lt_donthave
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The BitTorrent lt_donthave extension (BEP 54)
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JavaScript implementation of the [The BitTorrent lt_donthave extension (BEP 54)](https://www.bittorrent.org/beps/bep_0054.html). Use with [bittorrent-protocol](https://www.npmjs.com/package/bittorrent-protocol).
The purpose of this extension is to allow peers to indicate that they no longer have a piece. It provides a single `donthave` message that means the opposite of the standard `have` message. In addition, when a client receives `donthave`, it knows that all requests for the matching piece have failed.
Works in the browser with [browserify](http://browserify.org/)! This module is used by [WebTorrent](http://webtorrent.io).
### install
```
npm install lt_donthave
```
### usage
This package should be used with [bittorrent-protocol](https://www.npmjs.com/package/bittorrent-protocol), which supports a plugin-like system for extending the protocol with additional functionality.
Say you're already using `bittorrent-protocol`. Your code might look something like this:
```js
import BitField from 'bitfield'
import Protocol from 'bittorrent-protocol'
import net from 'net'
net.createServer(socket => {
var wire = new Protocol()
socket.pipe(wire).pipe(socket)
// handle handshake
wire.on('handshake', (infoHash, peerId) => {
wire.handshake(Buffer.from('my info hash'), Buffer.from('my peer id'))
// advertise that we have all 10 pieces of the torrent
const bitfield = new BitField(10)
for (let i = 0; i <= 10; i++) {
bitfield.set(i, true)
}
wire.bitfield(bitfield)
})
}).listen(6881)
```
To add support for BEP 54, simply modify your code like this:
```js
import BitField from 'bitfield'
import Protocol from 'bittorrent-protocol'
import net from 'net'
import lt_donthave from 'lt_donthave'
net.createServer(socket => {
const wire = new Protocol()
socket.pipe(wire).pipe(socket)
// initialize the extension
wire.use(lt_donthave())
// all `lt_donthave` functionality can now be accessed at wire.lt_donthave
wire.on('request', (pieceIndex, offset, length, cb) => {
// whoops, turns out we don't have any pieces after all
wire.lt_donthave.donthave(pieceIndex)
cb(new Error('not found'))
})
// 'donthave' event will fire when the remote peer indicates it no longer has a piece
wire.lt_donthave.on('donthave', index => {
// remote peer no longer has piece `index`
})
// handle handshake
wire.on('handshake', (infoHash, peerId) => {
wire.handshake(Buffer.from('my info hash'), Buffer.from('my peer id'))
// advertise that we have all 10 pieces of the torrent
const bitfield = new BitField(10)
for (let i = 0; i <= 10; i++) {
bitfield.set(i, true)
}
wire.bitfield(bitfield)
})
}).listen(6881)
```
Initialize the extension.
```js
wire.use(lt_donthave())
```
Tell the remote peer that this peer no longer has the piece with the specified `index`.
Opposite of `wire.have`.
Fired when the remote peer no longer has the piece with the specified `index`.
Opposite of `wire.on('have', index => ())`
After this is fired, all outstanding requests to the remote peer for that piece will automatically fail.
MIT. Copyright (c) John Hiesey and [WebTorrent, LLC](https://webtorrent.io).