torrent explained

C

Costas

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A torrent tracker is a server that helps facilitate the communication between peers in a BitTorrent network. The primary role of a tracker is to keep track of which peers (users) are sharing a specific torrent file. It maintains a list of active peers and their IP addresses. They are a single point of control. If the tracker goes down, users may have difficulty finding peers. This limitation led to the development of decentralized methods like DHT and PEX.


Peer Exchange (PEX) established 2000
Is not fully decentralized like DHT. It relies on existing connections between peers to share information about other peers. When a peer connects to another peer, it can exchange lists of peers it knows about.

Distributed Hash Tables (DHTs) established 2005
Is a fully decentralized system. It allows peers to find each other without relying on a central tracker. Each peer in the network can act as both a client and a server, storing and retrieving information about other peers. The DHT allows peers to discover each other and share information about the files they have, but it does not store the actual content or maintain a central list of peers. Instead, it facilitates the process of finding peers who have the desired content. Once a peer is connected to the network, it can query other peers and participate in the DHT without needing to rely on any central authority or server.


The conventional approach to discovering peers in a torrent consists of requesting the list of peers in the torrent from a centralized entity known as the tracker. This centralized approach to peer discovery is not scalable, especially for trackers that keep track of millions of peers for thousands of files.

Modern BitTorrent clients (e.g., uTorrent, Azureus, BitComet) additionally provide decentralized peer discovery using Distributed Hash Tables (DHTs) and Peer Exchange (PEX). A DHT provides the same tracking service as that of the central tracker in a distributed manner. Peers can query the DHT interface to obtain peer lists. Different from DHT, PEX allows peers in a torrent to exchange lists of active peers directly with each other. PEX has been first implemented in Azureus to reduce the load on trackers and later also adopted by other popular clients (uTorrent etc).

In order to alleviate the load on trackers, two decentralized approaches to peer-discovery are being used by a number of clients: Distributed Hash Tables (DHTs) and Peer Exchange (PEX). A DHT is a database distributed over a network of computers, referred to as nodes. Note that, in order to join a DHT, a peer should first know a bootstrapping node in that DHT. Currently, the BitTorrent ecosystem consists of two major DHTs: the Azureus DHT and the Mainline DHT. The Azureus DHT is used only by Azureus clients (now Vuze) and the Mainline DHT is used by all the other clients that support the DHT feature, including uTorrent, BitComet.

Magnet Links can utilize both DHT and trackers for peer discovery, which can enhance their resilience to tracker failures. In nutshell is :
magnet:?xt=urn:btih:<info_hash>&dn=<name>&tr=<tracker_url>

info_hash is the sha1 of the torrent file.
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open trackers
https://www.demonii.com/
http://opentrackr.org/
http://www.cyberia.is/tracker.html

torrent creators
https://kimbatt.github.io/torrent-creator/
https://github.com/kz26/dottorrent-gui
https://sourceforge.net/projects/hcreatetorrent/
https://github.com/adriengibrat/torrent-rw (used by yts)
https://github.com/arokettu/torrent-file
nowdays all torrent applications support it.

torrent editors
http://torrenteditor.com/
https://sourceforge.net/projects/torrent-file-editor/
https://sites.google.com/site/ultimasites/bencode-editor

magnetlink generators
https://nutbread.github.io/t2m/
https://madeby.lynx.pink/magnets/
https://www.hashtomagnet.com/
https://hardrisk.github.io/magnet/
https://magnetlinkgenerator.com/

howto
video - shows also how to be a tracker with qBittorrent
https://www.wikihow.com/Create-a-Torrent

conclusion :
you can create a torrent without trackers and then generate a magnet link.
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Local Peer Discovery (LPD) - is a feature used in BitTorrent protocols that allows peers on the same local network (LAN)
uTP - is used to allow other programs on your computer to use bandwidth equally.


- After reading it I wonder why do I need trackers at all if I have DHT with PEX enabled by default?
- You don't need trackers for public torrents. Like you said, DHT/PEX already handles this. That said trackers can be useful to start a torrent faster but ultimately you'll find the same seeds with DHT/PEX. Just make sure your torrent client is connectable (port forwarded) to maximize your ability to connect to different peers.
- Do you add any trackers to your torrents?
- Nope. source
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The easiest way to think about DHT is to imagine it as a form of ‘super tracker’, in some ways a lot like WinMX and Kazaa of old. A large ad-hoc network of peers pass on information requests about torrents without a central server, meaning no control or single point of failure. No information about the contents or even the names of torrents are passed around, making this legal and hard to shut down. When DHT is enabled (certainly in uTorrent) it connects to a bootstrap node (such as router.utorrent.com or router.bittorrent.com for mainline, or dht.aelitis.com for Vuze) and uses that to enter the DHT ‘swarm’. It’s handed a set of DHT nodes and uses that to build up a small group of connected nodes. Those nodes are then used to get peers. No tracker is required at any time. source
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(2006) Torrentfreak - BitTorrent acronyms
(2009) Torrentfreak - Busting Common Trackerless Torrent Myths
(2005-2016) all about torrent, webarchive collection - pdf


links :
 
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