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https://github.com/webtorrent/bittorrent-protocol

Simple, robust, BitTorrent peer wire protocol implementation
https://github.com/webtorrent/bittorrent-protocol

bittorrent browser javascript nodejs p2p protocol torrent webtorrent

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Simple, robust, BitTorrent peer wire protocol implementation

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# bittorrent-protocol [![travis][travis-image]][travis-url] [![npm][npm-image]][npm-url] [![downloads][downloads-image]][downloads-url] [![javascript style guide][standard-image]][standard-url]



[travis-image]: https://img.shields.io/travis/webtorrent/bittorrent-protocol/master.svg

[travis-url]: https://travis-ci.org/webtorrent/bittorrent-protocol

[npm-image]: https://img.shields.io/npm/v/bittorrent-protocol.svg

[npm-url]: https://npmjs.org/package/bittorrent-protocol

[downloads-image]: https://img.shields.io/npm/dm/bittorrent-protocol.svg

[downloads-url]: https://npmjs.org/package/bittorrent-protocol

[standard-image]: https://img.shields.io/badge/code_style-standard-brightgreen.svg

[standard-url]: https://standardjs.com



### Simple, robust, BitTorrent wire protocol implementation



Node.js implementation of the [BitTorrent peer wire protocol](https://wiki.theory.org/BitTorrentSpecification#Peer_wire_protocol_.28TCP.29).

The protocol is the main communication layer for BitTorrent file transfer.



Also works in the browser with [browserify](http://browserify.org/)! This module is used

by [WebTorrent](http://webtorrent.io).



## install



```

npm install bittorrent-protocol

```



## usage



The protocol is implemented as a **duplex stream**, so all you have to do is pipe to and

from it.



duplex streams | a.pipe(b).pipe(a)

---- | ---

![duplex streams](https://raw.github.com/substack/lxjs-stream-examples/master/images/duplex_streams.png) | ![a.pipe(b).pipe(a)](https://raw.github.com/substack/lxjs-stream-examples/master/images/a_pipe_b_pipe_a.png)



(Images from the ["harnessing streams"](https://github.com/substack/lxjs-stream-examples/blob/master/slides.markdown) talk by substack.)



```js

import Protocol from 'bittorrent-protocol'

import net from 'net'



net.createServer(socket => {

	const wire = new Protocol()



	// pipe to and from the protocol

	socket.pipe(wire).pipe(socket)



	wire.on('handshake', (infoHash, peerId) => {

    // receive a handshake (infoHash and peerId are hex strings)



		// lets emit a handshake of our own as well

		wire.handshake('my info hash (hex)', 'my peer id (hex)')

	})



	wire.on('unchoke', () => {

		console.log('peer is no longer choking us: ' + wire.peerChoking)

	})

}).listen(6881)

```



## methods



### handshaking



Send and receive a handshake from the peer. This is the first message.



```js

// send a handshake to the peer

wire.handshake(infoHash, peerId, { dht: true })

wire.on('handshake', (infoHash, peerId, extensions) => {

	// receive a handshake (infoHash and peerId are hex strings)

  console.log(extensions.dht) // supports DHT (BEP-0005)

  console.log(extensions.extended) // supports extension protocol (BEP-0010)

})

```



For `wire.handshake()`, the `infoHash` and the `peerId` should be 20 bytes (hex-encoded `string` or `Buffer`).



### choking



Check if you or the peer is choking.



```js

wire.peerChoking // is the peer choking us?

wire.amChoking // are we choking the peer?



wire.on('choke', () => {

	// the peer is now choking us

})

wire.on('unchoke', () => {

	// peer is no longer choking us

})

```



### interested



See if you or the peer is interested.



```js

wire.peerInterested // is the peer interested in us?

wire.amInterested // are we interested in the peer?



wire.on('interested', () => {

	// peer is now interested

})

wire.on('uninterested', () => {

	// peer is no longer interested

})

```



### bitfield



Exchange piece information with the peer.



```js

// send a bitfield to the peer

wire.bitfield(buffer)

wire.on('bitfield', bitfield => {

	// bitfield received from the peer

})



// send a have message indicating that you have a piece

wire.have(pieceIndex)

wire.on('have', pieceIndex => {

	// peer has sent you a have message

})

```



You can always see which pieces the peer has



```js

wire.peerPieces.get(i) // returns true if peer has piece i

```



`wire.peerPieces` is a `BitField`, see [docs](https://www.npmjs.org/package/bitfield).



### requests



Send and respond to requests for pieces.



```js

// request a block from a peer

wire.request(pieceIndex, offset, length, (err, block) => {

	if (err) {

		// there was an error (peer has started choking us etc)

		return

	}

	// got block

})



// cancel a request to a peer

wire.cancel(pieceIndex, offset, length)



// receive a request from a peer

wire.on('request', (pieceIndex, offset, length, callback) => {

	// ... read block ...

	callback(null, block) // respond back to the peer

})



wire.requests     // list of requests we currently have pending {piece, offset, length}

wire.peerRequests // list of requests the peer currently have pending {piece, offset, length}

```



You can set a request timeout if you want to.



```js

wire.setTimeout(5000) // head request should take a most 5s to finish

```



If the timeout is triggered the request callback is called with an error and a `timeout`

event is emitted.



### dht and port



You can set the extensions flag `dht` in the handshake to `true` if you participate in

the torrent dht. Afterwards you can send your dht port.



```js

// send your port to the peer

wire.port(dhtPort)

wire.on('port', dhtPort => {

	// peer has sent a port to us

})

```



You can check to see if the peer supports extensions.



```js

wire.peerExtensions.dht // supports DHT (bep_0005)

wire.peerExtensions.extended // supports extended messages (bep_0005)

```



### keep-alive



You can enable the keep-alive ping (triggered every 60s).



```js

// starts the keep alive

wire.setKeepAlive(true)

wire.on('keep-alive', () => {

	// peer sent a keep alive - just ignore it

})

```

### fast extension (BEP 6)



This module has built-in support for the

[BitTorrent Fast Extension (BEP 6)](http://www.bittorrent.org/beps/bep_0006.html).



The Fast Extension introduces several messages to make the protocol more efficient:

have-none, have-all, suggest, reject, and allowed-fast.



```js

wire.handshake(infoHash, peerId, { fast: true })



wire.hasFast // true if Fast Extension is available, required to call the following methods



wire.haveNone() // instead of wire.bitfield(buffer) with an all-zero buffer

wire.on('have-none', () => {

  // instead of bitfield with an all-zero buffer

})



wire.haveAll() // instead of wire.bitfield(buffer) with an all-one buffer

wire.on('have-all', () => {

  // instead of bitfield with an all-one buffer

})



wire.suggest(pieceIndex) // suggest requesting a piece to the peer

wire.on('suggest', (pieceIndex) => {

  // peer suggests requesting piece

})



wire.on('allowed-fast', (pieceIndex) => {

  // piece may be obtained from peer while choked

})



wire.peerAllowedFastSet // list of allowed-fast pieces



// Note rejection is handled automatically on choke or request error

wire.reject(pieceIndex, offset, length) // reject a request

wire.on('reject', (pieceIndex, offset, length) => {

  // peer rejected a request

})

```



### extension protocol (BEP 10)



This module has built-in support for the

[BitTorrent Extension Protocol (BEP 10)](http://www.bittorrent.org/beps/bep_0010.html).



The intention of BEP 10 is to provide a simple and thin transport for extensions to the

bittorrent protocol. Most extensions to the protocol use BEP 10 so they can add new

features to the protocol without interfering with the standard bittorrent protocol or

clients that don't support the new extension.



An example of a BitTorrent extension that uses BEP 10 is

[ut_metadata](http://www.bittorrent.org/beps/bep_0009.html) (BEP 9), the extension that

allows magnet uris to work.



```js

wire.extended(code, buffer)

```



This package, **bittorrent-protocol**, also provides an extension API to make it easy to

add extensions to this module using the "extension protocol" (BEP 10). For example, to

support ut_metadata (BEP 9), you need only install the

[ut_metadata](https://www.npmjs.com/package/ut_metadata) npm module and call `wire.use()`.

See the [Extension API](#extension-api) section for more information.



### transfer stats



Check how many bytes you have uploaded and download, and current speed



```js

wire.uploaded // number of bytes uploaded

wire.downloaded // number of bytes downloaded



wire.uploadSpeed() // upload speed - bytes per second

wire.downloadSpeed() // download speed - bytes per second



wire.on('download', numberOfBytes => {

  ...

})

wire.on('upload', numberOfBytes => {

  ...

})

```



## extension api



This package supports a simple extension API so you can extend the default protocol

functionality with common protocol extensions like ut_metadata (magnet uris).



Here are the **bittorrent-protocol** extensions that we know about:



- [ut_metadata](https://www.npmjs.com/package/ut_metadata) - Extension for Peers to Send Metadata Files (BEP 9)

- [ut_pex](https://www.npmjs.com/package/ut_pex) - Extension for Peer Discovery (PEX)

- *Add yours here! Send a pull request!*



In short, an extension can register itself with at a certain name, which will be added to

the extended protocol handshake sent to the remote peer. Extensions can also hook events

like 'handshake' and 'extended'. To use an extension, simply require it and call

`wire.use()`.



Here is an example of the **ut_metadata** extension being used with

**bittorrent-protocol**:



```js

import Protocol from 'bittorrent-protocol'

import net from 'net'

import ut_metadata from 'ut_metadata'



net.createServer(socket => {

  const wire = new Protocol()

  socket.pipe(wire).pipe(socket)



  // initialize the extension

  wire.use(ut_metadata())



  // all `ut_metadata` functionality can now be accessed at wire.ut_metadata



  // ask the peer to send us metadata

  wire.ut_metadata.fetch()



  // 'metadata' event will fire when the metadata arrives and is verified to be correct!

  wire.ut_metadata.on('metadata', metadata => {

    // got metadata!



    // Note: the event will not fire if the peer does not support ut_metadata, if they

    // don't have metadata yet either, if they repeatedly send invalid data, or if they

    // simply don't respond.

  })



  // optionally, listen to the 'warning' event if you want to know that metadata is

  // probably not going to arrive for one of the above reasons.

  wire.ut_metadata.on('warning', err => {

    console.log(err.message)

  })



  // handle handshake

  wire.on('handshake', (infoHash, peerId) => {

    // receive a handshake (infoHash and peerId are hex strings)

    wire.handshake(new Buffer('my info hash'), new Buffer('my peer id'))

  })



}).listen(6881)

```



If you want to write your own extension, take a look at the

[ut_metadata index.js file](https://github.com/webtorrent/ut_metadata/blob/master/index.js)

to see how it's done.



## license



MIT. Copyright (c) [Feross Aboukhadijeh](https://feross.org), Mathias Buus, and [WebTorrent, LLC](https://webtorrent.io).