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BitTorrent Framework

BitTorrent Framework. Background. BT is a very popular peer to peer protocol with many implementations: http://en.wikipedia.org/wiki/Comparison_of_BitTorrent_clients The first one was created in Python by Bram Cohen. Workshop goal. Exploit BitTorrent protocol to give less for more.

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BitTorrent Framework

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  1. BitTorrent Framework

  2. Background • BT is a very popular peer to peer protocol with many implementations: • http://en.wikipedia.org/wiki/Comparison_of_BitTorrent_clients • The first one was created in Python by Bram Cohen.

  3. Workshop goal • Exploit BitTorrent protocol to give less for more. • Real world motivation • Places with low upload (Africa, China) • Bad character

  4. How do I test my idea • Create my own (or modified) BitTorrent client. • Run together: • “The World”: N “standard” BitTorrent Clients. • Specific upload rate • Various download stages • My Client • See how much time my client ran, and what was its upload / download ratio.

  5. Tracker BT BT BT BT BT BT BT BT BT BT BT Execution example run-all.sh

  6. How does it work? • Run tracker • Run the “world” • Run your client (if given)

  7. How does it work? • Both tracker and the “world” run on the same computer • we have • pc-hanoch-w1 • pc-hanoch-w2 • Please reserve time in: • http://0368350023.wikispaces.com/ • Or from course www - "Scheduling computers for tests."

  8. The main script - run_all.sh • Location: • /users/courses/hanochworkshop/bittorrent • Run_all.sh: • Parameters: • Start / stop • My client – optional

  9. run_all.sh operation • Start: • Create download directory • Run the “world” • Each world client starts with different “saved” amount. • Run “my client” – if given • All uploads rates are restricted. • Stop • Kill all python threads

  10. To run client separately: • BitTornado-My-Client/btdownloadheadless.py • --saveas /vol/scratch/bt-download/picture.tst.bmp • --max_upload_rate 70 • --security 0 • ./picture.pc-hanoch-w[1,2].bmp.torrent • Not necessarily on the same machine as the world.

  11. What implementation we use • The clients are a modified version based on an up to date version of Bram Python Client. • Modifications: • “World” clients • do not print as it would only make a mess • reincarnate after the finish to make a real world feel. • “My Client” template – kills all clients when finished • All clients – print total time

  12. Python • Very common script language • Intuitive and readable • References: • python.org :http://docs.python.org/reference/ • http://wiki.python.org/moin/BeginnersGuide/NonProgrammers • http://wiki.python.org/moin/BeginnersGuide/Programmers • The book "Think like a Computer Scientist in Python" has a very good reputation:

  13. My Client • We supply a default “My Client” which is like the “standard” one. • If you want you may replace it with any other implementation, with certain reservations: • Remember we compare to our client. • It does not count to download a faster client than our client and simply say it is faster. • Client should either limit it’s upload rate, or be able to work with trickle.

  14. Getting started • Run the environment • ssh pc-hanoch-w[1,2] • cd /users/courses/hanochworkshop/bittorrent • run_all.sh • start • [BitTornado-My-Client/btdownloadheadless.py] • Note tracker prints a message for each GET. • You can connect to the tracker with a browser at: • http://pc-hanoch-w1:6970/ • Do ls -l /vol/scratch/bt-download/ to see downloaded files

  15. What is it doing? • Run bttrack. • Copy From FreshFiles a set of “downloaded” files to download directory. • Run X seeds • Run a python client per “downloaded” file. • Run my client if given

  16. For debug: run client separately • ./run_all.sh start to start the world • BitTornado-My-Client/btdownloadheadless.py • --saveas /vol/scratch/bt-download/picture.tst.bmp • --max_upload_rate 70 • --security 0 • ./picture.pc-hanoch-w[1,2].bmp.torrent • Start debug. • Use your favorite debug environment. • IDLE is standard source level debugger.

  17. Directory Structure • BitTornado-My-Client – • high level application • BitTornado-My-Client/BitTornado – • services • BitTornado-My-Client/BitTornado/BT1 – • Actual work

  18. Client Operation • btdownloadheadless.py – First to run. • Performs initializations. • get_response – parse the .torrent • Infohash – the ID of the .torrent • startEngine – Start connection with peers • startRerequester - Start connection with tracker • Run rawserver.listen_forever from RawServer.py. • listen_forever is: • Polling port • executing func() from a task queue.

  19. Receiving messages • From listen_forever loop it goes to: • BT1/Connecter.py/got_message • CHOKE • UNCHOKE • INTERESTED • NOT_INTERESTED • BITFIELD • REQUEST • CANCEL • PIECE • HAVE

  20. Influencing decisions • Can be done in in one of the callbacks which spring from Connecter.py / got_message: • Downloader.py • HAVE->got_have->send_interested • maybe check connection before sending?

  21. BT tracker • Send GET request in Rerequester.py / announce • Receive GET data in thread in Rerequester.py / _rerequest

  22. Influencing decisions • In Encrypter.py / start_connection or _start_connection_from_queue For instance try different max_connections. _rerequest_single – check timout for scheduling.

  23. Policy • Choker.py/_round_robin – decide who to choke / optimistically un choke / send_have to. • Downloader.py / _request_more. • PiecePicker.py / next - rarest piece, etc. • got_unchoke->_request_more->next…

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