Nondeterministic Postrequisite Metaprotocol

    ut_pex

    3.0.1 • Public • Published

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    BitTorrent Extension for Peer Discovery (PEX) (BEP11)

    Node.js implementation of the ut_pex protocol (BEP11), which is the most popular PEX (peer exchange) protocol used by bittorrent clients.

    The purpose of this extension is to allow peers to exchange known peers directly with each other, thereby facilitating more efficient peer discovery and healthier swarms.

    The best description of the (nonstandardized) ut_pex protocol I could find is in section 2.1.4.3 of this paper.

    Works in the browser with browserify! This module is used by WebTorrent.

    install

    npm install ut_pex
    

    usage

    This package should be used with 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:

    const Protocol = require('bittorrent-protocol')
    const net = require('net')
    
    net.createServer(socket => {
      const wire = new Protocol()
      socket.pipe(wire).pipe(socket)
    
      // handle handshake
      wire.on('handshake', (infoHash, peerId) => {
        wire.handshake(new Buffer('my info hash'), new Buffer('my peer id'))
      })
    
    }).listen(6881)

    To add support for PEX, simply modify your code like this:

    const Protocol = require('bittorrent-protocol')
    const net = require('net')
    const ut_pex = require('ut_pex')
    
    net.createServer(socket => {
      const wire = new Protocol()
      socket.pipe(wire).pipe(socket)
    
      // initialize the extension
      wire.use(ut_pex())
    
      // all `ut_pex` functionality can now be accessed at wire.ut_pex
    
      // (optional) start sending peer information to remote peer
      wire.ut_pex.start()
    
      // 'peer' event will fire for every new peer sent by the remote peer
      wire.ut_pex.on('peer', (peer, flags) => {
        // got a peer
        // probably add it to peer connections queue
      })
    
      // handle handshake
      wire.on('handshake', (infoHash, peerId) => {
        wire.handshake(new Buffer('my info hash'), new Buffer('my peer id'))
      })
    
    }).listen(6881)

    methods

    start

    Start sending regular PEX updates to the remote peer. Use addPeer and dropPeer to control the content of PEX messages. PEX messages will be sent once every ~65 seconds.

    wire.ut_pex.start()

    Note that ut_pex may be used for one-way peer discovery without sending PEX updates to the remote peer, but this use case is discouraged because PEX, like bittorrent is more efficient through altruism.

    stop

    Stop sending PEX updates to the remote peer.

    wire.ut_pex.stop()

    reset

    Stops sending updates to the remote peer and resets internal state of peers seen.

    wire.ut_pex.reset()

    addPeer

    Adds an IPv4 peer to the locally discovered peer list to send with the next PEX message.

    const peer = '127.0.0.1:6889'
    const flags = {
      prefersEncryption: false,
      isSender: true,
      supportsUtp: true,
      supportsUtHolepunch: false,
      isReachable: false
    }
    
    wire.ut_pex.addPeer(peer, flags)

    addPeer6

    Adds an IPv6 peer to the locally discovered peer list to send with the next PEX message.

    const peer = '[::1]:6889'
    const flags = {
      prefersEncryption: false,
      isSender: true,
      supportsUtp: true,
      supportsUtHolepunch: false,
      isReachable: false
    }
    
    wire.ut_pex.addPeer6(peer, flags)

    dropPeer

    Adds an IPv4 peer to the locally dropped peer list to send with the next PEX message.

    wire.ut_pex.dropPeer('127.0.0.1:6889')

    dropPeer6

    Adds an IPv6 peer to the locally dropped peer list to send with the next PEX message.

    wire.ut_pex.dropPeer6('[::1]:6889')

    events

    event: 'peer'

    Fired for every new peer received from PEX.

    wire.ut_pex.on('peer', (peer, flags) => {
      const parts = peer.split(':')
      const ip = parts[0]
      const port = parts[1]
      // ...
    })

    Note: the event will not fire if the peer does not support ut_pex or if they don't respond.

    event: 'dropped'

    Fired for every peer dropped from the swarm notified via PEX.

    wire.ut_pex.on('dropped', peer => {
      const parts = peer.split(':')
      const ip = parts[0]
      const port = parts[1]
      // ...
    })

    Note: the event will not fire if the peer does not support ut_pex or if they don't respond.

    flags

    In order to handle ut_pex protocol (BEP11) bit-flags in a more humand friendly format, the given boolean based Object has been defined.

    const flags = {
      prefersEncryption: Boolean,
      isSender: Boolean,
      supportsUtp: Boolean,
      supportsUtHolepunch: Boolean,
      isReachable: Boolean
    }

    license

    MIT. Copyright (c) Travis Fischer and WebTorrent, LLC

    Install

    npm i ut_pex

    DownloadsWeekly Downloads

    3,471

    Version

    3.0.1

    License

    MIT

    Unpacked Size

    16.4 kB

    Total Files

    4

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