tracker.py

# pytorrent-tracker.py
# A bittorrent tracker

from http.server import BaseHTTPRequestHandler, HTTPServer
from threading import Thread
from logging import basicConfig, info, INFO
from pickle import dump, load
from socket import inet_aton
from struct import pack
from urllib.request import urlopen
from urllib.parse import parse_qs

from bencode import encode
from simpledb import Database

def decode_request(path):
	""" Return the decoded request string. """

	# Strip off the start characters
	if path[:1] == "?":
		path = path[1:]
	elif path[:2] == "/?":
		path = path[2:]

	return parse_qs(path)

def add_peer(torrents, info_hash, peer_id, ip, port):
	""" Add the peer to the torrent database. """

	# If we've heard of this, just add the peer
	if info_hash in torrents:
		# Only add the peer if they're not already in the database
		if (peer_id, ip, port) not in torrents[info_hash]:
			torrents[info_hash].append((peer_id, ip, port))
	# Otherwise, add the info_hash and the peer
	else:
		torrents[info_hash] = [(peer_id, ip, port)]

def make_compact_peer_list(peer_list):
	""" Return a compact peer string, given a list of peer details. """

	peer_string = ""
	for peer in peer_list:
		ip = inet_aton(peer[1])
		port = pack(">H", int(peer[2]))

		peer_string += (ip + port)

	return peer_string

def make_peer_list(peer_list):
	""" Return an expanded peer list suitable for the client, given
	the peer list. """

	peers = []
	for peer in peer_list:
		p = {}
		p["peer id"] = peer[0]
		p["ip"] = peer[1]
		p["port"] = int(peer[2])

		peers.append(p)

	return peers

def peer_list(peer_list, compact):
	""" Depending on compact, dispatches to compact or expanded peer
	list functions. """

	if compact:
		return make_compact_peer_list(peer_list)
	else:
		return make_peer_list(peer_list)

class RequestHandler(BaseHTTPRequestHandler):
	def do_GET(s):
		""" Take a request, do some some database work, return a peer
		list response. """

		# Decode the request
		package = decode_request(s.path)

		if not package:
			s.send_error(403)
			return

		# Get the necessary info out of the request
		info_hash = package["info_hash"][0]
		compact = bool(package["compact"][0])
		ip = s.client_address[0]
		port = package["port"][0]
		peer_id = package["peer_id"][0]

		add_peer(s.server.torrents, info_hash, peer_id, ip, port)

		# Generate a response
		response = {}
		response["interval"] = s.server.interval
		response["complete"] = 0
		response["incomplete"] = 0
		response["peers"] = peer_list( \
		s.server.torrents[info_hash], compact)

		# Send off the response
		s.send_response(200)
		s.end_headers()
		s.wfile.write(encode(response))

		# Log the request, and what we send back
		info("PACKAGE: %s", package)
		info("RESPONSE: %s", response)

	def log_message(self, format, *args):
		""" Just supress logging. """

		return

class Tracker():
	def __init__(self, host = "", port = 9010, interval = 5, \
		torrent_db = "tracker.db", log = "tracker.log", \
		inmemory = True):
		""" Read in the initial values, load the database. """

		self.host = host
		self.port = port

		self.inmemory = inmemory

		self.server_class = HTTPServer
		self.httpd = self.server_class((self.host, self.port), \
			RequestHandler)

		self.running = False	# We're not running to begin with

		self.server_class.interval = interval

		# Set logging info
		basicConfig(filename = log, level = INFO)

		# If not in memory, give the database a file, otherwise it
		# will stay in memory
		if not self.inmemory:
			self.server_class.torrents = Database(torrent_db)
		else:
			self.server_class.torrents = Database(None)

	def runner(self):
		""" Keep handling requests, until told to stop. """

		while self.running:
			self.httpd.handle_request()

	def run(self):
		""" Start the runner, in a seperate thread. """

		if not self.running:
			self.running = True

			self.thread = Thread(target = self.runner)
			self.thread.start()

	def send_dummy_request(self):
		""" Send a dummy request to the server. """

		# To finish off httpd.handle_request()
		address = "http://127.0.0.1:" + str(self.port)
		urlopen(address)

	def stop(self):
		""" Stop the thread, and join to it. """

		if self.running:
			self.running = False

			self.send_dummy_request()
			self.thread.join()

	def __del__(self):
		""" Stop the tracker thread, write the database. """

		self.stop()
		self.httpd.server_close()