One File Tracker

<?php
/* One-file(+MySQL) BitTorrent Tracker
 * Written by kenkeiras
 *
 * This program is free software. It comes without any warranty, to
 * the extent permitted by applicable law. You can redistribute it
 * and/or modify it under the terms of the Do What The Fuck You Want
 * To Public License, Version 2, as published by Sam Hocevar. See
 * http://sam.zoy.org/wtfpl/COPYING for more details. */

/* MySQL database configuration */
/* Database host */
$dbhost = 'localhost';

/* Database user */
$dbuser = "one_file_tracker";

/* Database password */
$dbpass = "one_file_tracker";

/* Database name */
$dbname = "one_file_tracker";

/* Entry timeout (in seconds)
 * after this time, peer data will be no longer sended
 */
$timeout = 3600;

/* Peer table name
 * Columns:
 *  Peer_id: char(28)
 *  info_hash: char(28)
 *  port: smallint unsigned
 *  uploaded: int(1)
 *  downloaded: int(1)
 *  to_go: int(1)
 *  ip: varchar(15)
 *  peer_key: varchar(255)
 *  completed: boolean
 *  last_update: int(1)
 *
 * Keys:
 *  Peer_id
 *  info_hash
 *
 * create table peers( peer_id char(28), info_hash char(28), port smallint
 *             unsigned, uploaded int(1), downloaded int(1), to_go int(1),
 *               ip varchar(15), peer_key varchar(255), completed boolean,
 *                     last_update int(1),KEY (peer_id), KEY (info_hash));
 */
$dbtable = "peers";

/* Default number of peers returned
 *  protocol's default is 50
 */
$default_peer_num = 50;

/* Interval in seconds that the client should wait between
 * sending regular requests to the tracker
 */
$interval = 300;

/* Max peer returned */
$max_peer_num = 100;

/* Prints a number in network order */
function hton_spwn($n, $c){
    for($i=$c-1;$i>=0;$i--){
        echo chr($n>>($i*8));
        $n = $n % (1<<($i*8));
    }
}

/* Sends an error in the BitTorrent'ish way */
function bt_die($s){
    $fail="failure reason";
    die( "d".strlen($fail).":".$fail.strlen($s).$s."e" );
}

/* Sends the peer list */
function send_bencoded_peers($d){
    print "d";
    $int = "interval"; // Connection interval
    echo strlen($int).":".$int."i".$d['interval']."e";

    if (!$d['stop']){
        $comp = "complete"; // Seeds
        echo strlen($comp).":".$comp."i".$d['complete']."e";

        $incomp = "incomplete"; // Leechers
        echo strlen($incomp).":".$incomp."i".$d['incomplete']."e";
    }

    $peers = "peers";
    echo strlen($peers).":$peers"; // Peer list
    $has_peers = FALSE;
    if ($d['compact']){
        echo (6 * mysql_num_rows($d['peers']) ).":";
    }
    else{
        echo "l";
    }
    while ( ($n = mysql_fetch_array($d['peers'])) !== FALSE ){
        $has_peers = TRUE;
        if ($d['compact']){ // Compact format
            echo hton_spwn(ip2long($n['ip']),4);
            echo hton_spwn($n['port'],2);
        }
        else{ // Normal format
            $url_peer = urlencode($n['peer_id']);
            echo "d";
            if (strlen($url_peer) > 0){
                echo "2:id".strlen($url_peer).":".$url_peer;
            }
            echo "2:ip".strlen($n['ip']).":".$n['ip'];
            echo "4:port".strlen($n['port']).":".$n['port']."e";
        }
    }
    if (!$d['compact']){
        echo "e";
    }
    echo "e";
}

/* The true tracker function */
function tracker($dbhost, $dbuser,$dbpass,$dbname,$dbtable){

    header('Content-type: text/plain');

    $db = mysql_connect( $dbhost, $dbuser, $dbpass ) or
                              bt_die("Error connecting to database");

    mysql_select_db( "$dbname", $db ) or
                                bt_die("Error selecting a database");

    /* Delete timeouted peers */
    mysql_query( "delete from $dbtable where ".
                "last_update<".(time()-$GLOBALS['timeout']).";") or
                                    bt_die("Error updating database");

    /* SQL-safe values */
    $peer_id = base64_encode($_GET['peer_id']);
    $info_hash = base64_encode($_GET['info_hash']);
    $port = intval($_GET['port']);
    $uploaded = intval($_GET['uploaded']);
    $downloaded = intval($_GET['downloaded']);
    $to_go = intval($_GET['left']);
    $ip = $_SERVER['REMOTE_ADDR'];
    $peer_key = base64_encode($_GET['key']);
    $stopping = FALSE;

    /* Checks if it needs to add or just update the rows */
    $res = mysql_query( "select count(1) as count from $dbtable where ".
                "peer_id='$peer_id' and info_hash='$info_hash';") or
                                    bt_die("Error reading database");

    $num = mysql_fetch_array($res);
    if ( isset( $_GET['event'])&&($_GET['event']=="stopped")){
        mysql_query("delete from $dbtable ".
                   "where peer_id='$peer_id' and info_hash='$info_hash'".
                   "and peer_key='$peer_key';") or
                     bt_die( "Error deleting you from available peers");
        $stopping = TRUE;
    }
    $state = "";
    if ((isset($_GET['event'])&&($_GET['event']=="completed"))
         or ($to_go < 1)){

        $state = ",completed=true";
    }
    elseif (isset($_GET['event'])&&($_GET['event']=="started")){
        $state = ",completed=false";
    }

    if ( !$stopping ){
        /* Stores the data */
        if ( $num['count'] == 0 ){
            mysql_query( "insert into $dbtable set ".
                    "last_update=".time().",".
                    "peer_id='$peer_id',info_hash='$info_hash',".
                    "uploaded=$uploaded,peer_key='$peer_key',".
                    "downloaded=$downloaded,to_go=$to_go,ip='$ip',".
                    "port=$port $state;") or
                        bt_die( "Error adding you to the peer database");
        }
        else{
            mysql_query( "update $dbtable set uploaded=$uploaded,".
                    "last_update=".time().",".
                    " downloaded=$downloaded,to_go=$to_go,ip='$ip', ".
                    "port=$port $state ".
                    "where peer_id='$peer_id' and info_hash='$info_hash' ".
                    "and peer_key='$peer_key';") or
                                       bt_die("Error updating database");
        }
    }
    /* Reads the total number of peers */
    $res = mysql_fetch_array(mysql_query("select count(1) as count ".
                                     " from $dbtable ".
                                     " where info_hash='$info_hash';"));

    $total_peers = $res['count'];
    $peerNum = $GLOBALS["default_peer_num"];
    if ( isset( $_GET['numwant'] ) &&
                        $_GET['numwant'] <= $GLOBALS['max_peer_num']){

        $peerNum = $_GET['numwant'];
    }
    $top = $total_peers > $peerNum?$total_peers - $peerNum:0;
    $off = rand(0, $top);

    /* Takes some random peers */
    $peers = mysql_query("select peer_id,ip,port".
                         " from $dbtable ".
                         " where peer_id!='$peer_id'".
                         " and info_hash='$info_hash' ".
                         " limit $off,$peerNum;");

    /* Reads how many of the hava completed the download */
    $comp = mysql_fetch_array(mysql_query("select count(1) as count ".
                                        " from $dbtable ".
                                        " where info_hash='$info_hash' and".
                                        " peer_id!='$peer_id' and ".
                                        " completed=True ;"));
    /* Stores all in a dictionary */
    $dict = array( 'interval'=> $GLOBALS['interval']."",
                   'complete'=> $comp['count'],
                   'incomplete'=> $total_peers - $comp['count'],
                   'peers' => $peers,
                   'compact' => isset($_GET['compact']) &&
                                    ($_GET['compact'] == "1")?TRUE:FALSE,
                   'stop' => $stopping);

    /* And sends it */
    send_bencoded_peers($dict);

    mysql_close();
}

if (isset($_GET) && isset($_GET['peer_id']) && isset($_GET['peer_id'])){
    tracker($dbhost, $dbuser,$dbpass,$dbname,$dbtable);
}
else{
    echo  <<< __EOF__
<html><head><title>One File Tracker</title></head>
<body>Are you a BitTorrent client? &not;&not;</body></html>
__EOF__;

}
?>