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33<table class="rfc2822 docutils field-list" frame="void" rules="none">
34<col class="field-name" />
35<col class="field-body" />
36<tbody valign="top">
37<tr class="field"><th class="field-name">BEP:</th><td class="field-body">20</td>
38</tr>
39<tr class="field"><th class="field-name">Title:</th><td class="field-body">Peer ID Conventions</td>
40</tr>
41<tr class="field"><th class="field-name">Version:</th><td class="field-body">11031</td>
42</tr>
43<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://svn.bittorrent.org/trac/browser/dotorg/trunk/html/beps/bep_0020.rst">2008-02-28 16:43:58 -0800 (Thu, 28 Feb 2008)</a></td>
44</tr>
45<tr class="field"><th class="field-name">Author:</th><td class="field-body">David Harrison &lt;dave&#32;&#97;t&#32;bittorrent.com&gt;</td>
46</tr>
47<tr class="field"><th class="field-name">Status:</th><td class="field-body">Active</td>
48</tr>
49<tr class="field"><th class="field-name">Type:</th><td class="field-body">Process</td>
50</tr>
51<tr class="field"><th class="field-name">Created:</th><td class="field-body">Feb-27-2008</td>
52</tr>
53<tr class="field"><th class="field-name">Post-History:</th><td class="field-body"></td>
54</tr>
55</tbody>
56</table>
57<hr />
58<div class="contents topic" id="contents">
59<p class="topic-title first">Contents</p>
60<ul class="simple">
61<li><a class="reference internal" href="#references" id="id3">References</a></li>
62<li><a class="reference internal" href="#copyright" id="id4">Copyright</a></li>
63</ul>
64</div>
65<p>The 20-byte <em>peer id</em> field sent in tracker requests and in the peer
66handshake has traditionally been used not only to identify peers but
67also to identify the client implementation and version.</p>
68<p>The mainline client sets the first character in the peer-id to <tt class="docutils literal"><span class="pre">M</span></tt>
69followed by version number represented by ascii digits with major,
70minor and tiny versions separated by dashes.  Examples include
71<tt class="docutils literal"><span class="pre">M4-3-6--</span></tt> or <tt class="docutils literal"><span class="pre">M4-20-8-</span></tt> for versions 4.3.6 and 4.20.8.  The remaining
72bytes in the peer id are random.  The following list was originally
73derived from <a class="footnote-reference" href="#theory" id="id1">[1]</a>.</p>
74<p>A number of clients begin the peer id with a dash followed by two
75characters to identify the client implementation, four ascii digits to
76denote version number, and a dash.  As with mainline, the remaining
77bytes are random.  An example is <tt class="docutils literal"><span class="pre">-AZ2060-</span></tt>.</p>
78<p>Known clients that use this encoding style are</p>
79<pre class="literal-block">
80'AG' - Ares
81'A~' - Ares
82'AR' - Arctic
83'AV' - Avicora
84'AX' - BitPump
85'AZ' - Azureus
86'BB' - BitBuddy
87'BC' - BitComet
88'BF' - Bitflu
89'BG' - BTG (uses Rasterbar libtorrent)
90'BR' - BitRocket
91'BS' - BTSlave
92'BX' - ~Bittorrent X
93'CD' - Enhanced CTorrent
94'CT' - CTorrent
95'DE' - DelugeTorrent
96'DP' - Propagate Data Client
97'EB' - EBit
98'ES' - electric sheep
99'FT' - FoxTorrent
100'GS' - GSTorrent
101'HL' - Halite
102'HN' - Hydranode
103'KG' - KGet
104'KT' - KTorrent
105'LH' - LH-ABC
106'LP' - Lphant
107'LT' - libtorrent
108'lt' - libTorrent
109'LW' - LimeWire
110'MO' - MonoTorrent
111'MP' - MooPolice
112'MR' - Miro
113'MT' - MoonlightTorrent
114'NX' - Net Transport
115'PD' - Pando
116'qB' - qBittorrent
117'QD' - QQDownload
118'QT' - Qt 4 Torrent example
119'RT' - Retriever
120'S~' - Shareaza alpha/beta
121'SB' - ~Swiftbit
122'SS' - SwarmScope
123'ST' - SymTorrent
124'st' - sharktorrent
125'SZ' - Shareaza
126'TN' - TorrentDotNET
127'TR' - Transmission
128'TS' - Torrentstorm
129'TT' - TuoTu
130'UL' - uLeecher!
131'UT' - µTorrent
132'VG' - Vagaa
133'WT' - BitLet
134'WY' - FireTorrent
135'XL' - Xunlei
136'XT' - XanTorrent
137'XX' - Xtorrent
138'ZT' - ZipTorrent
139</pre>
140<p>The following clients have been seen in the wild and need to be identified:</p>
141<pre class="literal-block">
142'BD' (example: -BD0300-)
143'NP' (example: -NP0201-)
144'wF' (example: -wF2200-)
145</pre>
146<p>Shad0w with his experimental BitTorrent implementation and BitTornado
147introduced peer ids that begin with a character which is``T`` in the
148case of BitTornado followed by up to five ascii characters for version
149number, padded with dashes if less than 5, followed by <tt class="docutils literal"><span class="pre">---</span></tt>.  The
150ascii characters denoting version are limited to the following
151characters:</p>
152<pre class="literal-block">
1530123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz.-
154</pre>
155<p>For example: 'S58B-----'... for Shadow's 5.8.11</p>
156<p>As with other peer id formats, the remanining bytes are random.  There
157are significant deviations from this explained here <a class="footnote-reference" href="#shad0w" id="id2">[2]</a>.</p>
158<p>Known clients that uses this encoding style are:</p>
159<pre class="literal-block">
160'A' - ABC
161'O' - Osprey Permaseed
162'Q' - BTQueue
163'R' - Tribler
164'S' - Shadow's client
165'T' - BitTornado
166'U' - UPnP NAT Bit Torrent
167</pre>
168<p>BitComet produces peer ids that consists of four ASCII characters
169<tt class="docutils literal"><span class="pre">exbc</span></tt>, followed by two bytes <em>x</em> and <em>y</em>, followed by random
170characters. The version number is <em>x</em> in decimal before the decimal
171point and <em>y</em> as two decimal digits after the decimal point. BitLord
172uses the same scheme, but adds <tt class="docutils literal"><span class="pre">LORD</span></tt> after the version bytes. An
173unofficial patch for BitComet once replaced <tt class="docutils literal"><span class="pre">exbc</span></tt> with <tt class="docutils literal"><span class="pre">FUTB</span></tt>. The
174encoding for BitComet Peer IDs changed to Azureus-style as of BitComet
175version 0.59.</p>
176<p>XBT Client has its own style too. Its peer_id consists of the three
177uppercase characters <tt class="docutils literal"><span class="pre">XBT</span></tt> followed by three ASCII digits representing
178the version number. If the client is a debug build, the seventh byte
179is the lowercase character <tt class="docutils literal"><span class="pre">d</span></tt>, otherwise it is a <tt class="docutils literal"><span class="pre">-</span></tt>. Following that
180is a <tt class="docutils literal"><span class="pre">-</span></tt> then random digits, uppercase and lowercase letters. Example:
181<tt class="docutils literal"><span class="pre">XBT054d-</span></tt> at the beginning would indicate a debug build of version
1820.5.4.</p>
183<p>Opera 8 previews and Opera 9.x releases use the following peer_id
184scheme: The first two characters are <tt class="docutils literal"><span class="pre">OP</span></tt> and the next four digits
185equal the build number. All following characters are random lowercase
186hexdecimal digits.</p>
187<p>MLdonkey use the following peer_id scheme: the first characters are
188<tt class="docutils literal"><span class="pre">-ML</span></tt> followed by a dotted version then a <tt class="docutils literal"><span class="pre">-</span></tt> followed by
189randomness. e.g. <tt class="docutils literal"><span class="pre">-ML2.7.2-kgjjfkd</span></tt></p>
190<p>Bits on Wheels uses the pattern <tt class="docutils literal"><span class="pre">-BOWxxx-yyyyyyyyyyyy</span></tt>, where y is
191random (uppercase letters) and x depends on the version. Version 1.0.6
192has xxx = A0C.</p>
193<p>Queen Bee uses Bram``s new style: <tt class="docutils literal"><span class="pre">Q1-0-0--</span></tt> or <tt class="docutils literal"><span class="pre">Q1-10-0-</span></tt> followed by
194random bytes.</p>
195<p>BitTyrant is an Azureus fork and simply uses <tt class="docutils literal"><span class="pre">AZ2500BT</span></tt> + random bytes
196as peer ID in its 1.1 version. Note the missing dashes.</p>
197<p>TorrenTopia version 1.90 pretends to be or is derived from Mainline
1983.4.6. Its peer ID starts with <tt class="docutils literal"><span class="pre">346------</span></tt>.</p>
199<p>BitSpirit has several modes for its peer ID. In one mode it reads the
200ID of its peer and reconnects using the first eight bytes as a basis
201for its own ID. Its real ID appears to use <tt class="docutils literal"><span class="pre">\\0\\3BS</span></tt> (C notation) as
202the first four bytes for version 3.x and <tt class="docutils literal"><span class="pre">\\0\\2BS</span></tt> for version 2.x. In
203all modes the ID may end in <tt class="docutils literal"><span class="pre">UDP0</span></tt>.</p>
204<p>Rufus uses its version as decimal ASCII values for the first two
205bytes. The third and fourth bytes are <tt class="docutils literal"><span class="pre">RS</span></tt>. What then follows is the
206nickname of the user and some random bytes.</p>
207<p>G3 Torrent starts its peer ID with <tt class="docutils literal"><span class="pre">-G3</span></tt> and appends up to 9
208characters of the nickname of the user.</p>
209<p>FlashGet uses Azureus style with <tt class="docutils literal"><span class="pre">FG</span></tt> but without the trailing
210<tt class="docutils literal"><span class="pre">-</span></tt>. Version 1.82.1002 still uses the version digits <tt class="docutils literal"><span class="pre">0180</span></tt>.</p>
211<p>AllPeers takes the sha1 hash of a user dependent string and replaces
212the first few characters with &quot;AP&quot; + version string + &quot;-&quot;.</p>
213<div class="section" id="references">
214<h1>References</h1>
215<table class="docutils footnote" frame="void" id="theory" rules="none">
216<colgroup><col class="label" /><col /></colgroup>
217<tbody valign="top">
218<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td><a class="reference external" href="http://wiki.theory.org/BitTorrentSpecification">http://wiki.theory.org/BitTorrentSpecification</a></td></tr>
219</tbody>
220</table>
221<table class="docutils footnote" frame="void" id="shad0w" rules="none">
222<colgroup><col class="label" /><col /></colgroup>
223<tbody valign="top">
224<tr><td class="label"><a class="fn-backref" href="#id2">[2]</a></td><td><a class="reference external" href="http://forums.degreez.net/viewtopic.php?t=7070">http://forums.degreez.net/viewtopic.php?t=7070</a></td></tr>
225</tbody>
226</table>
227</div>
228<div class="section" id="copyright">
229<h1>Copyright</h1>
230<p>This document has been placed in the public domain.</p>
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