EventSource polyfill - http://www.w3.org/TR/eventsource/
Browser support:
- IE 8+, Firefox 3.5+, Chrome 3+, Safari 4+, Opera 12+
- It works on Mobile Safari, Opera Mobile, Chrome for Android, Firefox for Android
- It does not work on: Android Browser(requires 4 KB padding), Opera Mini
Advantages:
- Simple server-side code
- Cross-domain requests support ("withCredentials" is not supported in IE8-IE9)
Server-side requirements:
- "Last-Event-ID" is sent in a query string (CORS + "Last-Event-ID" header is not supported by all browsers)
- It is required to send 2 KB padding for IE < 10 and Chrome < 13 at the top of the response stream
- You need to send "comment" messages each 15-30 seconds, this messages will be used as heartbeat to detect disconnects - see https://bugzilla.mozilla.org/show_bug.cgi?id=444328
Specification:
Other EventSource polyfills:
- https://github.com/remy/polyfills/blob/master/EventSource.js by Remy Sharp
- https://github.com/rwldrn/jquery.eventsource by rick waldron
EXAMPLE
server-side (node.js)
var PORT = 8081;
var http = require("http");
var fs = require("fs");
var url = require("url");
http.createServer(function (request, response) {
var parsedURL = url.parse(request.url, true);
var pathname = parsedURL.pathname;
if (pathname === "/events.php") {
response.writeHead(200, {
"Content-Type": "text/event-stream",
"Cache-Control": "no-cache",
"Access-Control-Allow-Origin": "*"
});
response.write(":" + Array(2049).join(" ") + "\n"); // 2kB padding for IE
response.write("retry: 2000\n");
var lastEventId = Number(request.headers["last-event-id"]) || Number(parsedURL.query.lastEventId) || 0;
var timeoutId = 0;
var i = lastEventId;
var c = i + 100;
var f = function () {
if (++i < c) {
response.write("id: " + i + "\n");
response.write("data: " + i + "\n\n");
timeoutId = setTimeout(f, 1000);
} else {
response.end();
}
};
f();
response.on("close", function () {
clearTimeout(timeoutId);
});
} else {
if (pathname === "/") {
pathname = "/index.html";
}
if (pathname === "/index.html" || pathname === "../eventsource.js") {
response.writeHead(200, {
"Content-Type": pathname === "/index.html" ? "text/html" : "text/javascript"
});
response.write(fs.readFileSync(__dirname + pathname));
}
response.end();
}
}).listen(PORT);or use PHP (see php/events.php)
<?php
header("Content-Type: text/event-stream");
header("Cache-Control: no-cache");
header("Access-Control-Allow-Origin: *");
$lastEventId = floatval(isset($_SERVER["HTTP_LAST_EVENT_ID"]) ? $_SERVER["HTTP_LAST_EVENT_ID"] : 0);
if ($lastEventId == 0) {
$lastEventId = floatval(isset($_GET["lastEventId"]) ? $_GET["lastEventId"] : 0);
}
echo ":" . str_repeat(" ", 2048) . "\n"; // 2 kB padding for IE
echo "retry: 2000\n";
// event-stream
$i = $lastEventId;
$c = $i + 100;
while (++$i < $c) {
echo "id: " . $i . "\n";
echo "data: " . $i . ";\n\n";
ob_flush();
flush();
sleep(1);
}
?>index.html (php/index.html):
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>EventSource example</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<script src="../eventsource.js"></script>
<script>
var es = new EventSource("events.php");
var listener = function (event) {
var div = document.createElement("div");
var type = event.type;
div.appendChild(document.createTextNode(type + ": " + (type === "message" ? event.data : es.url)));
document.body.appendChild(div);
};
es.addEventListener("open", listener);
es.addEventListener("message", listener);
es.addEventListener("error", listener);
</script>
</head>
<body>
</body>
</html>License
The MIT License (MIT)
Copyright (c) 2012 [email protected]
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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