Description:
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stream_get_contents() with any maxlength greater than -1 returns an empty string,
This only appears to occur with UDP streams opened via stream_socket_client(), specifically on Windows 10.

This problem doesn't occur on Linux and may function fine on older versions of Windows.


The problem appears to reside somewhere in the php_stream_eof call within _php_stream_copy_to_mem - php_stream_eof seems to always return true on UDP streams on Windows 10 systems. More digging required.

Test script:
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//Submit DNS Request
$data = base64_decode("1oIBAAABAAAAAAAAB2V4YW1wbGUDb3JnAAABAAE=");
$fd = stream_socket_client("udp://8.8.8.8:53", $errno, $errstr, 0, STREAM_CLIENT_CONNECT | STREAM_CLIENT_ASYNC_CONNECT);
stream_set_blocking($fd, 0);
stream_socket_sendto($fd,$data);
sleep(1);
var_dump(stream_get_contents($fd,65565)); //Does not work
var_dump(stream_get_contents($fd));       //No maxlength, works fine
stream_socket_shutdown($fd,STREAM_SHUT_RDWR);

Expected result:
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Returns a valid DNS response roughly 45 bytes long, then an empty string.

string(45) "<>"
string(0) ""

Actual result:
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Returns an empty string, then a valid DNS response.

string(0) ""
string(45) "<>"