add readme

Author: feross

README.md

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+# bittorrent-tracker [![build](http://img.shields.io/travis/feross/bittorrent-tracker.svg)](https://travis-ci.org/feross/bittorrent-tracker) [![npm](http://img.shields.io/npm/v/bittorrent-tracker.svg)](https://npmjs.org/package/bittorrent-tracker) [![gittip](http://img.shields.io/gittip/feross.svg)](https://www.gittip.com/feross/)
+
+### Simple, robust, BitTorrent tracker (client & server) implementation
+
+Node.js implementation of a [BitTorrent tracker](https://wiki.theory.org/BitTorrentSpecification#Tracker_HTTP.2FHTTPS_Protocol), client and server.
+
+A **BitTorrent tracker** is an HTTP service which responds to GET requests from BitTorrent
+clients. The requests include metrics from clients that help the tracker keep overall
+statistics about the torrent. The response includes a peer list that helps the client
+participate in the torrent.
+
+Also see [BitTorrent DHT](https://github.com/feross/bittorrent-dht). This module is used
+by [WebTorrent](http://webtorrent.io).
+
+## install
+
+```
+npm install bittorrent-tracker
+```
+
+## usage
+
+To connect to a tracker, just do this:
+
+```js
+var Client = require('bittorrent-tracker').Client
+var parseTorrent = require('parse-torrent')
+
+var torrent = fs.readFileSync(__dirname + '/torrents/bitlove-intro.torrent')
+var parsedTorrent = parseTorrent(torrent) // { infoHash: 'xxx', length: xx, announce: ['xx', 'xx'] }
+
+var peerId = new Buffer('01234567890123456789')
+var port = 6881
+
+var client = new Client(peerId, port, parsedTorrent)
+
+// you must add an 'error' event handler!
+client.on('error', function (err) {
+  console.log(err.message)
+  // a tracker was unavailable or sent bad data to the client. you can probably ignore it
+})
+
+client.start() // start getting peers from the tracker
+
+client.on('update', function (data) {
+  console.log('got a response from tracker: ' + data.announce)
+  console.log('number of seeders on this tracker: ' + data.complete)
+  console.log('number of leechers on this tracker: ' + data.incomplete)
+})
+
+client.once('peer', function (addr) {
+  console.log('found a peer: ' + addr) // 85.10.239.191:48623
+})
+
+client.complete() // announce that download has completed (and you are now a seeder)
+
+client.update() // force a tracker announce. will trigger more 'update' events and maybe more 'peer' events
+
+client.stop() // stop getting peers from the tracker, gracefully leave the swarm
+```
+
+**TODO:** Add BitTorrent tracker server implementation!
+
+```js
+var Server = require('bittorrent-tracker').Server
+
+```
+
+## license
+
+MIT. Copyright (c) [Feross Aboukhadijeh](http://feross.org).