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Erlang Bittorrent Client
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ETORRENT is a bittorrent client written in Erlang. The focus is on robustness and scalability in number of torrents rather than in pure speed. ETORRENT is mostly meant for unattended operation, where one just specifies what files to download and gets a notification when they are.

ETORRENT was mostly conceived as an experiment in how easy it would be to write a bittorrent client in Erlang. The hypothesis is that the code will be cleaner and smaller than comparative bittorrent clients.

Note that the code is not yet battle scarred. It has not stood up to the testing of time and as such, it will fail - sometimes in nasty ways and maybe as a bad p2p citizen. Hence, you should put restraint in using it unless you are able to fix eventual problems. If you've noticed any bad behavior it is definitely a bug and should be reported as soon as possible so we can get it away.

Currently supported BEPs:

  • BEP 03 - The BitTorrent Protocol Specification.
  • BEP 04 - Known Number Allocations.
  • BEP 12 - Multitracker Metadata Extension.
  • BEP 23 - Tracker Returns Compact Peer Lists.

Required software:

  • rebar - you need a working rebar installation to build etorrent.
  • Erlang/OTP R13B04 or R14 - the etorrent system is written in Erlang and thus requires a working Erlang distribution to work. It may work with older versions, but has mostly been tested with newer versions.
  • A proper operating system (e.g., some UNIX-derivative). Windows support has never been tested (If you want to port, I'll be happy to help).


  1. make compile - this compiles the source code
  2. make rel - this creates an embedded release in rel/etorrent which can subsequently be moved to a location at your leisure.
  3. edit ${EDITOR} rel/etorrent/etc/app.config - there are a number of directories which must be set in order to make the system work.
  4. check rel/etorrent/etc/vm.args - Erlang args to supply
  5. If you enabled the webui, check rel/etorrent/etc/webui.config
  6. run rel/etorrent/bin/etorrent console
  7. drop a .torrent file in the watched dir and see what happens.
  8. call etorrent:help(). from the Erlang CLI to get a list of available commands.
  9. If you enabled the webui, you can try browsing to its location. By default the location is 'http://localhost:8080'.

Setting up a development environment

When developing for etorrent, you might end up generating a new environment quite often. So ease the configuration, the build infrastructure support this.

  • Create a file rel/vars/etorrent-dev_vars.config based upon the file rel/vars.config.
  • run make compile etorrent-dev
  • run make console

Notice that we -pa add ../../apps/etorrent/ebin so you can l(Mod) files from the shell directly into the running system after having recompiled them.


Either mail them to (We are currently lacking a mailing list) or use the issue tracker:

Reading material for hacking Etorrent:

  • Protocol specification - BEP0003: This is the original protocol specification, tracked into the BEP process. It is worth reading because it explains the general overview and the precision with which the original protocol was written down.

  • Bittorrent Enhancement Process - BEP0000 The BEP process is an official process for adding extensions on top of the BitTorrent protocol. It allows implementors to mix and match the extensions making sense for their client and it allows people to discuss extensions publicly in a forum. It also provisions for the deprecation of certain features in the long run as they prove to be of less value.

  • An alternative description of the protocol. This description is in general much more detailed than the BEP structure. It is worth a read because it acts somewhat as a historic remark and a side channel. Note that there are some commentary on these pages which can be disputed quite a lot.

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