exbt

This script is still in beta.

Naive implementation of BitTorrent Client (in Elixir), quick and dirty.

Usage

Initializing a job

Run iex exbt.exs to load the module into interactive shell

Create a new download job by providing:

The .torrent file
An non-exist dir for storing job's data

iex> myjob = Job.create("/tmp/test_job", "test/centos.torrent")
...
...
iex> Job.start(myjob)

Or from existing job dir:

iex> myjob = Job.load("/tmp/test_job")
...
...
iex> Job.start(myjob)

Avaiable Commands

Create a new job

myjob = Job.create(<job_dir>, <path_of_torrent_file>)

Load existing job

myjob = Job.load(<job_dir>)

Closing an existing job

This will stop all process that relates to this job

Job.close(myjob)

Start the job

Start connecting to peers and start downloading

Job.start(myjob)

Stop the job

Disconnect from peers. Stop all actions.

Job.stop(myjob)

Pause download/uploac

Stop download/uploading data, but keep current connections

Job.pause(myjob)

Resume download/upload

Start download/uploading data

Job.resume(myjob)

Getting progress of download

iex(5)> Job.progress(job)
%{finished: 1105, percentage: 100.0, unfinished: 0}

iex(6)> Job.finished?(myjob)
true

Set the max-allowed connections

Job.set_max_connections(myjob, 5)

Display file info listed in the torrent metadata

iex(8)> Job.files(myjob)
[
  %{
    "length" => 578813952,
    "offset_start" => 0,
    "path" => "CentOS-7-x86_64-NetInstall-1908/CentOS-7-x86_64-NetInstall-1908.iso",
    "piece_index_range" => 0..1104
  },
  %{
    "length" => 598,
    "offset_start" => 578813952,
    "path" => "CentOS-7-x86_64-NetInstall-1908/sha256sum.txt",
    "piece_index_range" => 1104..1104
  },
  %{
    "length" => 1458,
    "offset_start" => 578814550,
    "path" => "CentOS-7-x86_64-NetInstall-1908/sha256sum.txt.asc",
    "piece_index_range" => 1104..1104
  }
]

Display overall status

iex(9)> Job.status(myjob)
%{
  connections: 0,
  files: [
    %{
      "length" => 578813952,
      "offset_start" => 0,
      "path" => "CentOS-7-x86_64-NetInstall-1908/CentOS-7-x86_64-NetInstall-1908.iso",
      "piece_index_range" => 0..1104
    },
    %{
      "length" => 598,
      "offset_start" => 578813952,
      "path" => "CentOS-7-x86_64-NetInstall-1908/sha256sum.txt",
      "piece_index_range" => 1104..1104
    },
    %{
      "length" => 1458,
      "offset_start" => 578814550,
      "path" => "CentOS-7-x86_64-NetInstall-1908/sha256sum.txt.asc",
      "piece_index_range" => 1104..1104
    }
  ],
  job_dir: "/tmp/test_bt",
  progress: %{finished: 1105, percentage: 100.0, unfinished: 0}
}

Get the job's dir

iex(10)> Job.dir(myjob)
"/tmp/test_bt"

References

https://www.bittorrent.org/beps/bep_0003.html

Official spec of Bittorrent DHT Protocol (Mainline DHT)

http://www.bittorrent.org/beps/bep_0009.html

https://www.libtorrent.org/dht_store.html

Documents

FileServer

FileServer.Functions

init_from_new_torrent
init_from_torrent_info_hash
init_from_new_metadata
init_from_existing_job

DHTBucket

DHTBucket.Struct

capacity
nodes
candidates
last_changed

Bucket <id> contains node with distance falls between [2^<id-1>, 2^<id> - 1]

For example a DHT table with 4-bit node-space should have buckets:

bucket0: 0000 ~ 0000 (current node)
bucket1: 0001 ~ 0001
bucket2: 0010 ~ 0011
bucket3: 0100 ~ 0111

DHTBucket.Functions

new_bucket
add_node
add_candidate
delete_node
get_node_by_id
get_nodes
get_n_nodes
has_node?
has_candidate?
without_node(node_id)
get_most_trusty_node
get_trusty_nodes
get_most_questionable_node
get_questionable_nodes
size
size_info
is_full?
is_fresh?
refresh_node
insert_to_sorted_nodes
healthcheck_threshold

DHTTable

DHTTable.Attributes

buckets
reference_node_id

DHTTable.Functions

new_table
get_node
get_nodes
reference_node_id
set_bucket
get_k_nearest_nodes
get_bucket_num_by_distance(distance)
get_corresponding_bucket
get_corresponding_bucket_num
size

KRPC_Msg

KRPC_Msg.Functions

General functions:

get_error_types
get_sender_id
error_code
to_bin
from_bin
from_buffer
gen_transaction_id
get_query_type

Functions that build KRPC messages:

ping
ping_response
find_node
find_node_response
get_peers
get_peers_response
announce_peer
announce_peer_response
response
error

DHTServer

@ping_response_threshold
@ping_response_threshold_sec
@krpc_query_timeout
@api_general_timeout
@api_search_nodes_timeout

DHTServer.Struct (as GenServer state)

node_id: node_id
table: DHTTable
peer_info: %{info_hash => compact_peer_list}
token_server: token server pid
waiting_response: %{transaction_id => {req_msg, req_pid} }
socket: udp socket

DHTServer.Functions

start_link
init
ping
find_node
node_id
search_peers
search_nodes
schedule_node_check
send_krpc_msg!
do_add_node
do_on_krpc_msg

DHTServer.handle_call

:node_id
:ping
:add_node
:find_node
:get_peers
:stored_nearest_nodes
:send_krpc_msg

DHTServer.handle_cast

:bootstrap

DHTServer.handle_info

:udp
:krpc
:check_node_aliveness
:krpc_query_timeout

TokenServer

TokenServer.State:

secret
old_secret

TokenServer.Functions

start_link
init
is_valid_token?
request_token
random_secret
calculate_token

TokenServer.handle_call

:is_valid_token/2
:request_token/1

TokenServer.handle_info

:loop_renew_secret

DHTNode

DHTNode.Struct:

id
ip
port
last_active

DHTNode.Functions

compact_info
contact_info

DHTUtils

DHTUtils.Functions

count_0_prefix_length
node_distance_binary
gen_random_bitstring
gen_random_string
gen_node_id
parse_peers_val
parse_nodes_val
get_magnet_info_hash

Rakasha/exbt