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Revision 17 as of 2007-04-11 17:12:15
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Editor: h10n6c1o1052
Comment: Capture file of two torrent clients communicationg without DHT or peer exch.
Revision 18 as of 2007-04-11 18:31:02
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Editor: GuyHarris
Comment: Point to the sample captures on the SampleCaptures page.
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== Example capture file == == Example capture files ==
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attachment:BITTORRENT.pcap attachment:SampleCaptures/BitTorrent.Transfer1.cap (Microsoft Network Monitor) Here's a capture with a few BitTorrent packets; it contains some small packets I got whilst downloading something on BitTorrent.

attachment:SampleCaptures/BITTORRENT.pcap (libpcap) Capture file of two torrent clients communicationg without DHT or peer exch.

BitTorrent

BitTorrent is a protocol designed for transferring files. It is peer-to-peer in nature, as users connect to each other directly to send and receive portions of the file. However, there is a central server (called a tracker) which coordinates the action of all such peers. The tracker only manages connections, it does not have any knowledge of the contents of the files being distributed, and therefore a large number of users can be supported with relatively limited tracker bandwidth.

A recent extension to BitTorrent is the DHT ("distributed sloppy hash table" or simply called UDP tracker) protocol. A UDP based peer to peer tracker protocol.

History

In April 2001 Bram Cohen designed the BitTorrent protocol, which he implemented summer 2002. The first program to use the protocol was the original [http://www.bittorrent.com/download BitTorrent client]. Today many applications are availiable, and the protocol is widely used.

Protocol dependencies

  • ["TCP"]: Typically, BitTorrent uses ["TCP"] as its transport protocol. The well known TCP port for BitTorrent traffic is 6881-6889 (and 6969 for the tracker port). The DHT extension (peer2peer tracker) uses various UDP ports negotiated by the peers.

Example traffic

XXX - Add example traffic here (as plain text or Wireshark screenshot).

Wireshark

The BitTorrent dissector is (fully functional, partially functional, not existing, ... whatever the current state is). The DHT extension is currently not decoded.

Preference Settings

*["Reassemble BitTorrent messages spanning multiple TCP segments"] *["Decode the peer_id of the handshake messages"]

Example capture files

attachment:SampleCaptures/BitTorrent.Transfer1.cap (Microsoft Network Monitor) Here's a capture with a few BitTorrent packets; it contains some small packets I got whilst downloading something on BitTorrent.

attachment:SampleCaptures/BITTORRENT.pcap (libpcap) Capture file of two torrent clients communicationg without DHT or peer exch.

Display Filter

A complete list of BitTorrent display filter fields can be found in the [http://www.wireshark.org/docs/dfref/b/bittorrent.html display filter reference]

  • Show only the BitTorrent based traffic:

     bittorrent 

Note: implemented in Wireshark post 0.10.12!

Capture Filter

You cannot directly filter BitTorrent protocols while capturing. However, if you know the ["TCP"] port used (see above), you can filter on that one.

  • Capture only the BitTorrent tracker traffic over one of the default ports (e.g. 6881):

     tcp port 6881 

    Capture the BitTorrent tracker traffic over the range of default ports (e.g. 6881-6889):

     tcp portrange 6881-6889 

    when using libpcap 0.9.1 or later or WinPcap 3.1 or later; that expression won't work with older versions of libpcap or WinPcap, so, on Windows, upgrade to WinPcap 3.1 or later and, on UN*X, upgrade to libpcap 0.9.x if possible and, if not possible and you have a version of libpcap prior to 0.8.1, use

     (tcp[0:2] >= 6881 and tcp[0:2] <= 6889) or (tcp[2:2] >= 6881 and tcp[2:2] <= 6889) 
    (a bug in the libpcap optimizer in libpcap 0.8.x means this won't work with libpcap 0.8.x, although you might be able to use tcpdump with the "-O" flag).

BitTorrent (last edited 2019-03-18 22:16:09 by JimDeLaHunt)