basic client implementation

index.js

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+exports.Client = Client
+// TODO: exports.Server = Server
+// TODO: support connecting to UDP trackers (http://www.bittorrent.org/beps/bep_0015.html)
+
+var bncode = require('bncode')
+var compact2string = require('compact2string')
+var EventEmitter = require('events').EventEmitter
+var extend = require('extend.js')
+var http = require('http')
+var inherits = require('inherits')
+var querystring = require('querystring')
+
+inherits(Client, EventEmitter)
+
+function Client (peerId, port, torrent, opts) {
+  var self = this
+  if (!(self instanceof Client)) return new Client(peerId, port, torrent)
+  EventEmitter.call(self)
+  self._opts = opts || {}
+
+  // required
+  self._peerId = peerId
+  self._port = port
+  self._infoHash = torrent.infoHash
+  self._torrentLength = torrent.length
+  self._announce = torrent.announce
+
+  // optional
+  self._numWant = self._opts.numWant || 80
+  self._intervalMs = self._opts.interval || (30 * 60 * 1000) // default: 30 minutes
+
+  self._interval = null
+}
+
+Client.prototype.start = function (opts) {
+  var self = this
+  opts = opts || {}
+  opts.event = 'started'
+  self._request(opts)
+
+  self.setInterval(self._intervalMs) // start announcing on intervals
+}
+
+Client.prototype.stop = function (opts) {
+  var self = this
+  opts = opts || {}
+  opts.event = 'stopped'
+  self._request(opts)
+
+  self.setInterval(0) // stop announcing on intervals
+}
+
+Client.prototype.complete = function (opts) {
+  var self = this
+  opts = opts || {}
+  opts.event = 'completed'
+  self._request(opts)
+}
+
+Client.prototype.update = function (opts) {
+  var self = this
+  opts = opts || {}
+  self._request(opts)
+}
+
+Client.prototype.setInterval = function (intervalMs) {
+  var self = this
+  if (self._interval) {
+    clearInterval(self._interval)
+  }
+
+  self._intervalMs = intervalMs
+  if (self._intervalMs) {
+    self._interval = setInterval(self.update.bind(self), self._intervalMs)
+  }
+}
+
+/**
+ * Send a request to the tracker
+ */
+Client.prototype._request = function (opts) {
+  var self = this
+  opts = extend({
+    info_hash: bytewiseEncodeURIComponent(self._infoHash),
+    peer_id: bytewiseEncodeURIComponent(self._peerId),
+    port: self._port,
+    left: self._torrentLength - (opts.downloaded || 0),
+    compact: 1,
+    numwant: self._numWant,
+    uploaded: 0, // default, user should provide real value
+    downloaded: 0 // default, user should provide real value
+  }, opts)
+
+  if (self._trackerId) {
+    opts.trackerid = self._trackerId
+  }
+
+  var q = querystring.stringify(opts)
+
+  self._announce.forEach(function (announce) {
+    var url = announce + '?' + q
+    var req = http.get(url, function (res) {
+      var data = ''
+      if (res.statusCode !== 200) {
+        res.resume() // consume the whole stream
+        self.emit('error', new Error('Invalid response code ' + res.statusCode + ' from tracker'))
+        return
+      }
+      res.on('data', function (chunk) {
+        data += chunk
+      })
+      res.on('end', function () {
+        self._handleResponse(data, announce)
+      })
+    })
+
+    req.on('error', function (err) {
+      self.emit('error', req)
+    })
+  })
+}
+
+Client.prototype._handleResponse = function (data, announce) {
+  var self = this
+
+  try {
+    data = bncode.decode(data)
+  } catch (err) {
+    return self.emit('error', new Error('Error decoding tracker response: ' + err.message))
+  }
+  var failure = data['failure reason']
+  if (failure) {
+    return self.emit('error', new Error(failure))
+  }
+
+  var warning = data['warning message']
+  if (warning) {
+    console.warn(warning)
+  }
+
+  var interval = data.interval || data['min interval']
+  if (interval && !self._opts.interval && self._intervalMs !== 0) {
+    // use the interval the tracker recommends, UNLESS the user manually specifies an
+    // interval they want to use
+    self.setInterval(interval)
+  }
+
+  var trackerId = data['tracker id']
+  if (trackerId) {
+    // If absent, do not discard previous trackerId value
+    self._trackerId = trackerId
+  }
+
+  self.emit('update', {
+    announce: announce,
+    complete: data.complete,
+    incomplete: data.incomplete
+  })
+
+  if (Buffer.isBuffer(data.peers)) {
+    // tracker returned compact response
+    var addrs = compact2string.multi(data.peers)
+    addrs.forEach(function (addr) {
+      self.emit('peer', addr)
+    })
+  } else if (Array.isArray(data.peers)) {
+    // tracker returned normal response
+    data.peers.forEach(function (peer) {
+      var ip = peer.ip
+      self.emit('peer', ip[0] + '.' + ip[1] + '.' + ip[2] + '.' + ip[3] + ':' + peer.port)
+    })
+  }
+}
+
+function bytewiseEncodeURIComponent (buf) {
+  if (!Buffer.isBuffer(buf)) {
+    buf = new Buffer(buf, 'hex')
+  }
+  return escape(buf.toString('binary'))
+}

package.json

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+{
+  "name": "bittorrent-tracker",
+  "description": "Simple, robust, BitTorrent tracker (client & server) implementation",
+  "version": "0.0.1",
+  "author": {
+    "name": "Feross Aboukhadijeh",
+    "email": "feross@feross.org",
+    "url": "http://feross.org/"
+  },
+  "bugs": {
+    "url": "https://github.com/feross/bittorrent-tracker/issues"
+  },
+  "dependencies": {
+    "bncode": "^0.5.2",
+    "compact2string": "^1.2.0",
+    "extend.js": "0.0.1",
+    "inherits": "^2.0.1",
+    "querystring": "^0.2.0"
+  },
+  "devDependencies": {
+    "parse-torrent": "^0.6.0",
+    "tape": "2.x"
+  },
+  "homepage": "http://webtorrent.io",
+  "keywords": [
+    "torrent",
+    "bittorrent",
+    "tracker",
+    "stream",
+    "peer",
+    "wire",
+    "p2p",
+    "peer-to-peer"
+  ],
+  "license": "MIT",
+  "main": "index.js",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/feross/bittorrent-tracker.git"
+  },
+  "scripts": {
+    "test": "tape test/*.js"
+  }
+}