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POHTML5 Server-Sent Events prototyping - ambiguous error and repeated polling?
 

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    <p>I'm trying to get to grips with Server-Side Events as they fit my requirements perfectly and seem like they should be simple to implement, however I can't get past a vague error and what looks like the connection repeatedly being closed and re-opened. Everything I have tried is based on <a href="http://www.html5rocks.com/en/tutorials/eventsource/basics" rel="noreferrer">this</a> and other tutorials.</p> <p>The PHP is a single script:</p> <pre><code>&lt;?php header('Content-Type: text/event-stream'); header('Cache-Control: no-cache'); function sendMsg($id, $msg) { echo "id: $id" . PHP_EOL; echo "data: $msg" . PHP_EOL; echo PHP_EOL; ob_flush(); flush(); } $serverTime = time(); sendMsg($serverTime, 'server time: ' . date("h:i:s", time())); ?&gt; </code></pre> <p>and the JavaScript looks like this (run on body load):</p> <pre><code>function init() { var source; if (!!window.EventSource) { source = new EventSource('events.php'); source.addEventListener('message', function(e) { document.getElementById('output').innerHTML += e.data + '&lt;br /&gt;'; }, false); source.addEventListener('open', function(e) { document.getElementById('output').innerHTML += 'connection opened&lt;br /&gt;'; }, false); source.addEventListener('error', function(e) { document.getElementById('output').innerHTML += 'error&lt;br /&gt;'; }, false); } else { alert("Browser doesn't support Server-Sent Events"); } } </code></pre> <p>I have searched around a bit but can't find information on</p> <ol> <li>If Apache needs any special configuration to support server-sent events, and </li> <li>How I can initiate a push from the server with this kind of setup (e.g. can I simply execute the PHP script from CLI to give a push to the already-connected-browser?)</li> </ol> <p>If I run this JS in Chrome (16.0.912.77) it opens the connection, receives the time, then errors (with no useful information in the error object), then reconnects in 3 seconds and goes through the same process. In Firefox (10.0) I get the same behaviour.</p> <p><strong>EDIT 1</strong>: I thought the issue could be related to the server I was using, so I tested on a vanilla XAMPP install and the same error comes up. Should a basic server configuration be able to handle this without modification / extra configuration?</p> <p><strong>EDIT 2</strong>: The following is an example of output from the browser:</p> <pre><code>connection opened server time: 01:47:20 error connection opened server time: 01:47:23 error connection opened server time: 01:47:26 error </code></pre> <p>Can anyone tell me where this is going wrong? The tutorials I have seen make it look like SSE is very straightforward. Also any answers to my two numbered questions above would be really helpful.</p> <p>Thanks.</p>
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    1. COcan you post your timed loop, the code provided is error free. Do you drop the EventSource object at any time?
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    2. CO@tnt I won't be able to post the code until Monday, but there is no timed loop - default EventSource behaviour is to reconnect 3 seconds after the connection is lost. A single function (init(), above) is called once on body load which creates the connection, then the browser enters its connect-error-reconnect cycle all by itself.
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    3. COFrom W3C : Legacy proxy servers are known to, in certain cases, drop HTTP connections after a short timeout. To protect against such proxy servers, authors can include a comment line (one starting with a ':' character) every 15 seconds or so.
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