dht算法 python代码实现

以下是一个简单的基于Python的DHT算法实现：

import hashlib
import socket
import struct
import sys
import time

BOOTSTRAP_NODES = (
    ("router.bittorrent.com", 6881),
    ("dht.transmissionbt.com", 6881),
    ("router.utorrent.com", 6881)
)

TID_LENGTH = 4
RE_JOIN_INTERVAL = 30
TOKEN_LENGTH = 2
VALUES_LIMIT = 8

def entropy(length):
    return ''.join(chr(random.getrandbits(8)) for _ in range(length))

def get_neighbor(target, end=False):
    return target[:-1] + chr(ord(target[-1]) ^ end and 0xff or 0x01)

def decode_nodes(nodes):
    n = []
    length = len(nodes)
    if (length % 26) != 0:
        return n

    for i in range(0, length, 26):
        nid = nodes[i:i+20]
        ip = socket.inet_ntoa(nodes[i+20:i+24])
        port = struct.unpack("!H", nodes[i+24:i+26])[0]
        n.append((nid, ip, port))

    return n

class KNode:
    def __init__(self, nid, ip, port):
        self.nid = nid
        self.ip = ip
        self.port = port

class DHT:
    def __init__(self, bind_ip, bind_port, max_node_qsize):
        self.bind_ip = bind_ip
        self.bind_port = bind_port
        self.max_node_qsize = max_node_qsize

        self.is_running = False
        self.nodes = {}
        self.routing_table = {}

    def start(self):
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
        try:
            self.socket.bind((self.bind_ip, self.bind_port))
        except:
            print('Bind Error!')
            sys.exit()
        print('Listening on %s:%d' % (self.bind_ip, self.bind_port))

        self.is_running = True
        while self.is_running:
            try:
                self.tick()
                data, (ip, port) = self.socket.recvfrom(4096)
                if data:
                    self.on_message((data, (ip, port)))
            except:
                pass

    def stop(self):
        self.is_running = False
        if self.socket:
            self.socket.close()

    def tick(self):
        t = int(time.time())
        for node in self.nodes.values():
            if node.get('last_seen', 0) + RE_JOIN_INTERVAL < t:
                self.remove_node(node['id'])

    def on_message(self, msg):
        msg_type = ord(msg[0][0])
        if msg_type == 0x08:
            self.on_find_node(msg)
        elif msg_type == 0x0a:
            self.on_get_peers(msg)
        elif msg_type == 0x0f:
            self.on_announce_peer(msg)

    def on_find_node(self, msg):
        tid = msg[0:4]
        target_id = msg[4:24]
        node_id = msg[24:]

        nodes = self.get_nodes(target_id)
        token = entropy(TOKEN_LENGTH)

        if nodes:
            for node in nodes:
                msg = struct.pack("!20s", node.nid) + socket.inet_aton(node.ip) + struct.pack("!H", node.port)
                self.socket.sendto(b"\x00\x00\x00\x00" + tid + msg, (node.ip, node.port))
        else:
            self.socket.sendto(b"\x00\x00\x00\x00" + tid + b"d1:rd2:id20:" + self.get_neighbor(target_id).encode() + b"e1:t2:aa1:y1:re", (node.ip, node.port))

    def on_get_peers(self, msg):
        tid = msg[0:4]
        infohash = msg[4:24]
        node_id = msg[24:]

        token = entropy(TOKEN_LENGTH)
        values = []

        if infohash == node_id:
            values.append((self.bind_ip, self.bind_port))
        else:
            # Fetch values from the DHT storage
            pass

        if values:
            token = entropy(TOKEN_LENGTH)
            for v in values[:VALUES_LIMIT]:
                self.socket.sendto(b"\x00\x00\x00\x00" + tid + b"d1:rd2:id20:" + self.get_neighbor(infohash).encode() + b"5:token" + str(len(token)).encode() + b":" + token.encode() + b"5:value" + str(len(v)).encode() + b":" + v.encode() + b"ee", (node.ip, node.port))
        else:
            nodes = self.get_nodes(infohash)
            if nodes:
                for node in nodes:
                    msg = struct.pack("!20s", node.nid) + socket.inet_aton(node.ip) + struct.pack("!H", node.port)
                    self.socket.sendto(b"\x00\x00\x00\x00" + tid + b"d1:rd2:id20:" + self.get_neighbor(infohash).encode() + b"e1:t2:aa1:y1:re", (node.ip, node.port))
            else:
                self.socket.sendto(b"\x00\x00\x00\x00" + tid + b"d1:rd2:id20:" + self.get_neighbor(infohash).encode() + b"e1:t2:aa1:y1:re", (node.ip, node.port))

    def on_announce_peer(self, msg):
        pass

    def get_nodes(self, target):
        nodes = []
        for nid in self.routing_table.get(target, []):
            if nid in self.nodes:
                nodes.append(KNode(nid, self.nodes[nid]['ip'], self.nodes[nid]['port']))
        return nodes

    def add_node(self, node_id, ip, port):
        if node_id not in self.nodes and len(self.nodes) < self.max_node_qsize:
            self.nodes[node_id] = {'ip': ip, 'port': port, 'last_seen': time.time()}
            self.routing_table.setdefault(node_id[0], set())
            self.routing_table[node_id[0]].add(node_id)

    def remove_node(self, node_id):
        if node_id in self.nodes:
            del self.nodes[node_id]
            self.routing_table[node_id[0]].remove(node_id)

    def get_neighbor(self, target):
        return get_neighbor(target, True)

    def join_DHT(self):
        for addr in BOOTSTRAP_NODES:
            node_id = hashlib.sha1(entropy(20).encode()).digest()
            self.add_node(node_id, self.bind_ip, self.bind_port)
            self.socket.sendto(b"\x00\x00\x00\x00" + entropy(TID_LENGTH).encode() + b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" + node_id, addr)

    def bootstrap(self):
        while len(self.nodes) < self.max_node_qsize:
            self.join_DHT()
            time.sleep(1)

如果您想要更深入地了解DHT算法的实现，建议您参考更为详细的教程和资料。