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Timestamp:
02/04/2008 05:52:40 PM (10 months ago)
Author:
dave
Message:

modify docutils beps.py to use pep_base_url.

I tried using bep_base_url to disambiguate the base URL for beps and peps, but this required reaching
into the source code for restructured text (which has some hard-coded notion of PEPs). I decided
not to touch that code just now.

regenerate updated html files.

Files:
1 modified

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Removed

  • dotorg/trunk_fixed/html/beps/bep_0003.html

    r10492 r10535  
    22<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
    33<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 
    4 <!-- 
    5 This HTML is auto-generated.  DO NOT EDIT THIS FILE!  If you are writing a new 
    6 BEP, see http://www.bittorrent.org/beps/bep_0001.html for instructions and links 
    7 to templates.  DO NOT USE THIS HTML FILE AS YOUR TEMPLATE! 
    8 --> 
    94<head> 
    10   <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
    11   <meta name="generator" content="Docutils 0.5: http://docutils.sourceforge.net/" /> 
    12   <title>BEP 3 -- Assigned Numbers</title> 
    13   <style type="text/css"> 
    14  
    15 /* 
    16 :Author: David Goodger 
    17 :Contact: goodger@python.org 
    18 :date: $Date: 2006-05-21 22:44:42 +0200 (Sun, 21 May 2006) $ 
    19 :version: $Revision: 4564 $ 
    20 :copyright: This stylesheet has been placed in the public domain. 
    21  
    22 Default cascading style sheet for the BEP HTML output of Docutils. 
    23 */ 
    24  
    25 /* "! important" is used here to override other ``margin-top`` and 
    26    ``margin-bottom`` styles that are later in the stylesheet or  
    27    more specific.  See http://www.w3.org/TR/CSS1#the-cascade */ 
    28 .first { 
    29   margin-top: 0 ! important } 
    30  
    31 .last, .with-subtitle { 
    32   margin-bottom: 0 ! important } 
    33  
    34 .hidden { 
    35   display: none } 
    36  
    37 .navigation { 
    38   width: 100% ; 
    39   background: #99ccff ; 
    40   margin-top: 0px ; 
    41   margin-bottom: 0px } 
    42  
    43 .navigation .navicon { 
    44   width: 150px ; 
    45   height: 35px } 
    46  
    47 .navigation .textlinks { 
    48   padding-left: 1em ; 
    49   text-align: left } 
    50  
    51 .navigation td, .navigation th { 
    52   padding-left: 0em ; 
    53   padding-right: 0em ; 
    54   vertical-align: middle } 
    55  
    56 .rfc2822 { 
    57   margin-top: 0.5em ; 
    58   margin-left: 0.5em ; 
    59   margin-right: 0.5em ; 
    60   margin-bottom: 0em } 
    61  
    62 .rfc2822 td { 
    63   text-align: left } 
    64  
    65 .rfc2822 th.field-name { 
    66   text-align: right ; 
    67   font-family: sans-serif ; 
    68   padding-right: 0.5em ; 
    69   font-weight: bold ; 
    70   margin-bottom: 0em } 
    71  
    72 a.toc-backref { 
    73   text-decoration: none ; 
    74   color: black } 
    75  
    76 blockquote.epigraph { 
    77   margin: 2em 5em ; } 
    78  
    79 body { 
    80   margin: 0px ; 
    81   margin-bottom: 1em ; 
    82   padding: 0px } 
    83  
    84 dl.docutils dd { 
    85   margin-bottom: 0.5em } 
    86  
    87 div.section { 
    88   margin-left: 1em ; 
    89   margin-right: 1em ; 
    90   margin-bottom: 1.5em } 
    91  
    92 div.section div.section { 
    93   margin-left: 0em ; 
    94   margin-right: 0em ; 
    95   margin-top: 1.5em } 
    96  
    97 div.abstract { 
    98   margin: 2em 5em } 
    99  
    100 div.abstract p.topic-title { 
    101   font-weight: bold ; 
    102   text-align: center } 
    103  
    104 div.admonition, div.attention, div.caution, div.danger, div.error, 
    105 div.hint, div.important, div.note, div.tip, div.warning { 
    106   margin: 2em ; 
    107   border: medium outset ; 
    108   padding: 1em } 
    109  
    110 div.admonition p.admonition-title, div.hint p.admonition-title, 
    111 div.important p.admonition-title, div.note p.admonition-title, 
    112 div.tip p.admonition-title { 
    113   font-weight: bold ; 
    114   font-family: sans-serif } 
    115  
    116 div.attention p.admonition-title, div.caution p.admonition-title, 
    117 div.danger p.admonition-title, div.error p.admonition-title, 
    118 div.warning p.admonition-title { 
    119   color: red ; 
    120   font-weight: bold ; 
    121   font-family: sans-serif } 
    122  
    123 /* Uncomment (and remove this text!) to get reduced vertical space in 
    124    compound paragraphs. 
    125 div.compound .compound-first, div.compound .compound-middle { 
    126   margin-bottom: 0.5em } 
    127  
    128 div.compound .compound-last, div.compound .compound-middle { 
    129   margin-top: 0.5em } 
    130 */ 
    131  
    132 div.dedication { 
    133   margin: 2em 5em ; 
    134   text-align: center ; 
    135   font-style: italic } 
    136  
    137 div.dedication p.topic-title { 
    138   font-weight: bold ; 
    139   font-style: normal } 
    140  
    141 div.figure { 
    142   margin-left: 2em ; 
    143   margin-right: 2em } 
    144  
    145 div.footer, div.header { 
    146   clear: both; 
    147   font-size: smaller } 
    148  
    149 div.footer { 
    150   margin-left: 1em ; 
    151   margin-right: 1em } 
    152  
    153 div.line-block { 
    154   display: block ; 
    155   margin-top: 1em ; 
    156   margin-bottom: 1em } 
    157  
    158 div.line-block div.line-block { 
    159   margin-top: 0 ; 
    160   margin-bottom: 0 ; 
    161   margin-left: 1.5em } 
    162  
    163 div.sidebar { 
    164   margin-left: 1em ; 
    165   border: medium outset ; 
    166   padding: 1em ; 
    167   background-color: #ffffee ; 
    168   width: 40% ; 
    169   float: right ; 
    170   clear: right } 
    171  
    172 div.sidebar p.rubric { 
    173   font-family: sans-serif ; 
    174   font-size: medium } 
    175  
    176 div.system-messages { 
    177   margin: 5em } 
    178  
    179 div.system-messages h1 { 
    180   color: red } 
    181  
    182 div.system-message { 
    183   border: medium outset ; 
    184   padding: 1em } 
    185  
    186 div.system-message p.system-message-title { 
    187   color: red ; 
    188   font-weight: bold } 
    189  
    190 div.topic { 
    191   margin: 2em } 
    192  
    193 h1.section-subtitle, h2.section-subtitle, h3.section-subtitle, 
    194 h4.section-subtitle, h5.section-subtitle, h6.section-subtitle { 
    195   margin-top: 0.4em } 
    196  
    197 h1 { 
    198   font-family: sans-serif ; 
    199   font-size: large } 
    200  
    201 h2 { 
    202   font-family: sans-serif ; 
    203   font-size: medium } 
    204  
    205 h3 { 
    206   font-family: sans-serif ; 
    207   font-size: small } 
    208  
    209 h4 { 
    210   font-family: sans-serif ; 
    211   font-style: italic ; 
    212   font-size: small } 
    213  
    214 h5 { 
    215   font-family: sans-serif; 
    216   font-size: x-small } 
    217  
    218 h6 { 
    219   font-family: sans-serif; 
    220   font-style: italic ; 
    221   font-size: x-small } 
    222  
    223 hr.docutils { 
    224   width: 75% } 
    225  
    226 img.align-left { 
    227   clear: left } 
    228  
    229 img.align-right { 
    230   clear: right } 
    231  
    232 img.borderless { 
    233   border: 0 } 
    234  
    235 ol.simple, ul.simple { 
    236   margin-bottom: 1em } 
    237  
    238 ol.arabic { 
    239   list-style: decimal } 
    240  
    241 ol.loweralpha { 
    242   list-style: lower-alpha } 
    243  
    244 ol.upperalpha { 
    245   list-style: upper-alpha } 
    246  
    247 ol.lowerroman { 
    248   list-style: lower-roman } 
    249  
    250 ol.upperroman { 
    251   list-style: upper-roman } 
    252  
    253 p.attribution { 
    254   text-align: right ; 
    255   margin-left: 50% } 
    256  
    257 p.caption { 
    258   font-style: italic } 
    259  
    260 p.credits { 
    261   font-style: italic ; 
    262   font-size: smaller } 
    263  
    264 p.label { 
    265   white-space: nowrap } 
    266  
    267 p.rubric { 
    268   font-weight: bold ; 
    269   font-size: larger ; 
    270   color: maroon ; 
    271   text-align: center } 
    272  
    273 p.sidebar-title { 
    274   font-family: sans-serif ; 
    275   font-weight: bold ; 
    276   font-size: larger } 
    277  
    278 p.sidebar-subtitle { 
    279   font-family: sans-serif ; 
    280   font-weight: bold } 
    281  
    282 p.topic-title { 
    283   font-family: sans-serif ; 
    284   font-weight: bold } 
    285  
    286 pre.address { 
    287   margin-bottom: 0 ; 
    288   margin-top: 0 ; 
    289   font-family: serif ; 
    290   font-size: 100% } 
    291  
    292 pre.literal-block, pre.doctest-block { 
    293   margin-left: 2em ; 
    294   margin-right: 2em } 
    295  
    296 span.classifier { 
    297   font-family: sans-serif ; 
    298   font-style: oblique } 
    299  
    300 span.classifier-delimiter { 
    301   font-family: sans-serif ; 
    302   font-weight: bold } 
    303  
    304 span.interpreted { 
    305   font-family: sans-serif } 
    306  
    307 span.option { 
    308   white-space: nowrap } 
    309  
    310 span.option-argument { 
    311   font-style: italic } 
    312  
    313 span.pre { 
    314   white-space: pre } 
    315  
    316 span.problematic { 
    317   color: red } 
    318  
    319 span.section-subtitle { 
    320   /* font-size relative to parent (h1..h6 element) */ 
    321   font-size: 80% } 
    322  
    323 table.citation { 
    324   border-left: solid 1px gray; 
    325   margin-left: 1px } 
    326  
    327 table.docinfo { 
    328   margin: 2em 4em } 
    329  
    330 table.docutils { 
    331   margin-top: 0.5em ; 
    332   margin-bottom: 0.5em } 
    333  
    334 table.footnote { 
    335   border-left: solid 1px black; 
    336   margin-left: 1px } 
    337  
    338 table.docutils td, table.docutils th, 
    339 table.docinfo td, table.docinfo th { 
    340   padding-left: 0.5em ; 
    341   padding-right: 0.5em ; 
    342   vertical-align: top } 
    343  
    344 td.num { 
    345   text-align: right } 
    346  
    347 th.field-name { 
    348   font-weight: bold ; 
    349   text-align: left ; 
    350   white-space: nowrap ; 
    351   padding-left: 0 } 
    352  
    353 h1 tt.docutils, h2 tt.docutils, h3 tt.docutils, 
    354 h4 tt.docutils, h5 tt.docutils, h6 tt.docutils { 
    355   font-size: 100% } 
    356  
    357 ul.auto-toc { 
    358   list-style-type: none } 
    359  
    360 </style> 
     5<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
     6<meta name="generator" content="Docutils 0.5: http://docutils.sourceforge.net/" /> 
     7<title></title> 
     8<link rel="stylesheet" href="../css/bep.css" type="text/css" /> 
    3619</head> 
    362 <body bgcolor="white"> 
    363 <table class="navigation" cellpadding="0" cellspacing="0" 
    364        width="100%" border="0"> 
    365 <tr><td class="navicon" width="150" height="35"> 
    366 <!--<a href="http://www.python.org/" title="Python Home Page"> 
    367 <img src="http://www.python.org/pics/PyBanner007.gif" alt="[Python]" 
    368  border="0" width="150" height="35" /></a></td> 
    369 <td class="textlinks" align="left"> 
    370 [<b><a href="http://www.bittorrent.org/">bittorrent.org</a></b>]--> 
    371 [<b><a href="http://www.bittorrent.org/beps/">BEP Index</a></b>] 
    372 [<b><a href="./bep-0003.txt">BEP Source</a></b>] 
    373 </td></tr></table> 
     10<body> 
    37411<div class="document"> 
     12 
     13<div id="upper" class="clear"> 
     14<div id="wrap"> 
     15<div id="header"> 
     16<h1><a href="../index.html">BitTorrent<span>.org</span></a></h1> 
     17</div> 
     18<div id="nav"> 
     19<ul> 
     20<li><a href="../index.html">Home</a></li> 
     21<li><a href="../introduction.html">For Users</a></li> 
     22<li><span>For Developers</span></li> 
     23<!-- <li><a href="./blog">Blog</a></li> --> 
     24<li><a href="../donate.html">Donate!</a></li> 
     25</ul> 
     26</div> <!-- nav --> 
     27<!-- ### Begin Content ### --> 
     28<div id="second"> 
     29 
     30 
     31 
    37532<table class="rfc2822 docutils field-list" frame="void" rules="none"> 
    37633<col class="field-name" /> 
    … …  
    37936<tr class="field"><th class="field-name">BEP:</th><td class="field-body">3</td> 
    38037</tr> 
    381 <tr class="field"><th class="field-name">Title:</th><td class="field-body">Assigned Numbers</td> 
    382 </tr> 
    383 <tr class="field"><th class="field-name">Version:</th><td class="field-body">1</td> 
    384 </tr> 
    385 <tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="https://svn.bittorrent.com/trac.cgi/browser/dotorg/trunk/html/beps/bep_0003.rst">31-Jan-2008</a></td> 
    386 </tr> 
    387 <tr class="field"><th class="field-name">Author:</th><td class="field-body">David Harrison</td> 
    388 </tr> 
    389 <tr class="field"><th class="field-name">Status:</th><td class="field-body">Active</td> 
    390 </tr> 
    391 <tr class="field"><th class="field-name">Type:</th><td class="field-body">Process</td> 
     38<tr class="field"><th class="field-name">Title:</th><td class="field-body">The BitTorrent Protocol Specification</td> 
     39</tr> 
     40<tr class="field"><th class="field-name">Version:</th><td class="field-body">$Revision$</td> 
     41</tr> 
     42<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="https://svn.bittorrent.com/trac.cgi/browser/dotorg/trunk/html/beps/bep_0003.rst">$Date$</a></td> 
     43</tr> 
     44<tr class="field"><th class="field-name">Author:</th><td class="field-body">Bram Cohen &lt;bram&#32;&#97;t&#32;bittorrent.com&gt;</td> 
     45</tr> 
     46<tr class="field"><th class="field-name">Status:</th><td class="field-body">Final</td> 
     47</tr> 
     48<tr class="field"><th class="field-name">Type:</th><td class="field-body">Standard</td> 
    39249</tr> 
    39350<tr class="field"><th class="field-name">Created:</th><td class="field-body">10-Jan-2008</td> 
    … …  
    40158<p class="topic-title first">Contents</p> 
    40259<ul class="simple"> 
    403 <li><a class="reference internal" href="#bittorrent-org-for-developers-assigned-numbers" id="id2">BitTorrent.org » For Developers » Assigned Numbers</a><ul> 
    404 <li><a class="reference internal" href="#reserved-bit-allocations" id="id3">Reserved Bit Allocations</a></li> 
    405 <li><a class="reference internal" href="#reserved-message-ids" id="id4">Reserved Message IDs</a></li> 
    406 </ul> 
    407 </li> 
    408 </ul> 
    409 </div> 
    410 <div class="section" id="bittorrent-org-for-developers-assigned-numbers"> 
    411 <h1><a class="toc-backref" href="#id2">BitTorrent.org » For Developers » Assigned Numbers</a></h1> 
    412 <p>This document describes the known bit allocations and message IDs for 
    413 the BitTorrent protocol.  To request a bit allocation contact 
    414 <a class="reference external" href="mailto:editor&#64;bittorrent.org">editor&#64;bittorrent.org</a>.  Contact the same address if you are aware of 
    415 any omissions.</p> 
    416 <div class="section" id="reserved-bit-allocations"> 
    417 <h2><a class="toc-backref" href="#id3">Reserved Bit Allocations</a></h2> 
    418 <pre class="literal-block"> 
    419 reserved[0] 
    420 0x80  Azureus Messaging Protocol 
    421  
    422 reserved[5] 
    423 0x10  LTEP (LibTorrent Extension Protocol) 
    424  
    425 reserved[7] 
    426 0x01  BitTorrent DHT 
    427 0x04  suggest, haveall, havenone, reject request, and allow fast extensions 
    428 </pre> 
    429 </div> 
    430 <div class="section" id="reserved-message-ids"> 
    431 <h2><a class="toc-backref" href="#id4">Reserved Message IDs</a></h2> 
    432 <pre class="literal-block"> 
    433 Core Protocol: 
    434 0x00   choke 
    435 0x01   unchoke 
    436 0x02   interested 
    437 0x03   not interested 
    438 0x04   have 
    439 0x05   bitfield 
    440 0x06   request 
    441 0x07   piece 
    442 0x08   cancel 
    443 0x09   port 
    444  
    445 Fast Extensions 
    446  
    447 0x0D   suggest 
    448 0x0E   have all 
    449 0x0F   have none 
    450 0x10   reject request 
    451 0x11   allowed fast 
    452  
    453 Additional IDs used in deployed clients 
    454 0x14   LTEP Handshake (implemented in libtorrent, uTorrent,...) 
    455 </pre> 
    456 </div> 
     60<li><a class="reference internal" href="#a-bittorrent-file-distribution-consists-of-these-entities" id="id2">A BitTorrent file distribution consists of these entities:</a></li> 
     61<li><a class="reference internal" href="#to-start-serving-a-host-goes-through-the-following-steps" id="id3">To start serving, a host goes through the following steps:</a></li> 
     62<li><a class="reference internal" href="#to-start-downloading-a-user-does-the-following" id="id4">To start downloading, a user does the following:</a></li> 
     63<li><a class="reference internal" href="#the-connectivity-is-as-follows" id="id5">The connectivity is as follows:</a></li> 
     64<li><a class="reference internal" href="#metainfo-files-are-bencoded-dictionaries-with-the-following-keys" id="id6">Metainfo files are bencoded dictionaries with the following keys:</a></li> 
     65<li><a class="reference internal" href="#tracker-get-requests-have-the-following-keys" id="id7">Tracker GET requests have the following keys:</a></li> 
     66<li><a class="reference internal" href="#all-non-keepalive-messages-start-with-a-single-byte-which-gives-their-type" id="id8">All non-keepalive messages start with a single byte which gives their type.</a></li> 
     67<li><a class="reference internal" href="#the-possible-values-are" id="id9">The possible values are:</a></li> 
     68</ul> 
     69</div> 
     70<p>BitTorrent is a protocol for distributing files. It identifies content 
     71by URL and is designed to integrate seamlessly with the web. Its 
     72advantage over plain HTTP is that when multiple downloads of the same 
     73file happen concurrently, the downloaders upload to each other, making 
     74it possible for the file source to support very large numbers of 
     75downloaders with only a modest increase in its load.</p> 
     76<div class="section" id="a-bittorrent-file-distribution-consists-of-these-entities"> 
     77<h1>A BitTorrent file distribution consists of these entities:</h1> 
     78<ul class="simple"> 
     79<li>An ordinary web server</li> 
     80<li>A static 'metainfo' file</li> 
     81<li>A BitTorrent tracker</li> 
     82<li>An 'original' downloader</li> 
     83<li>The end user web browsers</li> 
     84<li>The end user downloaders</li> 
     85</ul> 
     86<p>There are ideally many end users for a single file.</p> 
     87</div> 
     88<div class="section" id="to-start-serving-a-host-goes-through-the-following-steps"> 
     89<h1>To start serving, a host goes through the following steps:</h1> 
     90<ol class="arabic simple"> 
     91<li>Start running a tracker (or, more likely, have one running already).</li> 
     92<li>Start running an ordinary web server, such as apache, or have one already.</li> 
     93<li>Associate the extension .torrent with mimetype application/x-bittorrent on their web server (or have done so already).</li> 
     94<li>Generate a metainfo (.torrent) file using the complete file to be served and the URL of the tracker.</li> 
     95<li>Put the metainfo file on the web server.</li> 
     96<li>Link to the metainfo (.torrent) file from some other web page.</li> 
     97<li>Start a downloader which already has the complete file (the 'origin').</li> 
     98</ol> 
     99</div> 
     100<div class="section" id="to-start-downloading-a-user-does-the-following"> 
     101<h1>To start downloading, a user does the following:</h1> 
     102<ol class="arabic simple"> 
     103<li>Install BitTorrent (or have done so already).</li> 
     104<li>Surf the web.</li> 
     105<li>Click on a link to a .torrent file.</li> 
     106<li>Select where to save the file locally, or select a partial download to resume.</li> 
     107<li>Wait for download to complete.</li> 
     108<li>Tell downloader to exit (it keeps uploading until this happens).</li> 
     109</ol> 
     110</div> 
     111<div class="section" id="the-connectivity-is-as-follows"> 
     112<h1>The connectivity is as follows:</h1> 
     113<ul class="simple"> 
     114<li>Strings are length-prefixed base ten followed by a colon and the string. For example <tt class="docutils literal"><span class="pre">4:spam</span></tt> corresponds to 'spam'.</li> 
     115<li>Integers are represented by an 'i' followed by the number in base 10 
     116followed by an 'e'. For example <tt class="docutils literal"><span class="pre">i3e</span></tt> corresponds to 3 and 
     117<tt class="docutils literal"><span class="pre">i-3e</span></tt> corresponds to -3. Integers have no size 
     118limitation. <tt class="docutils literal"><span class="pre">i-0e</span></tt> is invalid. All encodings with a leading 
     119zero, such as <tt class="docutils literal"><span class="pre">i03e</span></tt>, are invalid, other than 
     120<tt class="docutils literal"><span class="pre">i0e</span></tt>, which of course corresponds to 0.</li> 
     121<li>Lists are encoded as an 'l' followed by their elements (also 
     122bencoded) followed by an 'e'. For example <tt class="docutils literal"><span class="pre">l4:spam4:eggse</span></tt> 
     123corresponds to ['spam', 'eggs'].</li> 
     124<li>Dictionaries are encoded as a 'd' followed by a list of alternating 
     125keys and their corresponding values followed by an 'e'. For example, 
     126<tt class="docutils literal"><span class="pre">d3:cow3:moo4:spam4:eggse</span></tt> corresponds to {'cow': 'moo', 
     127'spam': 'eggs'} and <tt class="docutils literal"><span class="pre">d4:spaml1:a1:bee</span></tt> corresponds to 
     128{'spam': ['a', 'b']}. Keys must be strings and appear in sorted order 
     129(sorted as raw strings, not alphanumerics).</li> 
     130</ul> 
     131</div> 
     132<div class="section" id="metainfo-files-are-bencoded-dictionaries-with-the-following-keys"> 
     133<h1>Metainfo files are bencoded dictionaries with the following keys:</h1> 
     134<dl class="docutils"> 
     135<dt>announce</dt> 
     136<dd>The URL of the tracker.</dd> 
     137<dt>info</dt> 
     138<dd><p class="first">This maps to a dictionary, with keys described below.</p> 
     139<p>The <tt class="docutils literal"><span class="pre">name</span></tt> key maps to a string which is the suggested name 
     140to save the file (or directory) as. It is purely advisory.</p> 
     141<p><tt class="docutils literal"><span class="pre">piece</span> <span class="pre">length</span></tt> maps to the number of bytes in each piece 
     142the file is split into. For the purposes of transfer, files are 
     143split into fixed-size pieces which are all the same length except for 
     144possibly the last one which may be truncated. <tt class="docutils literal"><span class="pre">piece</span> 
     145<span class="pre">length</span></tt> is almost always a power of two, most commonly 2 18 = 
     146256 K (BitTorrent prior to version 3.2 uses 2 20 = 1 M as 
     147default).</p> 
     148<p><tt class="docutils literal"><span class="pre">pieces</span></tt> maps to a string whose length is a multiple of 
     14920. It is to be subdivided into strings of length 20, each of which is 
     150the SHA1 hash of the piece at the corresponding index.</p> 
     151<p>There is also a key <tt class="docutils literal"><span class="pre">length</span></tt> or a key <tt class="docutils literal"><span class="pre">files</span></tt>, 
     152but not both or neither. If <tt class="docutils literal"><span class="pre">length</span></tt> is present then the 
     153download represents a single file, otherwise it represents a set of 
     154files which go in a directory structure.</p> 
     155<p>In the single file case, <tt class="docutils literal"><span class="pre">length</span></tt> maps to the length of 
     156the file in bytes.</p> 
     157<p>For the purposes of the other keys, the multi-file case is treated as 
     158only having a single file by concatenating the files in the order they 
     159appear in the files list. The files list is the value 
     160<tt class="docutils literal"><span class="pre">files</span></tt> maps to, and is a list of dictionaries containing 
     161the following keys:</p> 
     162<p><tt class="docutils literal"><span class="pre">length</span></tt> - The length of the file, in bytes.</p> 
     163<p><tt class="docutils literal"><span class="pre">path</span></tt> - A list of strings corresponding to subdirectory 
     164names, the last of which is the actual file name (a zero length list 
     165is an error case).</p> 
     166<p class="last">In the single file case, the name key is the name of a file, in the 
     167muliple file case, it's the name of a directory.</p> 
     168</dd> 
     169</dl> 
     170</div> 
     171<div class="section" id="tracker-get-requests-have-the-following-keys"> 
     172<h1>Tracker GET requests have the following keys:</h1> 
     173<dl class="docutils"> 
     174<dt>info_hash</dt> 
     175<dd>The 20 byte sha1 hash of the bencoded form of the info value from the 
     176metainfo file. Note that this is a substring of the metainfo 
     177file. This value will almost certainly have to be escaped.</dd> 
     178<dt>peer_id</dt> 
     179<dd>A string of length 20 which this downloader uses as its id. Each 
     180downloader generates its own id at random at the start of a new 
     181download. This value will also almost certainly have to be escaped.</dd> 
     182<dt>ip</dt> 
     183<dd>An optional parameter giving the IP (or dns name) which this peer is 
     184at. Generally used for the origin if it's on the same machine as the 
     185tracker.</dd> 
     186<dt>port</dt> 
     187<dd>The port number this peer is listening on. Common behavior is for a 
     188downloader to try to listen on port 6881 and if that port is taken try 
     1896882, then 6883, etc. and give up after 6889.</dd> 
     190<dt>uploaded</dt> 
     191<dd>The total amount uploaded so far, encoded in base ten ascii.</dd> 
     192<dt>downloaded</dt> 
     193<dd>The total amount downloaded so far, encoded in base ten ascii.</dd> 
     194<dt>left</dt> 
     195<dd>The number of bytes this peer still has to download, encoded in 
     196base ten ascii. Note that this can't be computed from downloaded and 
     197the file length since it might be a resume, and there's a chance that 
     198some of the downloaded data failed an integrity check and had to be 
     199re-downloaded.</dd> 
     200<dt>event</dt> 
     201<dd>This is an optional key which maps to <tt class="docutils literal"><span class="pre">started</span></tt>, 
     202<tt class="docutils literal"><span class="pre">completed</span></tt>, or <tt class="docutils literal"><span class="pre">stopped</span></tt> (or 
     203<tt class="docutils literal"><span class="pre">empty</span></tt>, which is the same as not being present). If not 
     204present, this is one of the announcements done at regular 
     205intervals. An announcement using <tt class="docutils literal"><span class="pre">started</span></tt> is sent when a 
     206download first begins, and one using <tt class="docutils literal"><span class="pre">completed</span></tt> is sent 
     207when the download is complete. No <tt class="docutils literal"><span class="pre">completed</span></tt> is sent if 
     208the file was complete when started. Downloaders send an announcement 
     209using <tt class="docutils literal"><span class="pre">stopped</span></tt> when they cease downloading.</dd> 
     210</dl> 
     211<p>Tracker responses are bencoded dictionaries. If a tracker response 
     212has a key <tt class="docutils literal"><span class="pre">failure</span> <span class="pre">reason</span></tt>, then that maps to a human 
     213readable string which explains why the query failed, and no other keys 
     214are required. Otherwise, it must have two keys: <tt class="docutils literal"><span class="pre">interval</span></tt>, 
     215which maps to the number of seconds the downloader should wait between 
     216regular rerequests, and <tt class="docutils literal"><span class="pre">peers</span></tt>. <tt class="docutils literal"><span class="pre">peers</span></tt> maps to 
     217a list of dictionaries corresponding to <tt class="docutils literal"><span class="pre">peers</span></tt>, each of 
     218which contains the keys <tt class="docutils literal"><span class="pre">peer</span> <span class="pre">id</span></tt>, <tt class="docutils literal"><span class="pre">ip</span></tt>, and 
     219<tt class="docutils literal"><span class="pre">port</span></tt>, which map to the peer's self-selected ID, IP 
     220address or dns name as a string, and port number, respectively. Note 
     221that downloaders may rerequest on nonscheduled times if an event 
     222happens or they need more peers.</p> 
     223<p>If you want to make any extensions to metainfo files or tracker 
     224queries, please coordinate with Bram Cohen to make sure that all 
     225extensions are done compatibly.</p> 
     226<p>BitTorrent's peer protocol operates over TCP. It performs efficiently 
     227without setting any socket options.</p> 
     228<p>Peer connections are symmetrical. Messages sent in both directions 
     229look the same, and data can flow in either direction.</p> 
     230<p>The peer protocol refers to pieces of the file by index as 
     231described in the metainfo file, starting at zero. When a peer finishes 
     232downloading a piece and checks that the hash matches, it announces 
     233that it has that piece to all of its peers.</p> 
     234<p>Connections contain two bits of state on either end: choked or not, 
     235and interested or not. Choking is a notification that no data will be 
     236sent until unchoking happens. The reasoning and common techniques 
     237behind choking are explained later in this document.</p> 
     238<p>Data transfer takes place whenever one side is interested and the 
     239other side is not choking. Interest state must be kept up to date at 
     240all times - whenever a downloader doesn't have something they 
     241currently would ask a peer for in unchoked, they must express lack of 
     242interest, despite being choked. Implementing this properly is tricky, 
     243but makes it possible for downloaders to know which peers will start 
     244downloading immediately if unchoked.</p> 
     245<p>Connections start out choked and not interested.</p> 
     246<p>When data is being transferred, downloaders should keep several 
     247piece requests queued up at once in order to get good TCP performance 
     248(this is called 'pipelining'.) On the other side, requests which can't 
     249be written out to the TCP buffer immediately should be queued up in 
     250memory rather than kept in an application-level network buffer, so 
     251they can all be thrown out when a choke happens.</p> 
     252<p>The peer wire protocol consists of a handshake followed by a 
     253never-ending stream of length-prefixed messages. The handshake starts 
     254with character ninteen (decimal) followed by the string 'BitTorrent 
     255protocol'. The leading character is a length prefix, put there in the 
     256hope that other new protocols may do the same and thus be trivially 
     257distinguishable from each other.</p> 
     258<p>All later integers sent in the protocol are encoded as four bytes 
     259big-endian.</p> 
     260<p>After the fixed headers come eight reserved bytes, which are all 
     261zero in all current implementations. If you wish to extend the 
     262protocol using these bytes, please coordinate with Bram Cohen to make 
     263sure all extensions are done compatibly.</p> 
     264<p>Next comes the 20 byte sha1 hash of the bencoded form of the info 
     265value from the metainfo file. (This is the same value which is 
     266announced as <tt class="docutils literal"><span class="pre">info_hash</span></tt> to the tracker, only here it's raw 
     267instead of quoted here). If both sides don't send the same value, they 
     268sever the connection. The one possible exception is if a downloader 
     269wants to do multiple downloads over a single port, they may wait for 
     270incoming connections to give a download hash first, and respond with 
     271the same one if it's in their list.</p> 
     272<p>After the download hash comes the 20-byte peer id which is reported 
     273in tracker requests and contained in peer lists in tracker 
     274responses. If the receiving side's peer id doesn't match the one the 
     275initiating side expects, it severs the connection.</p> 
     276<p>That's it for handshaking, next comes an alternating stream of 
     277length prefixes and messages. Messages of length zero are keepalives, 
     278and ignored. Keepalives are generally sent once every two minutes, but 
     279note that timeouts can be done much more quickly when data is 
     280expected.</p> 
     281</div> 
     282<div class="section" id="all-non-keepalive-messages-start-with-a-single-byte-which-gives-their-type"> 
     283<h1>All non-keepalive messages start with a single byte which gives their type.</h1> 
     284</div> 
     285<div class="section" id="the-possible-values-are"> 
     286<h1>The possible values are:</h1> 
     287<ul class="simple"> 
     288<li>0 - choke</li> 
     289<li>1 - unchoke</li> 
     290<li>2 - interested</li> 
     291<li>3 - not interested</li> 
     292<li>4 - have</li> 
     293<li>5 - bitfield</li> 
     294<li>6 - request</li> 
     295<li>7 - piece</li> 
     296<li>8 - cancel</li> 
     297</ul> 
     298<p>'choke', 'unchoke', 'interested', and 'not interested' have no payload.</p> 
     299<p>'bitfield' is only ever sent as the first message. Its payload is a 
     300bitfield with each index that downloader has sent set to one and the 
     301rest set to zero. Downloaders which don't have anything yet may skip 
     302the 'bitfield' message. The first byte of the bitfield corresponds to 
     303indices 0 - 7 from high bit to low bit, respectively. The next one 
     3048-15, etc. Spare bits at the end are set to zero.</p> 
     305<p>The 'have' message's payload is a single number, the index which 
     306that downloader just completed and checked the hash of.</p> 
     307<p>'request' messages contain an index, begin, and length. The last 
     308two are byte offsets. Length is generally a power of two unless it 
     309gets truncated by the end of the file. All current implementations use 
     3102 15 , and close connections which request an amount greater than 2 
     31117.</p> 
     312<p>'cancel' messages have the same payload as request messages. They 
     313are generally only sent towards the end of a download, during what's 
     314called 'endgame mode'. When a download is almost complete, there's a 
     315tendency for the last few pieces to all be downloaded off a single 
     316hosed modem line, taking a very long time. To make sure the last few 
     317pieces come in quickly, once requests for all pieces a given 
     318downloader doesn't have yet are currently pending, it sends requests 
     319for everything to everyone it's downloading from. To keep this from 
     320becoming horribly inefficient, it sends cancels to everyone else every 
     321time a piece arrives.</p> 
     322<p>'piece' messages contain an index, begin, and piece. Note that they 
     323are correlated with request messages implicitly. It's possible for an 
     324unexpected piece to arrive if choke and unchoke messages are sent in 
     325quick succession and/or transfer is going very slowly.</p> 
     326<p>Downloaders generally download pieces in random order, which does a 
     327reasonably good job of keeping them from having a strict subset or 
     328superset of the pieces of any of their peers.</p> 
     329<p>Choking is done for several reasons. TCP congestion control behaves 
     330very poorly when sending over many connections at once. Also, choking 
     331lets each peer use a tit-for-tat-ish algorithm to ensure that they get 
     332a consistent download rate.</p> 
     333<p>The choking algorithm described below is the currently deployed 
     334one. It is very important that all new algorithms work well both in a