External trackers list support, info-dictionary receiving speedup for magnet links by early trackers client init

[arestov]

Now we can use manual trackers list to speedup peers finding. Which accelerates start of downloading and with early trackers client init info-dictionary receiving.

engine('magnet://...', 
    {trackers: [
        'udp://tracker.openbittorrent.com:80',
        'udp://tracker.ccc.de:80',
        'udp://tracker.istole.it:80',
        'udp://tracker.publicbt.com:80'
    ]});

[arestov]

@asapach done

[asapach]

I'd like to preserve existing behavior: if opts.tracker: false, no trackers should be used, regardless of opts.trackers option.

[arestov]

in suggested code we can do

{
  tracker: false,
  trackers: null
}

to disable trackers completely.

And we can

{
  tracker: false,
  trackers: [...]
}

to use own list of trackers instead of list from torrent file.

But if tracker disables trackers how we can use own list of trackers instead of list form torrent file. I thought that this way is more flexible and better for API. What do you think?

[BastienClement]

Seems like a good point for me.

[asapach]

I'm merging this PR into the trackers branch: https://github.com/mafintosh/torrent-stream/tree/trackers I've added a couple of tests and they are failing at the moment.

[asapach]

Ran into an issue with bittorent-tracker: feross/bittorrent-tracker#19, tests still failing.

[arestov]

Now tests pass. And if we call .listen immediately after engine instance has been created we do not recreate tracker. (With process.nextTick help)

[asapach]

@arestov, I'm trying to test this on public trackers (TPB, openbittorent, etc.), but always get connection refused (might be my ISP). Does it work for you?

[arestov]

Following code works for me

var Eng = require('./index');
var eng = Eng('magnet:?xt=urn:btih:2e0ba00b6ae7d68d03a61e682fe85e6964796b27&dn=Duck%20Sauce%20%E2%80%93%20NRG', {
    dht: false,
    trackers: [
        'udp://tracker.openbittorrent.com:80',
        'udp://tracker.ccc.de:80',
        'udp://tracker.istole.it:80',
        'udp://tracker.publicbt.com:80'
    ]
});
eng.on('ready', function() {
    console.log('done')
});

[asapach]

This PR has been merged into #50. Let's continue discussion there.