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https://github.com/bittorrent/bootstrap-dht

DHT bootstrap server
https://github.com/bittorrent/bootstrap-dht

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DHT bootstrap server

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README 

        
bootstrap-dht

=============



The DHT bootstrap server can be used as an introducer to the bittorrent

DHT network. Like the ones running at ``router.utorrent.com`` and

``router.bittorrent.com``.



BitTorrent clients can use this server to join the DHT, assuming some number

of clients are agreeing on using the same server.



The command line options are::



	usage: dht-bootstrap  [options]



	OPTIONS:

	--help                prints this message.

	--threads          spawns  threads (defaults to the

	                      number of hardware cores).

	--nodes            sets the number of nodes to keep in

	                      the node buffer. Once full, the oldest

	                      nodes are replaced as new nodes come in.

	--ping-queue       sets the max number of nodes to keep in

	                      the ping queue. Nodes are held in the queue

	                      for 15 minutes.

	--no-verify-id        disable filtering nodes based on their node ID

	                      and external IP (allow any node in on the

	                      node list to hand out).

	--ipv6            listen for IPv6 packets on the given address

	                      can be specified more than once

	--version    The client version to insert into all outgoing

	                      packets. The version format must be 2 characters

	                      followed by a dash and an integer.

	--dir           specify the directory where the node buckets are

	                      stored on disk. Defaults to ".".

	--port   Sets the port to listen on (for all interfaces)

	                      defaults to 6881

	--x-pollinate  

	                      if the ping queue becomes too small, request more

	                      nodes from this DHT node.



The first argument when launching the server is its own IP. This is not

only relevant for binding the socket to this interface but is also used when

generating its own DHT node ID.



The number of threads defaults to the number of CPU cores but can be

overridden by the ``--threads`` argument.



The number of DHT nodes to keep in the cache of nodes to hand out defaults

to 10000000 and can be overridden by ``--nodes``. It may not be lower than

1000.



The ping queue is the max number of nodes allowed in the queue waiting to

be pinged. Nodes are (ideally) pinged 15 minutes after seen. If too many

nodes are pinging the dht-bootstrapper to hold them all for 15 minutes

in the ping buffer, the rate of pinging is throttled to match.



For example, the default of 5000000 nodes in the ping buffer restricts the

ping rate to (5000000 / 900 = ) 5555 pings per second. Experience from

``router.utorrent.com`` suggests that about 45% of pings succeeds and end

up being added to the node buffer. At the default rate, that means the

entire node buffer is replaced every 66 minutes. i.e. once you're in the

node buffer, you'll be handed out to nodes for abut 66 minutes before you

are replaced by someone else.



The current rate at ``router.utorrent.com`` is about 20000 requests per second.

Every request returns 16 nodes. That means every node in the node buffer is

handed out once every (10000000 / 16 / 20000 ~=) 31 seconds.



Only nodes whose node ID match their external IP address (according to this_)

are pinged.



.. _this: http://libtorrent.org/dht_sec.html



``dht-bootstrap`` listens on port 6881 by default. You may specify a different

port using the ``--port`` command line option.



A more detailed description of how it's implemented can be found in the

header of ``main.cpp``.



The source for the bootstrap server is released under the MIT license.

Please contribute back fixes and improvements!



building

--------



To build, you need boost_ and boost-build installed. Build by running: ``b2``.



.. _boost: http://www.boost.org



If you prefer to build manually, just compile ``main.cpp``, ``bdecode.cpp`` and

link against the boost.system library as well as adding boost to your include

path.



To build you need a compiler with C++11 support.



acknowledgments

---------------



Thanks to following people who have contributed code or discovered

bugs in bootstrap-dht:



Team_LPJ@BoB working with Zero Day Initiative (ZDI)