multiplex-demultiplex object streams across any text stream.

Build Status


Stable: Expect patches, possible features additions.


var MuxDemux = require('mux-demux')
var net = require('net')

net.createServer(function (con) {
  con.pipe(MuxDemux(function (stream) {
    stream.on('data', console.log.bind(console))
}).listen(8642, function () {
  var con = net.connect(8642), mx
  con.pipe(mx = MuxDemux()).pipe(con)

  var ds = mx.createWriteStream('times')

  setInterval(function () {
    ds.write(new Date().toString())
  }, 1e3)

Binary Support

By encoding JSON as msgpack, binary is supported. just require from mux-demux/msgpack instead of mux-demux.

var MuxDemux = require('mux-demux/msgpack')


take care to create a MuxDemux instance per connection, do not connect many connections to one `MuxDemux'.


net.createServer(function (stream) {
  stream.pipe(MuxDemux(function (_stream) {



var mx = MuxDemux()
net.createServer(function (stream) {
  //this will connect many streams to the OUTER MuxDemux Stream!


var mx = MuxDemux()
mx.close(function () {
  console.log("connection close");

var A = mx.createStream()


var mx = MuxDemux()

var A = mx.createStream()

mx.close(function () {
  console.log("connection close");

actually this will not close mx

Errors, and use in PRODUCTION

mux-demux parses a JSON protocol, and so you must handle any errors that may result from someone connecting, and sending invalid data.

net.createServer(function (stream) {
  var mx = MuxDemux()
  mx.on('error', function () {
  stream.on('error', function () {


the API browser-stream

var MuxDemux = require('mux-demux')
var a = MuxDemux()
var b = MuxDemux()


b.on('connection', function (stream) {
  // inspect stream.meta to decide what this stream is.


there is actually no distinction between clients and servers. if both sides are listening on('connection',...) then both sides may call create{Write,Read,}Stream(meta) and initiate new streams.

MuxDemux(options, onConnection)

Creates a MuxDemux stream. Optionally pass in an options hash

    error: Boolean,
    wrapper: function (stream) {...}

If the error option is set to true then MuxDemux will emit errors on the streams on unexpected disconnects. othewise, it will just emit 'end' on those streams.

wrapper be used to change the serialization format used by mux-demux, by default, line seperated json is used. see examples below both mux-demux end points must use the same wrapper.

options is optional. MuxDemux(onConnection) is a shortcut for MuxDemux().on('connection', onConnection)

createReadStream (meta)

open a ReadableStream from the other side. returns a ReadableStream. the other side of connection will emit a writable stream that is connected to this stream.

createWriteStream (meta)

open a WritableStream to the other side. returns a WritableStream, the other side will emit a ReadableStream connected to this stream.

createStream (meta, opts)

open a Stream to the other side which is both readable and writable. returns a Stream, the other side will emit a Stream connected to this stream.

opts may be {allowHalfOpen: true}, if this is not set, the stream will emit 'end' when end() is called. this may cause the stream to loose some data from the other end. If allowHalfOpen is true then the remote end must call end().

note to self, references to a class (Stream) should be capitalized, and in backticks. references to an instance should be lowercase, and not in backticks unless refuring to a specific variable in a code example.


asks mux-demux to emit end once all the sub-streams have closed. this will wait untill they have ended, closed, or errored, just like net.Server#close.

Takes an optional callback, and emits the 'end' event.

Wrapper Examples

A stream of plain old js objects.

new MuxDemux({wrapper: function (stream) { return stream } })

A stream of msgpack.

var es = require('event-stream')
var ms = require('msgpack-stream')

new MuxDemux({wrapper: function (stream) {
  return es.pipeline(ms.createDecodeStream(), stream, ms.createEncodeStream())


there is one addition to the stream interface. call stream.error(err) will send an error that will be emitted at the other side of the stream. this is useful for sending 404 like messages to clients, etc.