I wanted to get time from an ntp server listening on port 123 of UDP rfc5905 . I found a solution here . Under my php working page:
<!doctype html> <?php session_start(); $please_wait = ''; $last = time(); if(isset($_SESSION['last'])) { $last = $_SESSION['last']; } else { $_SESSION['last'] = $last; } //wrap the whole thing in a test for the last hit-time on the page, to avoid abusing NTP servers if (time() - $last < 15) { $wait = time() - $last; $please_wait = 'Request limit exceeded, please wait ' . (15 - $wait) . ' s.'; $server = $vn_response = $mode_response = $stratum_response = $remote_originate = $remote_received = $remote_received = $remote_transmitted = $delay_ms = $ntp_time_formatted = $server_time_formatted = $please_wait; } else { $_SESSION['last'] = time(); $bit_max = 4294967296; $epoch_convert = 2208988800; $vn = 3; $servers = array('0.uk.pool.ntp.org','1.uk.pool.ntp.org','2.uk.pool.ntp.org','3.uk.pool.ntp.org'); $server_count = count($servers); //see rfc5905, page 20 //first byte //LI (leap indicator), a 2-bit integer. 00 for 'no warning' $header = '00'; //VN (version number), a 3-bit integer. 011 for version 3 $header .= sprintf('%03d',decbin($vn)); //Mode (association mode), a 3-bit integer. 011 for 'client' $header .= '011'; //echo bindec($header); //construct the packet header, byte 1 $request_packet = chr(bindec($header)); //we'll use a for loop to try additional servers should one fail to respond $i = 0; for($i; $i < $server_count; $i++) { $socket = @fsockopen('udp://'.$servers[$i], 123, $err_no, $err_str,1); if ($socket) { //add nulls to position 11 (the transmit timestamp, later to be returned as originate) //10 lots of 32 bits for ($j=1; $j<40; $j++) { $request_packet .= chr(0x0); } //the time our packet is sent from our server (returns a string in the form 'msec sec') $local_sent_explode = explode(' ',microtime()); $local_sent = $local_sent_explode[1] + $local_sent_explode[0]; //add 70 years to convert unix to ntp epoch $originate_seconds = $local_sent_explode[1] + $epoch_convert; //convert the float given by microtime to a fraction of 32 bits $originate_fractional = round($local_sent_explode[0] * $bit_max); //pad fractional seconds to 32-bit length $originate_fractional = sprintf('%010d',$originate_fractional); //pack to big endian binary string $packed_seconds = pack('N', $originate_seconds); $packed_fractional = pack("N", $originate_fractional); //add the packed transmit timestamp $request_packet .= $packed_seconds; $request_packet .= $packed_fractional; if (fwrite($socket, $request_packet)) { $data = NULL; stream_set_timeout($socket, 1); $response = fread($socket, 48); //the time the response was received $local_received = microtime(true); //echo 'response was: '.strlen($response).$response; } fclose($socket); if (strlen($response) == 48) { //the response was of the right length, assume it valid and break out of the loop break; } else { if ($i == $server_count-1) { //this was the last server on the list, so give up die('unable to establish a connection'); } } } else { if ($i == $server_count-1) { //this was the last server on the list, so give up die('unable to establish a connection'); } } } //unpack the response to unsiged lonng for calculations $unpack0 = unpack("N12", $response); //print_r($unpack0); //present as a decimal number $remote_originate_seconds = sprintf('%u', $unpack0[7])-$epoch_convert; $remote_received_seconds = sprintf('%u', $unpack0[9])-$epoch_convert; $remote_transmitted_seconds = sprintf('%u', $unpack0[11])-$epoch_convert; $remote_originate_fraction = sprintf('%u', $unpack0[8]) / $bit_max; $remote_received_fraction = sprintf('%u', $unpack0[10]) / $bit_max; $remote_transmitted_fraction = sprintf('%u', $unpack0[12]) / $bit_max; $remote_originate = $remote_originate_seconds + $remote_originate_fraction; $remote_received = $remote_received_seconds + $remote_received_fraction; $remote_transmitted = $remote_transmitted_seconds + $remote_transmitted_fraction; //unpack to ascii characters for the header response $unpack1 = unpack("C12", $response); //print_r($unpack1); //echo 'byte 1: ' . $unpack1[1] . ' | '; //the header response in binary (base 2) $header_response = base_convert($unpack1[1], 10, 2); //pad with zeros to 1 byte (8 bits) $header_response = sprintf('%08d',$header_response); //Mode (the last 3 bits of the first byte), converting to decimal for humans; $mode_response = bindec(substr($header_response, -3)); //VN $vn_response = bindec(substr($header_response, -6, 3)); //the header stratum response in binary (base 2) $stratum_response = base_convert($unpack1[2], 10, 2); $stratum_response = bindec($stratum_response); //echo 'stratum: ' . bindec($stratum_response); //calculations assume a symmetrical delay, fixed point would give more accuracy $delay = (($local_received - $local_sent) / 2) - ($remote_transmitted - $remote_received); $delay_ms = round($delay * 1000) . ' ms'; //echo 'delay: ' . $delay * 1000 . 'ms'; $server = $servers[$i]; $ntp_time = $remote_transmitted - $delay; $ntp_time_explode = explode('.',$ntp_time); $ntp_time_formatted = date('Ymd H:i:s', $ntp_time_explode[0]).'.'.$ntp_time_explode[1]; //compare with the current server time $server_time = microtime(); $server_time_explode = explode(' ', $server_time); $server_time_micro = round($server_time_explode[0],4); $server_time_formatted = date('Ymd H:i:s', time()) .'.'. substr($server_time_micro,2); } ?> <html lang="en"> <head> <meta charset="utf-8"> <title></title> <meta name="description" content=""> <meta name="author" content=""> <style type="text/css"> td{ width: 160px; height: 20px; padding: 4px; border: 1px solid #000; font-size: 12px; } .ntp_response{ width: 240px; } </style> </head> <body> <table border="0"> <tr> <td>Server: <td class="ntp_response"><?php echo $server;?></td> </tr> <tr> <td>VN (version number):</td> <td class="ntp_response"><?php echo $vn_response;?></td> </tr> <tr> <td>Mode:</td> <td class="ntp_response"><?php echo $mode_response;?></td> </tr> <tr> <td>Stratum:</td> <td class="ntp_response"><?php echo $stratum_response;?></td> </tr> <tr> <td>Origin time:</td> <td class="ntp_response"><?php echo $remote_originate;?></td> </tr> <td>Received:</td> <td class="ntp_response"><?php echo $remote_received;?></td> </tr> <td>Transmitted:</td> <td class="ntp_response"><?php echo $remote_transmitted;?></td> </tr> <td>Delay:</td> <td class="ntp_response"><?php echo $delay_ms;?></td> </tr> <td>NTP time:</td> <td class="ntp_response"><?php echo $ntp_time_explode[0];?></td> </tr> <td>Server time:</td> <td class="ntp_response"><?php echo $server_time_formatted;?></td> </tr> </table> </body> </html>