Sending binary files blocks browser

tanis

I've got a script that is behaving in a wild way.

There's a page that opens a popup.
In the popup there's a link to a PHP script that sends a file to the user by reading the content of the file and sending it over to the browser.
Download works fine.
But while the download is going on, the window that opened the popup and the popup too are no longer useable. I mean. You can gain focus on them and write a new address in the URL, but whatever page you try to open the browser goes in error.

It's the first time I see this behaviour. I think this has something to do with the download script since it only happens when I download a file through it. Any suggestions?

su1d

Are you testing that all on the same box?
Is the file big enough?
Probably, your script blocks everything on the box including browser.
This could depend on a way you pass a file to a user.
I'd recommend something like this:

fpassthru(fopen('file.bin', 'rb'));

there's no need to call fclose() in this code because fpassthru() automatically closes the file after it content has been passed to the output.

tanis

I'm running tests on different boxes but all behave the same way.
The files I'm using are way big (around a gig in size) and are not on the same LAN, so I've got plenty of time to do whatever test I need 🙂

I'm doing something different than using fpassthru() because I need to do some checks and write a row in a db every once in a while while sending the file. So my script looks more like:

header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=" . $l["nomefile"] . "; size=" . $l["dimensione"]);
header("Content-Length: " . $l["dimensione"]);


// Download can take a while... no max time limit 
set_time_limit(0); 

$fp = fopen($l["path"] . "/" . $l["nomefile"], "rb");
$bread=0;
$lastperc = 0;
$lastrun = time();
while (!feof($fp)) {
	$buf = fread($fp, 1024);
	$bread += 1024;
	echo $buf;
	$perc = floor(($bread/$l["dimensione"])*100);
	if ( (($perc % 10) == 0) && ($perc != $lastperc)) {
		$lastperc=$perc;
		//echo "perc: $perc / $bread / " . $l["dimensione"] . "<br>";
		$sql = "update sessioni_scrocco set percentuale = " . $perc . " where " .
		"(hash = '" . $HTTP_GET_VARS["hash_coda"] . "') and " .
		"(id_utente = '" . $HTTP_SESSION_VARS["multiplayer_userid"] . "')";
		$q = mysql_db_query("tanis", $sql, $hu);
	}

$thisrun = time();
//Aggiorna la riga ogni 2 secondi
if ( ($thisrun - $lastrun) > 2 ) {
	$lastrun = $thisrun;
	$sql = "update sessioni_scrocco set ultimogiro = '" . $lastrun . "' where " .
	"(hash = '" . $HTTP_GET_VARS["hash_coda"] . "') and " .
	"(id_utente = '" . $HTTP_SESSION_VARS["multiplayer_userid"] . "')";
	$q = mysql_db_query("tanis", $sql, $hu);
}
}
fclose($fp);

su1d

Reading a gig file 1K by 1K and UPDATE'ing a table everytime you read a 1K is not a very good idea.
Look, you have to touch the DB 1 million times before the download is done. If I were your poor MySQL server, I'd kicked your ass. =)
Try fread($fp, 1024 * 64) or even more...
And update the DB at least every 1-5Mb.

tanis

Have a better look at the code. It updates only at every 10% of increment in the transfer, thus leading to 10 updates per file whatever the size is 🙂

Anyway the files that are going to be sent over are gonna be smaller 😉

tanis

I've not yet found a solution to this issue.
It seems like that until the PHP script has finished processing the page (and thus echoing the downloaded file to the browser) the browser is blocked.