Connecting to torrent trackers / peers

I'm currently trying to implement a minimal torrent client, in nodeJS.

I'm reading through this specification: https://wiki.theory.org/index.php/BitTorrentSpecification

I've got 2 magnet URIs:

magnet:?xt=urn:btih:633ab5b0cc27218bca2f9fec9b68ae4f7cbf0c5f&dn=dmb2017-05-31.dpa4021.flac16


xt=urn:btih:633ab5b0cc27218bca2f9fec9b68ae4f7cbf0c5f
dn=dmb2017-05-31.dpa4021.flac16

---

magnet:?xt=urn:btih:9f9165d9a281a9b8e782cd5176bbcc8256fd1871&dn=Ubuntu+16.04.1+LTS+Desktop+64-bit&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Fzer0day.ch%3A1337&tr=udp%3A%2F%2Fopen.demonii.com%3A1337&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Fexodus.desync.com%3A6969

xt=urn:btih:9f9165d9a281a9b8e782cd5176bbcc8256fd1871
dn=Ubuntu+16.04.1+LTS+Desktop+64-bit
tr=udp://tracker.leechers-paradise.org:6969
tr=udp://zer0day.ch:1337
tr=udp://open.demonii.com:1337
tr=udp://tracker.coppersurfer.tk:6969
tr=udp://exodus.desync.com:6969

From what I've read, the tracker is used to find peers, from which data is downloaded. How would one download the first torrent then? It has no tracker.

How do I actually do conduct this connection?

The specification has nothing on magnet links, and states that trackers can be used via the HTTP(S) protocols, but these are clearly UDP.

I gave a stab at this:

var PORT = 6969 ;
var HOST = 'tracker.leechers-paradise.org';

var dgram = require('dgram');
var message = new Buffer("xt=urn:btih:9f9165d9a281a9b8e782cd5176bbcc8256fd1871");

var client = dgram.createSocket('udp4');

client.on('listening', function () {
    var address = client.address();
    console.log('UDP Server listening on ' + address.address + ":" + address.port);
});

client.on('message', function (message, remote) {

    console.log(remote.address + ':' + remote.port +' - ' + message);

});

client.send(message, 0, message.length, PORT, HOST, function(err, bytes) {

    if (err) throw err;
    console.log('UDP message sent to ' + HOST +':'+ PORT);
    console.log(bytes);

});

Obviously, this doesn't work, but I can't find any documentation to help.

via Tobiq