File Sharing evolves: DHT, PEX and Magnet explained

For many of us who are reliant of Bit Torrent to access content, significant efforts started by copyright holders have slowly chipped away at the technology and rightfully so as many corporate figures view the technology as a threat to their business model and prefer to follow a raze-and-burn tactic rather than see how to change their business model in light of technological advancements.

But Bit Torrent will be undergoing a dramatic shift soon and here are some new technologies that users may find useful to learn up on.

As it is, Torrents still function by downloading a piece of ‘xxx.torrent’ file from popular file sharing websites such as Pirate Bay, Mininova, Eztv, and so on. With information contained within the files, the torrent client (uTorrent, Azureus, etc) then calculates a ‘torrent hash’ with a fingerprint of the files which is to be downloaded. The large files are often broken down into smaller chunks (a typical 30-minute series can have thousands of fragments), there are thousands of hashes to be calculated. After obtaining the hashes, the client then connects to ‘peers’ to start downloading the file fragments. After downloading, a hash is generated from the fragment and compared to the precomputed one earlier. If they are identical, it means the fragment is downloaded correctly with no errors. Sometimes, due to inefficiencies, the fragment may have an incorrect hash and is rejected. Companies can also poison a torrent swam by injecting false information but this tactic is negated with proper hash checking.

Anyway, it all comes down to this xxx.torrent file, which you have to get from ‘somewhere’ and many authorities have started to crack down on popular sharing sites which host these files. The Pirate Bay is a famous example, having been forced out of Sweden (where their servers are located) due to pressure from copyright holders. With no access to torrent files, Bit Torrent is dead.

Thankfully, three new technologies have surfaced to aid and increase Bit Torrent and they are DHT, PEX and Magnet links. A fourth, so far only present in uTorrent, has also provides a new method to reduce traffic congestion caused by Bit Torrent activities.

Distributed Hash Table

DHT, also know as Distributed Hash Table, is simply another way to foster communication between peers and to discover new peers as they enter a swarm. When activated, your client will connect to a ‘bootstrap’ address such as and from there receive a list of peers also with DHT enabled. From there, your client builds up a list of peers and uses them to exchange information related to peers and to receive addresses of new peers when they join the DHT swarm. It is very similar to technologies used in Limewire and WinMX (old file sharing programs) that have a central node, except with DHT, there is no central node, just a swarm of interconnected peers.

Peer Exchange

PEX, or Peer Exchange, is another method of peer discovery whereby when you manage to connect to a peer, you can get a list of peers that person is connected to and repeat the process. It needs to kick start but once it gets going, it is very efficient at getting you new peers to connect to.


Magnet is a new way of handling torrent files, also known as torrentless trackers. Instead of downloading a file and computing the hash, the website owner precomputes the hash for you and makes the information available in the Magnet link, which you click. When a torrent client detects the Magnet link, it will automatically launch and connect to peers immediately to download the first torrent file. It is worthy to note that torrent files are still important and hold a lot of necessary information needed to start the process of downloading. Therefore it is so far impossible to eliminate torrent files, but Magnet makes the process a lot more automated and is necessary as anti-P2P laws are moving towards the direction of banning torrent files from being hosted all together.


Fourth and last, uTorrent have built into their clients an automatic decongestion mechanism. When it senses that a network is becoming saturated with too much file sharing activity, it will scale back and allow more important duties such as website and video streaming to take precedence. This will be important as P2P activity start to saturate the connections of Internet service providers which use this as excuse to cut off connections of heavy users or invoke fair-use clauses. It will also improve your home network Internet surfing quality, especially when many people are doing P2P activities on the same network.

No doubt, the Bit Torrent community continue to evolve their methods to fight back against copyright holders. It is also important to note that with modern clients such as uTorrent, PEX and DHT comes automatically activated and you don’t need to do anything to enjoy its benefits. Magnet will be come more common and replace torrent files as time goes on, so no action is necessary on your part as well.