multistream-select

    2.0.1 • Public • Published

    js-multistream-select

    Dependency Status js-standard-style

    JavaScript implementation of multistream-select

    Lead Maintainer

    Jacob Heun

    Table of Contents

    Background

    What is multistream-select?

    TLDR; multistream-select is protocol multiplexing per connection/stream. Full spec here

    Select a protocol flow

    The caller will send "interactive" messages, expecting for some acknowledgement from the callee, which will "select" the handler for the desired and supported protocol:

    < /multistream-select/0.3.0  # i speak multistream-select/0.3.0
    > /multistream-select/0.3.0  # ok, let's speak multistream-select/0.3.0
    > /ipfs-dht/0.2.3            # i want to speak ipfs-dht/0.2.3
    < na                         # ipfs-dht/0.2.3 is not available
    > /ipfs-dht/0.1.9            # What about ipfs-dht/0.1.9 ?
    < /ipfs-dht/0.1.9            # ok let's speak ipfs-dht/0.1.9 -- in a sense acts as an ACK
    > <dht-message>
    > <dht-message>
    > <dht-message>

    This mode also packs a ls option, so that the callee can list the protocols it currently supports

    Install

    npm i multistream-select

    Usage

    const MSS = require('multistream-select')
    // You can now use
    // MSS.Dialer - actively select a protocol with a remote
    // MSS.Listener - handle a protocol with a remote

    Dialer

    const pipe = require('it-pipe')
    const MSS = require('multistream-select')
    const Mplex = require('libp2p-mplex')
    
    const muxer = new Mplex()
    const muxedStream = muxer.newStream()
    
    const mss = new MSS.Dialer(muxedStream)
    
    // mss.select(protocol(s))
    // Select from one of the passed protocols (in priority order)
    // Returns selected stream and protocol
    const { stream: dhtStream, protocol } = await mss.select([
      // This might just be different versions of DHT, but could be different impls
      '/ipfs-dht/2.0.0', // Most of the time this will probably just be one item.
      '/ipfs-dht/1.0.0'
    ])
    
    // Typically this stream will be passed back to the caller of libp2p.dialProtocol
    //
    // ...it might then do something like this:
    // try {
    //   await pipe(
    //     [uint8ArrayFromString('Some DHT data')]
    //     dhtStream,
    //     async source => {
    //       for await (const chunk of source)
    //         // DHT response data
    //     }
    //   )
    // } catch (err) {
    //   // Error in stream
    // }

    Listener

    const pipe = require('it-pipe')
    const MSS = require('multistream-select')
    const Mplex = require('libp2p-mplex')
    
    const muxer = new Mplex({
      async onStream (muxedStream) {
        const mss = new MSS.Listener(muxedStream)
    
        // mss.handle(handledProtocols)
        // Returns selected stream and protocol
        const { stream, protocol } = await mss.handle([
          '/ipfs-dht/1.0.0',
          '/ipfs-bitswap/1.0.0'
        ])
    
        // Typically here we'd call the handler function that was registered in
        // libp2p for the given protocol:
        // e.g. handlers[protocol].handler(stream)
        //
        // If protocol was /ipfs-dht/1.0.0 it might do something like this:
        // try {
        //   await pipe(
        //     dhtStream,
        //     source => (async function * () {
        //       for await (const chunk of source)
        //         // Incoming DHT data -> process and yield to respond
        //     })(),
        //     dhtStream
        //   )
        // } catch (err) {
        //   // Error in stream
        // }
      }
    })

    API

    new MSS.Dialer(duplex)

    Create a new multistream select "dialer" instance which can be used to negotiate a protocol to use, list all available protocols the remote supports, or do both.

    Parameters

    Returns

    A new multistream select dialer instance.

    Examples

    const dialer = new MSS.Dialer(duplex)

    dialer.select(protocols)

    Negotiate a protocol to use from a list of protocols.

    Parameters

    • protocols (String[]/String) - A list of protocols (or single protocol) to negotiate with. Protocols are attempted in order until a match is made.

    Returns

    Promise<{ stream<Object>, protocol<String> }> - A stream for the selected protocol and the protocol that was selected from the list of protocols provided to select.

    Note that after a protocol is selected dialer can no longer be used.

    Examples

    const { stream, protocol } = await dialer.select([
      // This might just be different versions of DHT, but could be different impls
      '/ipfs-dht/2.0.0', // Most of the time this will probably just be one item.
      '/ipfs-dht/1.0.0'
    ])
    // Now talk `protocol` on `stream`

    dialer.ls()

    List protocols that the remote supports.

    Returns

    String[] - A list of all the protocols the remote supports.

    Examples

    const protocols = await dialer.ls()
    const wantedProto = '/ipfs-dht/2.0.0'
    
    if (!protocols.includes(wantedProto)) {
      throw new Error('remote does not support ' + wantedProto)
    }
    
    // Now use dialer.select to use wantedProto, safe in the knowledge it is supported

    new MSS.Listener(duplex)

    Construct a new multistream select "listener" instance which can be used to handle multistream protocol selections for particular protocols.

    Parameters

    Returns

    A new multistream select listener instance.

    Examples

    const listener = new MSS.Listener(duplex)

    listener.handle(protocols)

    Handle multistream protocol selections for the given list of protocols.

    Parameters

    • protocols (String[]/String) - A list of protocols (or single protocol) that this listener is able to speak.

    Returns

    Promise<{ stream<Object>, protocol<String> }> - A stream for the selected protocol and the protocol that was selected from the list of protocols provided to select.

    Note that after a protocol is handled listener can no longer be used.

    Examples

    const { stream, protocol } = await listener.handle([
      '/ipfs-dht/1.0.0',
      '/ipfs-bitswap/1.0.0'
    ])
    // Remote wants to speak `protocol`

    Contribute

    Contributions welcome. Please check out the issues.

    Check out our contributing document for more information on how we work, and about contributing in general. Please be aware that all interactions related to multiformats are subject to the IPFS Code of Conduct.

    Small note: If editing the README, please conform to the standard-readme specification.

    License

    MIT

    Install

    npm i multistream-select

    DownloadsWeekly Downloads

    18,497

    Version

    2.0.1

    License

    MIT

    Unpacked Size

    83 kB

    Total Files

    10

    Last publish

    Collaborators

    • jacobheun
    • daviddias
    • vascosantos