Sending scrape request for getting torrent's seeds and peers

Question

I have been trying to create a torrent site but I'm stuck with the following. How to send torrent scrape request to get its seeder and leechers?

I have a PHP class function that provides me announce list.

public function getTrackers() {
    // Load tracker list
    $trackerlist = array();

    if ( $this->torrent->get_value('announce-list') )
    {
        $trackers = $this->torrent->get_value('announce-list')->get_plain();
        while ( list( $key, $value ) = each( $trackers ) )
        {
            if ( is_array( $value->get_plain() ) ) {
                while ( list( $key, $value2 ) = each( $value ) )
                {
                    while ( list( $key, $value3 ) = each( $value2 ) )
                    {
                        array_push( $trackerlist, $value3->get_plain() );
                    }
                }
            } else {
                array_push( $trackerlist, $value->get_plain() );
            }
        }
    }
    else if ( $this->torrent->get_value('announce') )
    {
        array_push( $trackerlist, $this->torrent->get_value('announce')->get_plain() );
    }

    return $trackerlist;
}

This code is based on the data encoded by the bencode.php. How to show Seeds and Peers of every consecutive announce url like this?

Annouce Url | Seeds : No. | Peers: No.     
Annouce Url | Seeds : No. | Peers: No.     
Annouce Url | Seeds : No. | Peers: No. 
and so on.....

Answer 1

I can't help you with code, due to my limited experience with PHP, but dealing with HTTP trackers should be fairly easy.

Get the announce URL, search and replace the word "announce" with "scrape" and add ?infohash=<url-encoded-binary-20-byte-long-infohash> as parameter (you may add as many infohash= to your query, divided by ampersand. Make a HTTP call to that resulting URL and read your bencoded answer. It will contain all the requested info-hashes with their respective downloads, seeders ('complete' in tracker's vocabulary) and leechers ('incomplete'). HTTP scrape is very well documented.

Dealing with UDP trackers is somewhat more complicated, because this binary form of communication happens at much lower level. Check the full description of UDP tracker protocol.