BitTorrent: Download not starting

Question

I am trying to implement a bittorrent tracker in Laravel. However, I am stuck at the moment as the download won't start. There is one peer which it appears to be seeding and I am 100% sure that it is connectable. But, when I run a second client on a different machine, the download won't start. It is stuck at "Connecting to peers" (uTorrent).

From the tracker I am sending the following response when the client makes an announce:

d8:intervali1000e12:min intervali300e5:peers18:�ؤ�i�ؑ�XÚJU�6e

In the downloading client I have the following data:

Here's my announce code:

<?php

namespace App\Http\Controllers\Announce;

use App\Helpers\BencodeHelper;
use App\Models\Peer;
use App\Models\PeerTorrent;
use App\Models\Torrent;
use App\Models\User;
use Illuminate\Http\Request;
use Illuminate\Http\Response;
use Illuminate\Routing\Controller;
use Illuminate\Support\Facades\Input;
use Illuminate\Support\Facades\Log;

class AnnounceController extends Controller
{
    const __INTERVAL = 1000;
    const __TIMEOUT = 120;
    const __INTERVAL_MIN = 60;
    const __MAX_PPR = 20;

    public function announce(Request $request)
    {
        Log::info($request->fullUrl());
        $status = 200;
        $content = "";
        $passkey = Input::get('passkey');
        $peer_id = Input::get('peer_id');
        $port = Input::get('port');
        $info_hash = Input::get('info_hash');
        $downloaded = Input::get('uploaded') ? intval(Input::get('uploaded')) : 0;
        $uploaded = Input::get('uploaded') ? intval(Input::get('uploaded')) : 0;
        $left = Input::get('left') ? intval(Input::get('left')) : 0;
        $compact = Input::get('compact') ? intval(Input::get('compact')) : 0;
        $no_peer_id = Input::get('no_peer_id') ? intval(Input::get('no_peer_id')) : 0;

        $ipAddress = '';
        // Check for X-Forwarded-For headers and use those if found
        if (isset($_SERVER['HTTP_X_FORWARDED_FOR']) && ('' !== trim($_SERVER['HTTP_X_FORWARDED_FOR']))) {
            $ipAddress = (trim($_SERVER['HTTP_X_FORWARDED_FOR']));
        } else {
            if (isset($_SERVER['REMOTE_ADDR']) && ('' !== trim($_SERVER['REMOTE_ADDR']))) {
                $ipAddress = (trim($_SERVER['REMOTE_ADDR']));
            }
        }

        $port = $_SERVER['REMOTE_PORT'];
        /*if(!$port || !ctype_digit($port) || intval($port) < 1 || intval($port) > 65535)
        {
            $content = BencodeHelper::track("Invalid client port.");
            $status = 401;
            return (new Response(AnnounceController::track($content), $status))
                ->header('Content-Type', $value);
        }

        if ($port == 999 && substr($peer_id, 0, 10) == '-TO0001-XX') {
            die("d8:completei0e10:incompletei0e8:intervali600e12:min intervali60e5:peersld2:ip12:72.14.194.184:port3:999ed2:ip11:72.14.194.14:port3:999ed2:ip12:72.14.194.654:port3:999eee");
        }*/


        if (!$passkey) {
            $content = BencodeHelper::track("Missing passkey.");
            $status = 401;
            return (new Response(AnnounceController::track($content), $status))
                ->header('Content-Type', $value);
        }


        $torrent = Torrent::getByInfoHash(sha1($info_hash));
        if (!$torrent || $torrent == null) {
            $content = "Torrent not registered with this tracker.";
            $status = 404;
            return (new Response(AnnounceController::track($content), $status))
                ->header('Content-Type', $value);
        }

        $user = User::has('passkeys', '=', $passkey)->get();

        if ($user == null) {
            $content = BencodeHelper::track("Invalid passkey.");
            $status = 401;
            return (new Response(AnnounceController::track($content), $status))
                ->header('Content-Type', $value);
        }

        $peer = Peer::getByHashAndPasskey(bin2hex($peer_id), $passkey);

        if ($peer == null) {
            $peer = Peer::create([
                'hash' => bin2hex($peer_id),
                'user_agent' => $_SERVER['HTTP_USER_AGENT'],
                'ip_address' => $ipAddress,
                'passkey' => $passkey,
                'port' => $port
            ]);
        }

        if (!$info_hash || strlen($info_hash) != 20) {
            $content = BencodeHelper::track("Invalid info_hash.");
            $status = 401;
            return (new Response(AnnounceController::track($content), $status))
                ->header('Content-Type', $value);
        }


        $peer_torrent = PeerTorrent::getByPeerAndTorrent($peer, $torrent);

        if ($peer_torrent == null) {
            $peer_torrent = PeerTorrent::create([
                'peer_id' => $peer->id,
                'torrent_id' => $torrent->id,
                'uploaded' => $uploaded,
                'downloaded' => $downloaded,
                'left' => $left,
                'stopped' => false
            ]);

        } else {
            $peer_torrent->uploaded = $uploaded;
            $peer_torrent->downloaded = $downloaded;
            $peer_torrent->left = $left;
            $peer_torrent->save();
        }

        $seeders = $torrent->getSeedersCount();
        $leechers = $torrent->getLeechersCount();
        $resp = "";
        if ($compact != 1) {
            $resp = "d" . $this->benc_str("interval") . "i" . AnnounceController::__INTERVAL . "e" . $this->benc_str("peers") . "l";
        } else {
            $resp = "d" . $this->benc_str("interval") . "i" . AnnounceController::__INTERVAL . "e" . $this->benc_str("min interval") . "i" . 300 . "e5:" . "peers";
        }

        $peer = array();

        $peer_num = 0;
        foreach ($torrent->getPeersArray() as $row) {
            if ($compact != 1) {
                if ($row["peer_id"] === $peer->hash) {
                    continue;
                }

                $resp .= "d" . $this->benc_str("ip") . $this->benc_str($row['ip']);

                if ($no_peer_id == 0) {
                    $resp .= $this->benc_str("peer id") . $this->benc_str($row["peer_id"]);
                }

                $resp .= $this->benc_str("port") . "i" . $row["port"] . "e" . "e";

            } else {
                $peer_ip = explode('.', $row["ip"]);
                $peer_ip = pack("C*", $peer_ip[0], $peer_ip[1], $peer_ip[2], $peer_ip[3]);
                $peer_port = pack("n*", (int)$row["port"]);
                $time = intval((time() % 7680) / 60);

                if ($left == 0) {
                    $time += 128;
                }

                $time = pack("C", $time);
                $peer[] = $time . $peer_ip . $peer_port;
                $peer_num++;
            }
        }

        if ($compact != 1) {
            $resp .= "ee";
        } else {
            $o = "";
            for ($i = 0; $i < $peer_num; $i++) {
                $o .= substr($peer[$i], 1, 6);
            }
            $resp .= strlen($o) . ':' . $o . 'e';
        }

        $this->benc_resp_raw($resp);
    }

    public function benc_resp($d)
    {
        return $this->benc_resp_raw($this->benc(array('type' => 'dictionary', 'value' => $d)));
    }

    public function benc_resp_raw($x)
    {
        header("Content-Type: text/plain");
        header("Pragma: no-cache");

        if ($_SERVER['HTTP_ACCEPT_ENCODING'] == 'gzip') {
            header("Content-Encoding: gzip");
            echo gzencode($x, 9, FORCE_GZIP);
        } else {
            echo $x;
        }
    }

    function benc($obj)
    {
        if (!is_array($obj) || !isset($obj["type"]) || !isset($obj["value"]))
            return;
        $c = $obj["value"];
        switch ($obj["type"]) {
            case "string":
                return $this->benc_str($c);
            case "integer":
                return $this->benc_int($c);
            case "list":
                return $this->benc_list($c);
            case "dictionary":
                return $this->benc_dict($c);
            default:
                return;
        }
    }

    public function benc_str($s)
    {
        return strlen($s) . ":$s";
    }

    public function benc_int($i)
    {
        return "i" . $i . "e";
    }

    public function benc_list($a)
    {
        $s = "l";
        foreach ($a as $e) {
            $s .= $this->benc($e);
        }
        $s .= "e";
        return $s;
    }

    public function benc_dict($d)
    {
        $s = "d";
        $keys = array_keys($d);
        sort($keys);
        foreach ($keys as $k) {
            $v = $d[$k];
            $s .= $this->benc_str($k);
            $s .= $this->benc($v);
        }
        $s .= "e";
        return $s;
    }


    public function hex2bin($hex)
    {
        $r = '';
        for ($i = 0; $i < strlen($hex); $i += 2) {
            $r .= chr(hexdec($hex{$i} . $hex{($i + 1)}));
        }
        return $r;
    }
}

I am not quite sure what am I missing here.

Answer 1

   $port = $_SERVER['REMOTE_PORT'];

I think the problem is that the tracker instead of register the port that the connecting peer sends in the announce string, the tracker register the remote port that the peer is connecting from.
That is almost certainly the wrong port to use.

Answer 2

Maybe it's because you constantly set

->header('Content-Type', $value);

without ever setting $value? So the "Announce-Response" is malformed?