movable-stream

What?

This module is a duplex stream, like a regular socket, which wraps some, other underlying duplex stream. You use one instance to wrap each end of the underlying stream, and it allows you to replace the underlying stream, while data is flowing, without the code using the movable stream noticing that anything changed.

It switches streams... midstream.

Why?

Say you want to send data between two browsers using WebRTC data channels. You already need to connect to a signaling server (using e.g. websockets) to open a WebRTC connection in the first place, and it takes a little while for the WebRTC connection to open.

Instead of waiting for the connection to open before sending data, you can set up a stream multiplexed on top of the websockets you already have that forwards data from browser <-> server <-> browser. You are using the server, temporarily, as a relay. Once the WebRTC connection is open, you can transparently replace the relayed connection with the brand-new WebRTC connection, all without the code using the stream noticing anything changed at all!

Example

let Movable = require('movable-stream')

let originalStream = ... // whatever stream you want wrap initially (e.g. over websockets)

let ms = new Movable(originalStream)

// now ms is readable and writable
ms.on('data', (chunk) => {
  console.log('Received ${chunk.length} bytes of data.');
});

ms.write('hello, world!')

let newStream = ... // a replacement for originalStream (e.g. WebRTC data channel stream)

ms.on('moved', () => {
	originalStream.destroy() // original stream is no longer needed
})
ms.replace(newStream) // data starts flowing over newStream instead of originalStream, transparently

License

MIT