140 lines
4.5 KiB
Markdown
140 lines
4.5 KiB
Markdown
# ut_metadata [](https://travis-ci.org/feross/ut_metadata) [](https://npmjs.org/package/ut_metadata) [](https://www.gittip.com/feross/)
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### BitTorrent Extension for Peers to Send Metadata Files (BEP 9)
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[](https://ci.testling.com/feross/ut_metadata)
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Node.js implementation of the [Extension for Peers to Send Metadata Files (BEP 9)](http://www.bittorrent.org/beps/bep_0009.html). Use with [bittorrent-protocol](https://github.com/feross/bittorrent-protocol).
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The purpose of this extension is to allow clients to join a swarm and complete a download without the need of downloading a .torrent file first. This extension instead allows clients to download the metadata from peers. It makes it possible to support magnet links, a link on a web page only containing enough information to join the swarm (the info hash).
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Works in the browser with [browserify](http://browserify.org/)! This module is used by [WebTorrent](http://webtorrent.io).
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### install
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```
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npm install ut_metadata
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```
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### usage
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This package should be used with [bittorrent-protocol](https://github.com/feross/bittorrent-protocol), which supports a plugin-like system for extending the protocol with additional functionality.
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Say you're already using `bittorrent-protocol`. Your code might look something like this:
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```js
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var Protocol = require('bittorrent-protocol')
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var net = require('net')
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net.createServer(function (socket) {
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var wire = new Protocol()
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socket.pipe(wire).pipe(socket)
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// handle handshake
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wire.on('handshake', function (infoHash, peerId) {
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wire.handshake(new Buffer('my info hash'), new Buffer('my peer id'))
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})
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}).listen(6881)
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```
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To add support for BEP 9, simply modify your code like this:
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```js
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var Protocol = require('bittorrent-protocol')
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var net = require('net')
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var ut_metadata = require('ut_metadata')
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net.createServer(function (socket) {
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var wire = new Protocol()
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socket.pipe(wire).pipe(socket)
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// initialize the extension
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wire.use(ut_metadata())
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// all `ut_metadata` functionality can now be accessed at wire.ut_metadata
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// ask the peer to send us metadata
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wire.ut_metadata.fetch()
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// 'metadata' event will fire when the metadata arrives and is verified to be correct!
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wire.ut_metadata.on('metadata', function (metadata) {
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// got metadata!
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// Note: the event will not fire if the peer does not support ut_metadata, if they
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// don't have metadata yet either, if they repeatedly send invalid data, or if they
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// simply don't respond.
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})
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// optionally, listen to the 'warning' event if you want to know that metadata is
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// probably not going to arrive for one of the above reasons.
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wire.ut_metadata.on('warning', function (err) {
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console.log(err.message)
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})
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// handle handshake
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wire.on('handshake', function (infoHash, peerId) {
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wire.handshake(new Buffer('my info hash'), new Buffer('my peer id'))
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})
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}).listen(6881)
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```
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### api
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#### `ut_metadata([metadata])`
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Initialize the extension. If you have the torrent metadata (Buffer), pass it into the
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`ut_metadata` constructor so it's made available to the peer.
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```js
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var metadata = fs.readFileSync(__dirname + '/file.torrent')
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wire.use(ut_metadata(metadata))
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```
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#### `ut_metadata.fetch()`
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Ask the peer to send metadata.
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#### `ut_metadata.cancel()`
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Stop asking the peer to send metadata.
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#### `ut_metadata.setMetadata(metadata)`
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Set the metadata. If you didn't have the metadata at the time `ut_metadata` was
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initialized, but you end up getting it from another peer (or somewhere else), you should
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call `setMetadata` so the metadata will be available to the peer.
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#### `ut_metadata.on('metadata', function (metadata) {})`
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Fired when metadata is available and verified to be correct. Called with a single
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parameter of type Buffer.
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```js
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wire.ut_metadata.on('metadata', function (metadata) {
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console.log(Buffer.isBuffer(metadata)) // true
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})
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```
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Note: the event will not fire if the peer does not support ut_metadata, if they
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don't have metadata yet either, if they repeatedly send invalid data, or if they
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simply don't respond.
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#### `ut_metadata.on('warning', function (err) {})`
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Fired if:
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- the peer does not support ut_metadata
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- the peer doesn't have metadata yet
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- the peer repeatedly sent invalid data
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```js
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wire.ut_metadata.on('warning', function (err) {
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console.log(err.message)
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})
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```
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### license
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MIT. Copyright (c) [Feross Aboukhadijeh](http://feross.org).
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