msqp.php

<?php

/*

Version history

1     - Initial release.
2     - Added option to use the official domain name instead of IPs and retry if
        a timeout occurs.
2.1   - Added more master servers.
2.1.1 - Fixed a bug, program didn't terminate if all master servers time out.
2.1.2 - Removed a now redundant variable.
2.2   - Seeding for long server lists.
      - Removed the domain name because it's often better to try different
        servers.
2.2.1 - Bug fix: Timeout showed wrong master server IP.
      - Bug fix: Check whether the new seed starts with a duplicate or not.
      - Bug fix: Don't close socket twice.
2.3   - Retry queries on timeout if the first query was successful.
2.3.1 - Reading the whole address again if it starts with a zero.
      - Increased timeout to avoid a communication issue.
      - Removed maximum number of timeouts for testing.
2.4   - Again using hl1master.steampowered.com because IPs change often.
      - Endless retries because this server often times out.
2.5   - Trying following ports on timeout or if the response wasn't correct.
2.5.3 - Cosmetic changes (defines, variable name).
2.5.4 - Code optimisation.
2.6   - Repeat until list isn't empty.
*/

// Currently uses ports 27011-27013 and 27015.
$master_servers = array("hl2master.steampowered.com");

define("MIN_PORT", 27011); // Range of port numbers which the master servers
define("MAX_PORT", 27015); // potentially use.
define("FILTER", '\gamedir\tfc'); // game = Team Fortress Classic
define("REGION", "\xFF"); // region = world
define("TIMEOUT", 2.0); // 2s timeout

function query_timeout($socket, $seed)
{
   echo "Sending query to master server.\n";
   stream_set_timeout($socket, TIMEOUT);
   if (!fwrite($socket, "1".REGION."$seed\0".FILTER."\0"))
   {
      fclose($socket);
      exit("fwrite error\n");
   }

   echo "Reading response header.\n";
   stream_set_timeout($socket, TIMEOUT);
   $s = bin2hex(fread($socket, 6));
   $info = stream_get_meta_data($socket);
   if ($info['timed_out'])
      echo "Master server timed out.\n";
   else
   {
      if ($s !== "ffffffff660a")
      {
         fclose($socket);
         if ($s == "")
            echo "Expected ff ff ff ff 66 0a (hex) but got nothing.\n";
         else
            echo "Expected ff ff ff ff 66 0a (hex) but got $s.\n";
         return True;
      }
   }
   return $info['timed_out'];
}

// Connect to master server, return timeout info.
// The socket is passed as reference and thus returned as well.

function master_server_timeout(&$socket, $ip)
{
   $port = MIN_PORT;
   do {
      echo "Connecting to master server \"$ip:$port\".\n";
      $socket = fsockopen("udp://$ip", $port, $errno, $errstr, TIMEOUT);
      if (!$socket) exit("Error $errno : $errstr \n");
      $timeout = query_timeout($socket, "0.0.0.0:0");
      $port = $port + 1;
   } while ($timeout && ($port <= MAX_PORT));
   return $timeout;
}

// Read list with server addresses (IP:port).

function list_not_empty($socket)
    {
    $count = 0;
    $old_a1 = 0; $old_a2 = 0; $old_a3 = 0; $old_a4 = 0; $old_a5 = 0;
    $max_timeouts = 6;
    do
    {
       stream_set_timeout($socket, TIMEOUT);
       $a1 = ord(fread($socket,1));
       $info = stream_get_meta_data($socket);
       if ($info['timed_out'])
       {
          $seed = "$old_a1.$old_a2.$old_a3.$old_a4:$old_a5";
          echo "Seed: $seed\n";
          while (query_timeout($socket, $seed));
          stream_set_timeout($socket, TIMEOUT);
          $a1 = ord(fread($socket,1));
          $info = stream_get_meta_data($socket);
          if ($info['timed_out'])
          {
             echo "Timeout occured.\n";
             break;
          }
          $check_for_duplicate = 1;
       }
       else
          $check_for_duplicate = 0;

       // Let's always read the rest of the address (even if it starts with 0) in
       // order to empty the master server's write buffer. This may avoid subsequent
       // problems, but I'm paranoid here.
       $a2 = ord(fread($socket,1));
       $a3 = ord(fread($socket,1));
       $a4 = ord(fread($socket,1));
       $a5 = ord(fread($socket,1))*256 + ord(fread($socket,1));

       if ($a1 != 0)
       {
          if (($check_for_duplicate==0)||($a1!=$old_a1)||($a2!=$old_a2)||
          ($a3!=$old_a3)||($a4!=$old_a4)||($a5!=$old_a5))
          {
             $count++;
             echo "$count $a1.$a2.$a3.$a4:$a5\n";
          }
          $old_a1 = $a1; $old_a2 = $a2; $old_a3 = $a3; $old_a4 = $a4; $old_a5 = $a5;
       }
    } while ($a1 != 0);
    fclose($socket);

    if ($count != 0) echo "Retrieved $count server addresses.\n";
    return ($count != 0);
}

// Try all master servers until we find one that isn't timing out.

foreach ($master_servers as $ip)
    if ($timeout=master_server_timeout($socket, $ip))
        fclose($socket);
    else
        if (list_not_empty($socket)) break;

?>