it-mplex

JavaScript implementation of mplex.

Install

npm install it-mplex

Usage

const Mplex = require('it-mplex')
const pipe = require('it-pipe')

const muxer = new Mplex({
  onStream: stream => { // Receive a duplex stream from the remote
    // ...receive data from the remote and optionally send data back
  }
})

pipe(conn, muxer, conn) // conn is duplex connection to another peer

const stream = muxer.newStream() // Create a new duplex stream to the remote

// Use the duplex stream to send some data to the remote...
pipe([1, 2, 3], stream)

API

const muxer = new Mplex([options])

Create a new duplex stream that can be piped together with a connection in order to allow multiplexed communications.

e.g.

const Mplex = require('it-mplex')
const pipe = require('it-pipe')

// Create a duplex muxer
const muxer = new Mplex()

// Use the muxer in a pipeline
pipe(conn, muxer, conn) // conn is duplex connection to another peer

options is an optional Object that may have the following properties:

• onStream - A function called when receiving a new stream from the remote. e.g.

  // Receive a new stream on the muxed connection
  const onStream = stream => {
    // Read from this stream and write back to it (echo server)
    pipe(
      stream,
      source => (async function * () {
        for await (const data of source) yield data
      })(),
      stream
    )
  }
  const muxer = new Mplex({ onStream })
  // ...

  Note: The onStream function can be passed in place of the options object. i.e.

  new Mplex(stream => { /* ... */ })

• signal - An AbortSignal which can be used to abort the muxer, including all of it's multiplexed connections. e.g.

  const controller = new AbortController()
  const muxer = new Mplex({ signal: controller.signal })
  
  pipe(conn, muxer, conn)
  
  controller.abort()

• maxMsgSize - The maximum size in bytes the data field of multiplexed messages may contain (default 1MB)

muxer.onStream

Use this property as an alternative to passing onStream as an option to the Mplex constructor.

const stream = muxer.newStream([options])

Initiate a new stream with the remote. Returns a duplex stream.

e.g.

// Create a new stream on the muxed connection
const stream = muxer.newStream()

// Use this new stream like any other duplex stream:
pipe([1, 2, 3], stream, consume)

In addition to sink and source properties, this stream also has the following API, that will normally not be used by stream consumers.

stream.close()

Closes the stream for reading. If iterating over the source of this stream in a for await of loop, it will return (exit the loop) after any buffered data has been consumed.

This function is called automatically by the muxer when it receives a CLOSE message from the remote.

The source will return normally, the sink will continue to consume.

stream.abort([err])

Closes the stream for reading and writing. This should be called when a local error has occurred.

Note, if called without an error any buffered data in the source can still be consumed and the stream will end normally.

This will cause a RESET message to be sent to the remote, unless the sink has already ended.

The sink will return and the source will throw if an error is passed or return normally if not.

stream.reset()

Closes the stream immediately for reading and writing. This should be called when a remote error has occurred.

This function is called automatically by the muxer when it receives a RESET message from the remote.

The sink will return and the source will throw.