bittorrent-tracker/lib/client/websocket-tracker.js

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module.exports = WebSocketTracker
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var debug = require('debug')('bittorrent-tracker:websocket-tracker')
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var extend = require('xtend')
var hat = require('hat')
var inherits = require('inherits')
var Peer = require('simple-peer')
var Socket = require('simple-websocket')
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var common = require('../common')
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var Tracker = require('./tracker')
// Use a socket pool, so tracker clients share WebSocket objects for the same server.
// In practice, WebSockets are pretty slow to establish, so this gives a nice performance
// boost, and saves browser resources.
var socketPool = {}
var RECONNECT_VARIANCE = 30 * 1000
var RECONNECT_MINIMUM = 5 * 1000
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var OFFER_TIMEOUT = 50 * 1000
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inherits(WebSocketTracker, Tracker)
function WebSocketTracker (client, announceUrl, opts) {
var self = this
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Tracker.call(self, client, announceUrl)
debug('new websocket tracker %s', announceUrl)
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self.peers = {} // peers (offer id -> peer)
self.socket = null
self.reconnecting = false
self._openSocket()
}
WebSocketTracker.prototype.DEFAULT_ANNOUNCE_INTERVAL = 30 * 1000 // 30 seconds
WebSocketTracker.prototype.announce = function (opts) {
var self = this
if (self.destroyed || self.reconnecting) return
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if (!self.socket.connected) {
return self.socket.once('connect', self.announce.bind(self, opts))
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}
// Limit the number of offers that are generated, since it can be slow
var numwant = Math.min(opts.numwant, 10)
self._generateOffers(numwant, function (offers) {
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var params = extend(opts, {
numwant: numwant,
info_hash: self.client._infoHashBinary,
peer_id: self.client._peerIdBinary,
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offers: offers
})
if (self._trackerId) params.trackerid = self._trackerId
self._send(params)
})
}
WebSocketTracker.prototype.scrape = function (opts) {
var self = this
if (self.destroyed || self.reconnecting) return
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self._onSocketError(new Error('scrape not supported ' + self.announceUrl))
}
WebSocketTracker.prototype.destroy = function (onclose) {
var self = this
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if (self.destroyed) return onclose && onclose()
self.destroyed = true
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clearInterval(self.interval)
delete socketPool[self.announceUrl]
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self.socket.removeListener('connect', self._onSocketConnectBound)
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self.socket.removeListener('data', self._onSocketDataBound)
self.socket.removeListener('close', self._onSocketCloseBound)
self.socket.removeListener('error', self._onSocketErrorBound)
self._onSocketConnectBound = null
self._onSocketErrorBound = null
self._onSocketDataBound = null
self._onSocketCloseBound = null
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self.socket.on('error', noop) // ignore all future errors
try {
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self.socket.destroy(onclose)
} catch (err) {
if (onclose) onclose()
}
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self.socket = null
}
WebSocketTracker.prototype._openSocket = function () {
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var self = this
self.destroyed = false
self._onSocketConnectBound = self._onSocketConnect.bind(self)
self._onSocketErrorBound = self._onSocketError.bind(self)
self._onSocketDataBound = self._onSocketData.bind(self)
self._onSocketCloseBound = self._onSocketClose.bind(self)
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self.socket = socketPool[self.announceUrl]
if (!self.socket) {
self.socket = socketPool[self.announceUrl] = new Socket(self.announceUrl)
self.socket.on('connect', self._onSocketConnectBound)
}
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self.socket.on('data', self._onSocketDataBound)
self.socket.on('close', self._onSocketCloseBound)
self.socket.on('error', self._onSocketErrorBound)
}
WebSocketTracker.prototype._onSocketConnect = function () {
var self = this
if (self.destroyed) return
if (self.reconnecting) {
self.reconnecting = false
self.announce(self.client._defaultAnnounceOpts())
}
}
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WebSocketTracker.prototype._onSocketData = function (data) {
var self = this
if (self.destroyed) return
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try {
data = JSON.parse(data)
} catch (err) {
self.client.emit('warning', new Error('Invalid tracker response'))
return
}
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if (data.info_hash !== self.client._infoHashBinary) {
debug(
'ignoring websocket data from %s for %s (looking for %s: reused socket)',
self.announceUrl, common.binaryToHex(data.info_hash), self.client.infoHash
)
return
}
if (data.peer_id && data.peer_id === self.client._peerIdBinary) {
// ignore offers/answers from this client
return
}
debug(
'received %s from %s for %s',
JSON.stringify(data), self.announceUrl, self.client.infoHash
)
var failure = data['failure reason']
if (failure) return self.client.emit('warning', new Error(failure))
var warning = data['warning message']
if (warning) self.client.emit('warning', new Error(warning))
var interval = data.interval || data['min interval']
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if (interval) self.setInterval(interval * 1000)
var trackerId = data['tracker id']
if (trackerId) {
// If absent, do not discard previous trackerId value
self._trackerId = trackerId
}
if (data.complete != null) {
self.client.emit('update', {
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announce: self.announceUrl,
complete: data.complete,
incomplete: data.incomplete
})
}
var peer
if (data.offer && data.peer_id) {
debug('creating peer (from remote offer)')
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peer = new Peer({
trickle: false,
config: self.client._rtcConfig,
wrtc: self.client._wrtc
})
peer.id = common.binaryToHex(data.peer_id)
peer.once('signal', function (answer) {
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var params = {
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info_hash: self.client._infoHashBinary,
peer_id: self.client._peerIdBinary,
to_peer_id: data.peer_id,
answer: answer,
offer_id: data.offer_id
}
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if (self._trackerId) params.trackerid = self._trackerId
self._send(params)
})
peer.signal(data.offer)
self.client.emit('peer', peer)
}
if (data.answer && data.peer_id) {
var offerId = common.binaryToHex(data.offer_id)
peer = self.peers[offerId]
if (peer) {
peer.id = common.binaryToHex(data.peer_id)
peer.signal(data.answer)
self.client.emit('peer', peer)
clearTimeout(peer.trackerTimeout)
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peer.trackerTimeout = null
delete self.peers[offerId]
} else {
debug('got unexpected answer: ' + JSON.stringify(data.answer))
}
}
}
WebSocketTracker.prototype._onSocketClose = function () {
var self = this
if (self.destroyed) return
self.destroy()
self._startReconnectTimer()
}
WebSocketTracker.prototype._onSocketError = function (err) {
var self = this
if (self.destroyed) return
self.destroy()
// errors will often happen if a tracker is offline, so don't treat it as fatal
self.client.emit('warning', err)
self._startReconnectTimer()
}
WebSocketTracker.prototype._startReconnectTimer = function () {
var self = this
var ms = Math.floor(Math.random() * RECONNECT_VARIANCE) + RECONNECT_MINIMUM
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self.reconnecting = true
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var reconnectTimer = setTimeout(function () {
self._openSocket()
}, ms)
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if (reconnectTimer.unref) reconnectTimer.unref()
debug('reconnecting socket in %s ms', ms)
}
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WebSocketTracker.prototype._send = function (params) {
var self = this
if (self.destroyed) return
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var message = JSON.stringify(params)
debug('send %s', message)
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self.socket.send(message)
}
WebSocketTracker.prototype._generateOffers = function (numwant, cb) {
var self = this
var offers = []
debug('generating %s offers', numwant)
for (var i = 0; i < numwant; ++i) {
generateOffer()
}
function generateOffer () {
var offerId = hat(160)
debug('creating peer (from _generateOffers)')
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var peer = self.peers[offerId] = new Peer({
initiator: true,
trickle: false,
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config: self.client._rtcConfig,
wrtc: self.client._wrtc
})
peer.once('signal', function (offer) {
offers.push({
offer: offer,
offer_id: common.hexToBinary(offerId)
})
checkDone()
})
peer.trackerTimeout = setTimeout(function () {
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debug('tracker timeout: destroying peer')
peer.trackerTimeout = null
delete self.peers[offerId]
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peer.destroy()
}, OFFER_TIMEOUT)
}
function checkDone () {
if (offers.length === numwant) {
debug('generated %s offers', numwant)
cb(offers)
}
}
}
function noop () {}