function gethostbyaddr_timeout($ip, $dns, $timeout = 1000)
{
// random transaction number (for routers etc to get the reply back)
$data = rand(0, 99);
// trim it to 2 bytes
$data = substr($data, 0, 2);
// request header
$data .= "\1\0\0\1\0\0\0\0\0\0";
// split IP up
$bits = explode(".", $ip);
// error checking
if (count($bits) != 4) return "ERROR";
// there is probably a better way to do this bit...
// loop through each segment
for ($x=3; $x>=0; $x--)
{
// needs a byte to indicate the length of each segment of the request
switch (strlen($bits[$x]))
{
case 1: // 1 byte long segment
$data .= "\1"; break;
case 2: // 2 byte long segment
$data .= "\2"; break;
case 3: // 3 byte long segment
$data .= "\3"; break;
default: // segment is too big, invalid IP
return "INVALID";
}
// and the segment itself
$data .= $bits[$x];
}
// and the final bit of the request
$data .= "\7in-addr\4arpa\0\0\x0C\0\1";
// create UDP socket
$handle = @fsockopen("udp://$dns", 53);
// send our request (and store request size so we can cheat later)
$requestsize = @fwrite($handle, $data);
@socket_set_timeout($handle, $timeout - $timeout%1000, $timeout%1000);
// hope we get a reply
$response = @fread($handle, 1000);
@fclose($handle);
if ($response == "")
return $ip;
// find the response type
$type = @unpack("s", substr($response, $requestsize+2));
if ($type[1] == 0x0C00) // answer
{
// set up our variables
$host = "";
$len = 0;
// set our pointer at the beginning of the hostname
// uses the request size from earlier rather than work it out
$position = $requestsize+12;
// reconstruct hostname
do
{
// get segment size
$len = unpack("c", substr($response, $position));
// null terminated string, so length 0 = finished
if ($len[1] == 0)
// return the hostname, without the trailing .
return substr($host, 0, strlen($host) -1);
// add segment to our host
$host .= substr($response, $position+1, $len[1]) . ".";
// move pointer on to the next segment
$position += $len[1] + 1;
}
while ($len != 0);
// error - return the hostname we constructed (without the . on the end)
return $ip;
}
return $ip;
}
Is probably a quicker way to do it at socket level if you have fsockopen or sockets enabled.
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