CODEWITHSUNDEEP
node.jsmongodbtorrent
Bubun
Bubun

Reputation: 456

How to create torrent files from magnet link or infohash

I am trying to create a torrent search engine. yet I found a way to collect torrent infohashes from DHT network. My question is how can I extract .torrent files from them? I have a MongoDB collection contains 1M-1.5M(Growing Very Quickly) torrent info hash.

Upvotes: 3

Views: 4114

Answers (2)

Ian Boyd
Ian Boyd

Reputation: 256591

Given just an infohash, e.g.:

  • 463e408429535139a0bbb5dd676db10d5963bf05

you can use:

BEP: 9 - Extension for Peers to Send Metadata Files

The purpose of this extension is to allow clients to join a swarm and complete a download without the need of downloading a .torrent file first. This extension instead allows clients to download the metadata from peers. It makes it possible to support magnet links, a link on a web page only containing enough information to join the swarm (the info hash).

You use DHT to find the distributed trackers.
Then you use the distributed trackers to find the peers who have the torrent.
Then you can download the torrent metadata from a peer.

You send the bencoded metadata request to the peer:

{ 
   "msg_type": 0,      ; 0==>request
   "piece": 0
}

Upvotes: 2

Bubun
Bubun

Reputation: 456

I solved the problem myself. I used webtorrent npm package and also created an algorithm to loop through the whole database and added the magnet link in the download task. once the client gets metadata, I just saved it to the torrent file and canceled the download.

Well, The code is not yet fully production ready. I'll Post The Code Snippet here afterward. Thank You!

UPDATE: I am using this class to download Torrent file from magnet

const Discovery = require('torrent-discovery');
const Protocol = require('bittorrent-protocol');
const ut_metadata = require('ut_metadata');
const addrToIPPort = require('addr-to-ip-port');
const net = require('net');

class TorrentDownloader {
  constructor(port, trackers, timeout) {
    this.SELF_HASH = '4290a5ff50130a90f1de64b1d9cc7822799affd5';
    this.port = port | 6881;
    this.trackers = trackers;
    this.timeout = timeout | 80000;
  }

  downloadTorrent(infoHash) {
    let self = this;
    return new Promise((resolve, reject) => {
      let dis = new Discovery({infoHash: infoHash, peerId: this.SELF_HASH, port: this.port, dht: true, announce: this.trackers})
          .on('peer', function (peer) {
            const peerAddress = {address: addrToIPPort(peer)[0], port: addrToIPPort(peer)[1]};
            // console.log(`download metadata from peer ${peerAddress.address}:${peerAddress.port}`);
            self.getMetadata(peerAddress, infoHash, resolve);
          });
      setTimeout(() => {
        dis.destroy();
        reject(new Error("Torrent Timeout"))
      }, this.timeout)
    })
  }

  getMetadata(peerAddress, infoHash, resolve) {
    const socket = new net.Socket();
    socket.setTimeout(this.timeout);
    socket.connect(peerAddress.port, peerAddress.address, () => {
      const wire = new Protocol();

      socket.pipe(wire).pipe(socket);
      wire.use(ut_metadata());
      wire.handshake(infoHash, this.SELF_HASH, {dht: true});
      wire.on('handshake', function (infoHash, peerId) {
        wire.ut_metadata.fetch();
      });
      wire.ut_metadata.on('metadata', function (rawMetadata) {
        resolve(rawMetadata);
        wire.destroy();
        socket.destroy()
      })
    });
    socket.on('error', err => {
      socket.destroy();
    });
  }
}

module.exports = TorrentDownloader;

Upvotes: 1

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