#encoding: utf-8 
    import socket 
    from hashlib import sha1 
    from random import randint 
    from struct import unpack, pack 
    from socket import inet_aton, inet_ntoa 
    from bisect import bisect_left 
    from threading import Timer 
    from time import sleep 
    import MySQLdb 
    from datetime import * 
    import time 
    from bencode import bencode, bdecode 
    BOOTSTRAP_NODES = [ 
        ("router.bittorrent.com", 6881), 
        ("dht.transmissionbt.com", 6881), 
        ("router.utorrent.com", 6881) 
    ]  
    TID_LENGTH = 4 
    KRPC_TIMEOUT = 10 
    REBORN_TIME = 5 * 60 
    K = 8 
    def entropy(bytes): 
        s = "" 
        for i in range(bytes): 
            s += chr(randint(0, 255)) 
        return s 
    def random_id(): 
        hash = sha1() 
        hash.update( entropy(20) ) 
        return hash.digest() 
    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 = inet_ntoa(nodes[i+20:i+24]) 
            port = unpack("!H", nodes[i+24:i+26])[0] 
            n.append( (nid, ip, port) ) 
        return n 
    def encode_nodes(nodes): 
        strings = [] 
        for node in nodes: 
            s = "%s%s%s" % (node.nid, inet_aton(node.ip), pack("!H", node.port)) 
            strings.append(s) 
        return "".join(strings) 
    def intify(hstr): 
        return long(hstr.encode('hex'), 16)     
    def timer(t, f): 
        Timer(t, f).start() 
    class BucketFull(Exception): 
        pass 
    class KRPC(object): 
        def __init__(self): 
            self.types = { 
                "r": self.response_received, 
                "q": self.query_received 
            } 
            self.actions = { 
                "ping": self.ping_received, 
                "find_node": self.find_node_received, 
                "get_peers": self.get_peers_received, 
                "announce_peer": self.announce_peer_received, 
            } 
            self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
            self.socket.bind(("0.0.0.0", self.port)) 
        def response_received(self, msg, address): 
            self.find_node_handler(msg) 
        def query_received(self, msg, address): 
            try: 
                self.actions[msg["q"]](msg, address) 
            except KeyError: 
                pass 
        def send_krpc(self, msg, address): 
            try: 
                self.socket.sendto(bencode(msg), address) 
            except: 
                pass 
    class Client(KRPC): 
        def __init__(self, table): 
            self.table = table 
            timer(KRPC_TIMEOUT, self.timeout) 
            timer(REBORN_TIME, self.reborn) 
            KRPC.__init__(self) 
        def find_node(self, address, nid=None): 
            nid = self.get_neighbor(nid) if nid else self.table.nid 
            tid = entropy(TID_LENGTH) 
            msg = { 
                "t": tid, 
                "y": "q", 
                "q": "find_node", 
                "a": {"id": nid, "target": random_id()} 
            } 
            self.send_krpc(msg, address) 
        def find_node_handler(self, msg): 
            try: 
                nodes = decode_nodes(msg["r"]["nodes"]) 
                for node in nodes: 
                    (nid, ip, port) = node 
                    if len(nid) != 20: continue 
                    if nid == self.table.nid: continue 
                    self.find_node( (ip, port), nid ) 
            except KeyError: 
                pass 
        def joinDHT(self): 
            for address in BOOTSTRAP_NODES:  
                self.find_node(address) 
        def timeout(self): 
            if len( self.table.buckets ) < 2: 
                self.joinDHT() 
            timer(KRPC_TIMEOUT, self.timeout) 
        def reborn(self): 
            self.table.nid = random_id() 
            self.table.buckets = [ KBucket(0, 2**160) ] 
            timer(REBORN_TIME, self.reborn) 
        def start(self): 
            self.joinDHT() 
            while True: 
                try: 
                    (data, address) = self.socket.recvfrom(65536) 
                    msg = bdecode(data) 
                    self.types[msg["y"]](msg, address) 
                except Exception: 
                    pass 
        def get_neighbor(self, target): 
            return target[:10]+random_id()[10:] 
    class Server(Client): 
        def __init__(self, master, table, port): 
            self.table = table 
            self.master = master 
            self.port = port 
            Client.__init__(self, table) 
        def ping_received(self, msg, address): 
            try: 
                nid = msg["a"]["id"] 
                msg = { 
                    "t": msg["t"], 
                    "y": "r", 
                    "r": {"id": self.get_neighbor(nid)} 
                } 
                self.send_krpc(msg, address) 
                self.find_node(address, nid) 
            except KeyError: 
                pass 
        def find_node_received(self, msg, address): 
            try: 
                target = msg["a"]["target"] 
                neighbors = self.table.get_neighbors(target) 
                nid = msg["a"]["id"] 
                msg = { 
                    "t": msg["t"], 
                    "y": "r", 
                    "r": { 
                        "id": self.get_neighbor(target),  
                        "nodes": encode_nodes(neighbors) 
                    } 
                } 
                self.table.append(KNode(nid, *address)) 
                self.send_krpc(msg, address) 
                self.find_node(address, nid) 
            except KeyError: 
                pass 
        def get_peers_received(self, msg, address): 
            try: 
                infohash = msg["a"]["info_hash"] 
                neighbors = self.table.get_neighbors(infohash) 
                nid = msg["a"]["id"] 
                msg = { 
                    "t": msg["t"], 
                    "y": "r", 
                    "r": { 
                        "id": self.get_neighbor(infohash),  
                        "nodes": encode_nodes(neighbors) 
                    } 
                } 
                self.table.append(KNode(nid, *address)) 
                self.send_krpc(msg, address) 
                self.master.log(infohash) 
                self.find_node(address, nid) 
            except KeyError: 
                pass 
        def announce_peer_received(self, msg, address): 
            try: 
                infohash = msg["a"]["info_hash"] 
                nid = msg["a"]["id"] 
                msg = {  
                    "t": msg["t"], 
                    "y": "r", 
                    "r": {"id": self.get_neighbor(infohash)} 
                } 
                self.table.append(KNode(nid, *address)) 
                self.send_krpc(msg, address) 
                self.master.log(infohash) 
                self.find_node(address, nid) 
            except KeyError: 
                pass 
    class KTable(object): 
        def __init__(self, nid): 
            self.nid = nid 
            self.buckets = [ KBucket(0, 2**160) ] 
        def append(self, node): 
            index = self.bucket_index(node.nid) 
            try: 
                bucket = self.buckets[index] 
                bucket.append(node) 
            except IndexError: 
                return 
            except BucketFull: 
                if not bucket.in_range(self.nid): return 
                self.split_bucket(index) 
                self.append(node) 
        def get_neighbors(self, target): 
            nodes = [] 
            if len(self.buckets) == 0: return nodes 
            if len(target) != 20 : return nodes 
            index = self.bucket_index(target) 
            try: 
                nodes = self.buckets[index].nodes 
                min = index - 1 
                max = index + 1 
                while len(nodes) < K and ((min >= 0) or (max < len(self.buckets))): 
                    if min >= 0: 
                        nodes.extend(self.buckets[min].nodes) 
                    if max < len(self.buckets): 
                        nodes.extend(self.buckets[max].nodes) 
                    min -= 1 
                    max += 1 
                num = intify(target) 
                nodes.sort(lambda a, b, num=num: cmp(num^intify(a.nid), num^intify(b.nid))) 
                return nodes[:K] 
            except IndexError: 
                return nodes 
        def bucket_index(self, target): 
            return bisect_left(self.buckets, intify(target)) 
        def split_bucket(self, index): 
            old = self.buckets[index] 
            point = old.max - (old.max - old.min)/2 
            new = KBucket(point, old.max) 
            old.max = point 
            self.buckets.insert(index + 1, new) 
            for node in old.nodes[:]: 
                if new.in_range(node.nid): 
                    new.append(node) 
                    old.remove(node) 
        def __iter__(self): 
            for bucket in self.buckets: 
                yield bucket 
    class KBucket(object): 
        __slots__ = ("min", "max", "nodes") 
        def __init__(self, min, max): 
            self.min = min 
            self.max = max 
            self.nodes = [] 
        def append(self, node): 
            if node in self: 
                self.remove(node) 
                self.nodes.append(node) 
            else: 
                if len(self) < K: 
                    self.nodes.append(node) 
                else: 
                    raise BucketFull 
        def remove(self, node): 
            self.nodes.remove(node) 
        def in_range(self, target): 
            return self.min <= intify(target) < self.max 
        def __len__(self): 
            return len(self.nodes) 
        def __contains__(self, node): 
            return node in self.nodes 
        def __iter__(self): 
            for node in self.nodes: 
                yield node 
        def __lt__(self, target): 
            return self.max <= target 
    class KNode(object): 
        __slots__ = ("nid", "ip", "port") 
        def __init__(self, nid, ip, port): 
            self.nid = nid 
            self.ip = ip 
            self.port = port 
        def __eq__(self, other): 
            return self.nid == other.nid 
    #using example 
    class Master(object): 
        def __init__(self, f): 
            self.f = f 
            try: 
                self.conn=MySQLdb.connect(host='localhost',user='root',passwd='',db='bt',port=3306) 
                self.cur=self.conn.cursor() 
            except MySQLdb.Error,e: 
                print "Mysql Error %d: %s" % (e.args[0], e.args[1]) 
        def log(self, infohash): 
            try: