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premiere-libtorrent/docs/udp_tracker_protocol.rst

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=========================================
Bittorrent udp-tracker protocol extension
=========================================
.. contents::
introduction
++++++++++++
A tracker with the protocol "udp://" in its URI
is supposed to be contacted using this protocol.
This protocol is supported by
xbt-tracker_.
.. _xbt-tracker: http://xbtt.sourceforge.net
For additional information and descritptions of
the terminology used in this document, see
the `protocol specification`__
__ http://wiki.theory.org/index.php/BitTorrentSpecification
All values are sent in network byte order (big endian). The sizes
are specified with ANSI-C standard types.
If no response to a request is received within 15 seconds, resend
the request. If no reply has been received after 60 seconds, stop
retrying.
connecting
++++++++++
Client sends packet:
--------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int64_t | connection_id | Must be initialized to 0x41727101980 |
| | | in network byte order. This will |
| | | identify the protocol. |
+-------------+---------------------+----------------------------------------+
| int32_t | action | 0 for a connection request |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Randomized by client. |
+-------------+---------------------+----------------------------------------+
Server replies with packet:
---------------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int32_t | action | Describes the type of packet, in this |
| | | case it should be 0, for connect. |
| | | If 3 (for error) see errors_. |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Must match the transaction_id sent |
| | | from the client. |
+-------------+---------------------+----------------------------------------+
| int64_t | connection_id | A connection id, this is used when |
| | | further information is exchanged with |
| | | the tracker, to identify you. |
| | | This connection id can be reused for |
| | | multiple requests, but if it's cached |
| | | for too long, it will not be valid |
| | | anymore. |
+-------------+---------------------+----------------------------------------+
announcing
++++++++++
Client sends packet:
--------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int64_t | connection_id | The connection id acquired from |
| | | establishing the connection. |
+-------------+---------------------+----------------------------------------+
| int32_t | action | Action. in this case, 1 for announce. |
| | | See actions_. |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Randomized by client. |
+-------------+---------------------+----------------------------------------+
| int8_t[20] | info_hash | The info-hash of the torrent you want |
| | | announce yourself in. |
+-------------+---------------------+----------------------------------------+
| int8_t[20] | peer_id | Your peer id. |
+-------------+---------------------+----------------------------------------+
| int64_t | downloaded | The number of byte you've downloaded |
| | | in this session. |
+-------------+---------------------+----------------------------------------+
| int64_t | left | The number of bytes you have left to |
| | | download until you're finished. |
+-------------+---------------------+----------------------------------------+
| int64_t | uploaded | The number of bytes you have uploaded |
| | | in this session. |
+-------------+---------------------+----------------------------------------+
| int32_t | event | The event, one of |
| | | |
| | | * none = 0 |
| | | * completed = 1 |
| | | * started = 2 |
| | | * stopped = 3 |
+-------------+---------------------+----------------------------------------+
| uint32_t | ip | Your ip address. Set to 0 if you want |
| | | the tracker to use the ``sender`` of |
| | | this udp packet. |
+-------------+---------------------+----------------------------------------+
| uint32_t | key | A unique key that is randomized by the |
| | | client. |
+-------------+---------------------+----------------------------------------+
| int32_t | num_want | The maximum number of peers you want |
| | | in the reply. Use -1 for default. |
+-------------+---------------------+----------------------------------------+
| uint16_t | port | The port you're listening on. |
+-------------+---------------------+----------------------------------------+
| uint16_t | extensions | See extensions_ |
+-------------+---------------------+----------------------------------------+
Server replies with packet:
---------------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int32_t | action | The action this is a reply to. Should |
| | | in this case be 1 for announce. |
| | | If 3 (for error) see errors_. |
| | | See actions_. |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Must match the transaction_id sent |
| | | in the announce request. |
+-------------+---------------------+----------------------------------------+
| int32_t | interval | the number of seconds you should wait |
| | | until reannouncing yourself. |
+-------------+---------------------+----------------------------------------+
| int32_t | leechers | The number of peers in the swarm that |
| | | has not finished downloading. |
+-------------+---------------------+----------------------------------------+
| int32_t | seeders | The number of peers in the swarm that |
| | | has finished downloading and are |
| | | seeding. |
+-------------+---------------------+----------------------------------------+
The rest of the server reply is a variable number of the following structure:
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int32_t | ip | The ip of a peer in the swarm. |
+-------------+---------------------+----------------------------------------+
| uint16_t | port | The peer's listen port. |
+-------------+---------------------+----------------------------------------+
scraping
++++++++
Client sends packet:
--------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int64_t | connection_id | The connection id retreived from the |
| | | establishing of the connection. |
+-------------+---------------------+----------------------------------------+
| int32_t | action | The action, in this case, 2 for |
| | | scrape. See actions_. |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Randomized by client. |
+-------------+---------------------+----------------------------------------+
| int16_t | num_info_hashes | The number of info-hashes that will |
| | | follow. |
+-------------+---------------------+----------------------------------------+
| uint16_t | extensions | See extensions_. |
+-------------+---------------------+----------------------------------------+
The following structure is repeated ``num_info_hashes`` times:
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int8_t[20] | info_hash | The info hash that is to be scraped. |
+-------------+---------------------+----------------------------------------+
Server replies with packet:
---------------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int32_t | action | The action, should in this case be |
| | | 2 for scrape. |
| | | If 3 (for error) see errors_. |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Must match the sent transaction id. |
+-------------+---------------------+----------------------------------------+
The rest of the packet contains the following structures once for each info-hash
you asked in the scrape request.
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int32_t | complete | The total number of completed |
| | | downloads. |
+-------------+---------------------+----------------------------------------+
| int32_t | downloaded | The current number of connected seeds. |
+-------------+---------------------+----------------------------------------+
| int32_t | incomplete | The current number of connected |
| | | leechers. |
+-------------+---------------------+----------------------------------------+
errors
++++++
In case of a tracker error,
server replies packet:
----------------------
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int32_t | action | The action, in this case 3, for error. |
| | | See actions_. |
+-------------+---------------------+----------------------------------------+
| int32_t | transaction_id | Must match the transaction_id sent |
| | | from the client. |
+-------------+---------------------+----------------------------------------+
| int8_t[] | error_string | The rest of the packet is a string |
| | | describing the error. |
+-------------+---------------------+----------------------------------------+
actions
+++++++
The action fields has the following encoding:
* connect = 0
* announce = 1
* scrape = 2
* error = 3 (only in server replies)
extensions
++++++++++
The extensions field is a bitmask. The following
bits are assigned:
* 1 = authentication_.
authentication
--------------
The packet will have an authentication part
appended to it. It has the following format:
+-------------+---------------------+----------------------------------------+
| size | name | description |
+=============+=====================+========================================+
| int8_t | username_length | The number of characters in the |
| | | username. |
+-------------+---------------------+----------------------------------------+
| int8_t[] | username | The username, the number of characters |
| | | as specified in the previous field. |
+-------------+---------------------+----------------------------------------+
| uint8_t[8] | passwd_hash | sha1(packet + sha1(password)) |
| | | The packet in this case means the |
| | | entire packet except these 8 bytes |
| | | that are the password hash. These are |
| | | the 8 first bytes (most significant) |
| | | from the 20 bytes hash calculated. |
+-------------+---------------------+----------------------------------------+
credits
+++++++
Protocol designed by Olaf van der Spek
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