CODEWITHSUNDEEP
rubyp2pbittorrentdht
tekknolagi
tekknolagi

Reputation: 11012

Connect to torrent "swarm" or DHT with ruby

I'm probably lacking in some fundamental understanding of how BitTorrent, DHT, and the "swarm" work, as I'm not even sure if DHT and the "swarm" are one and the same.

However, I'm trying to find peers, the number of peers, and some statistics about a torrent from its magnet link (and hash).

I've looked for some libraries to accomplish this, but they seem either outdated or unrelated, or just bencode things.

How do I go about connecting and requesting information? A brief explanation would be delightful.

Upvotes: 2

Views: 1442

Answers (1)

the8472
the8472

Reputation: 43052

official specs: http://www.bittorrent.org/beps/bep_0000.html
non-official spec: http://wiki.theory.org/BitTorrentSpecification

BEncoding is a data serialization format used in bittorrent for several purposes

The DHT is a global, decentralized, iterative, UDP-based lookup system which can be used to locate clients participating in a particular swarm based on an infohash, which can be either obtained directly from a magnet link or calculated from a .torrent metadata file.

If you have the announce URL for a tracker (an optional part of the torrent file or the magnet link) you can obtain client addresses directly from a tracker.

Once you have obtained client addresses for a particular swarm you can connect to them - or they will connect to you if you have announced yourself to the DHT/a responsible tracker - using the bittorrent wire protocol, which is basically an asynchronous, binary messaging protocol.

To get a fully-functioning, state-of-the-art bittorrent client you have to implement the following:

  • a DHT node (bencoding over UDP)
  • tracker announce and scrape protocol (uses bencoding over HTTP and a custom binary prtocol over UDP)
  • the bittorrent wire protocol (custom binary protocol over TCP with an optional extension layer. some of the messages are bencoded. A congestion-avoiding UDP-based transport protocol called µTP also exists as alternative to TCP)
  • a torrent file parser (bencoding, obviously)
  • general stuff like queueing active torrents, file management, highly concurrent network IO

This is a lot of work which to my knowledge has not been done in ruby. So either you have a lot ahead of yourself or you might want to use a bittorrent library written in a different language (e.g. libtorrent) or interface with a client providing a web service (e.g. transmission).

Upvotes: 5

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