// prevent bufferring
@apache_setenv('no-gzip', 1);
@ini_set('zlib.output_compression', 0);
@ini_set('implicit_flush', 1);
for ($i = 0; $i < ob_get_level(); $i++) { ob_end_flush(); }
ob_implicit_flush(1);
// getting last-event-id from POST or from http headers$postData = @file_get_contents('php://input');
if (preg_match('#Last\\-Event\\-ID\\=([\\s\\S]+)#ui', @$postData, $tmp)) {
$lastEventId = urldecode(@$tmp[1]);
} else {
$lastEventId = @$_SERVER["HTTP_LAST_EVENT_ID"];
}
// 2kb padding for IEecho':' . str_repeat('', 2048) . "\n";
// event-streamfor ($i = intval($lastEventId) + 1; $i < 100; $i++) {
echo"id: $i\n";
echo"data: $i;\n\n";
sleep(1);
}
?><!DOCTYPE html><html><head><metacharset="utf-8" /><title>EventSource example</title><metahttp-equiv="X-UA-Compatible" content="IE=edge"><scriptsrc="../eventsource.js"></script><script>vares=newEventSource('events.php');es.addEventListener('open',function(event){vardiv=document.createElement('div');div.innerHTML='opened: '+es.url;document.body.appendChild(div);},false);es.addEventListener('message',function(event){document.body.appendChild(document.createTextNode(event.data));},false);es.addEventListener('error',function(event){vardiv=document.createElement('div');div.innerHTML='closed';document.body.appendChild(div);},false);</script></head><body></body></html>