app.js

var utils = require("./utils");
var bencode = require('node-bencode');
var dns = require('dns');
var args = process.argv.slice(2);

var meid = utils.genId();
var ip_reborn;
var ip;
var port;
var tick;
var sock;
var port = parseInt(process.argv[2]);

var MAX_UDP_PER_SECOND = 250; // adjust this value to control upstream speed

var nodes = [];
var nCount = 0;

function init() {
    var dgram = require("dgram");
    sock = dgram.createSocket("udp4");
    sock.on("message", onRecv);
    sock.on("listening", onSockCreated);
    sock.bind(port);
}

function onSockCreated() {
    var address = sock.address();
    ip = address.address;
    port = address.port;
    dns.resolve4('router.bittorrent.com', function(err, addresses) {
    	if(err == null) {
            ip_reborn = addresses[0];
            find_node(addresses[0], 6881);
            tick = setTimeout(function() {
                    find_node(addresses[0], 6881);
            }, 5 * 1000);
        } else {
            console.log('DHT init node domain resolve failed');
        }
    });
    setInterval(function() {
        send();
    }, 1000);
}

function find_node(ip, port) {
    var tid = utils.genTid();
    var msg = {
        "t": tid,
        "y": "q",
        "q": "find_node",
        "a": {"id": utils.getNeighbor(meid), "target": utils.genId()}
    };
    var encoded = bencode.encode(msg);
    try {
        //console.log('send first package');
        sock.send(encoded, 0, encoded.length, port, ip);
    } catch(e) { }
}

function onRecv(msg, rinfo) {
    var data = bencode.decode(msg);
    //console.log(data);
    if(data == null || data.y == null) {
        return;
    }
    // TODO: 收到find_node回复
    if(data.y.toString() === 'r' && nCount < MAX_UDP_PER_SECOND) {
        if(tick != null) {
            clearTimeout(tick);
            tick = null;
        }
        var buf = data.r.nodes;
        if(buf == null) {
            return;
        }
        // 返回nodes的节点为活跃节点，加入数组中
        var targetid = utils.genId();
        var count = buf.length / 26;
        var offset = 0;
        for(var i = 0; i < count; i++) {
            offset += 20;
            var nip = utils.buf2ip(buf.slice(offset, offset + 4));
            offset += 4;
            var nport = utils.buf2port(buf.slice(offset, offset + 2));
            if(nport > 65535 || nport < 0) {
                continue;
            }
            offset += 2;
            nodes.push({ip: nip, port: nport});
            nCount++;
            if(nCount >= MAX_UDP_PER_SECOND) {
                break;
            }
        }
    } else if(data.y.toString() === 'q' && data.q.toString() === 'get_peers') {
    	// infohash
		console.log(utils.id2str(data.a.info_hash));
    }
}

function send() {
    //console.log("sent " + nodes.length + " packets");
    if(nCount < 2) {
        find_node(ip_reborn, 6881);
    }
    for(var i = 0; nodes[i]; i++) {
        var node = nodes[i];
        find_node(node.ip, node.port);
    }
    nodes = [];
    nCount = 0;
}

init();