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Simple WebRTC video, voice, and data channels

<h5 align="center"> Sponsored by&nbsp;&nbsp;&nbsp;&nbsp;<a href="http://dfinity.org/"><img src="https://cdn.rawgit.com/feross/simple-peer/master/img/dfinity-sponsor.png" alt="DFINITY" width=250 valign="middle"></a> </h5>

We are hiring a peer-to-peer WebRTC mobile Web application expert.

DFINITY is building an exciting peer-to-peer WebRTC-based mobile Web app to help improve democracy on the Internet Computer blockchain. The mobile web app connects groups of up to four people in a peer-to-peer WebRTC audio and video call so that they can mutually prove unique personhood.

We are looking for a software engineer or consultant who can help us solve (platform-dependent) reliability issues of our implementation. We are interested in applicants with substantial WebRTC experience for mobile Web apps, experience with different communication patterns (e.g., peer-to-peer, server relay), and substantial problem-solving skills. Having experience in automated testing of this type of applications is a plus. Pay is extremely competitive for the right expertise. For details, please see the full job description.

features

This package is used by WebTorrent and many others.

install

npm install simple-peer

This package works in the browser with browserify. If you do not use a bundler, you can use the simplepeer.min.js standalone script directly in a <script> tag. This exports a SimplePeer constructor on window. Wherever you see Peer in the examples below, substitute that with SimplePeer.

usage

Let's create an html page that lets you manually connect two peers:

<html>
  <body>
    <style>
      #outgoing {
        width: 600px;
        word-wrap: break-word;
        white-space: normal;
      }
    </style>
    <form>
      <textarea id="incoming"></textarea>
      <button type="submit">submit</button>
    </form>
    <pre id="outgoing"></pre>
    <script src="simplepeer.min.js"></script>
    <script>
      const p = new SimplePeer({
        initiator: location.hash === '#1',
        trickle: false
      })

      p.on('error', err => console.log('error', err))

      p.on('signal', data => {
        console.log('SIGNAL', JSON.stringify(data))
        document.querySelector('#outgoing').textContent = JSON.stringify(data)
      })

      document.querySelector('form').addEventListener('submit', ev => {
        ev.preventDefault()
        p.signal(JSON.parse(document.querySelector('#incoming').value))
      })

      p.on('connect', () => {
        console.log('CONNECT')
        p.send('whatever' + Math.random())
      })

      p.on('data', data => {
        console.log('data: ' + data)
      })
    </script>
  </body>
</html>

Visit index.html#1 from one browser (the initiator) and index.html from another browser (the receiver).

An "offer" will be generated by the initiator. Paste this into the receiver's form and hit submit. The receiver generates an "answer". Paste this into the initiator's form and hit submit.

Now you have a direct P2P connection between two browsers!

A simpler example

This example create two peers in the same web page.

In a real-world application, you would never do this. The sender and receiver Peer instances would exist in separate browsers. A "signaling server" (usually implemented with websockets) would be used to exchange signaling data between the two browsers until a peer-to-peer connection is established.

data channels

var Peer = require('simple-peer')

var peer1 = new Peer({ initiator: true })
var peer2 = new Peer()

peer1.on('signal', data => {
  // when peer1 has signaling data, give it to peer2 somehow
  peer2.signal(data)
})

peer2.on('signal', data => {
  // when peer2 has signaling data, give it to peer1 somehow
  peer1.signal(data)
})

peer1.on('connect', () => {
  // wait for 'connect' event before using the data channel
  peer1.send('hey peer2, how is it going?')
})

peer2.on('data', data => {
  // got a data channel message
  console.log('got a message from peer1: ' + data)
})

video/voice

Video/voice is also super simple! In this example, peer1 sends video to peer2.

var Peer = require('simple-peer')

// get video/voice stream
navigator.mediaDevices.getUserMedia({
  video: true,
  audio: true
}).then(gotMedia).catch(() => {})

function gotMedia (stream) {
  var peer1 = new Peer({ initiator: true, stream: stream })
  var peer2 = new Peer()

  peer1.on('signal', data => {
    peer2.signal(data)
  })

  peer2.on('signal', data => {
    peer1.signal(data)
  })

  peer2.on('stream', stream => {
    // got remote video stream, now let's show it in a video tag
    var video = document.querySelector('video')

    if ('srcObject' in video) {
      video.srcObject = stream
    } else {
      video.src = window.URL.createObjectURL(stream) // for older browsers
    }

    video.play()
  })
}

For two-way video, simply pass a stream option into both Peer constructors. Simple!

Please notice that getUserMedia only works in pages loaded via https.

dynamic video/voice

It is also possible to establish a data-only connection at first, and later add a video/voice stream, if desired.

var Peer = require('simple-peer') // create peer without waiting for media

var peer1 = new Peer({ initiator: true }) // you don't need streams here
var peer2 = new Peer()

peer1.on('signal', data => {
  peer2.signal(data)
})

peer2.on('signal', data => {
  peer1.signal(data)
})

peer2.on('stream', stream => {
  // got remote video stream, now let's show it in a video tag
  var video = document.querySelector('video')

  if ('srcObject' in video) {
    video.srcObject = stream
  } else {
    video.src = window.URL.createObjectURL(stream) // for older browsers
  }

  video.play()
})

function addMedia (stream) {
  peer1.addStream(stream) // <- add streams to peer dynamically
}

// then, anytime later...
navigator.mediaDevices.getUserMedia({
  video: true,
  audio: true
}).then(addMedia).catch(() => {})

in node

To use this library in node, pass in opts.wrtc as a parameter (see the constructor options):

var Peer = require('simple-peer')
var wrtc = require('wrtc')

var peer1 = new Peer({ initiator: true, wrtc: wrtc })
var peer2 = new Peer({ wrtc: wrtc })

api

peer = new Peer([opts])

Create a new WebRTC peer connection.

A "data channel" for text/binary communication is always established, because it's cheap and often useful. For video/voice communication, pass the stream option.

If opts is specified, then the default options (shown below) will be overridden.

{
  initiator: false,
  channelConfig: {},
  channelName: '<random string>',
  config: { iceServers: [{ urls: 'stun:stun.l.google.com:19302' }, { urls: 'stun:global.stun.twilio.com:3478?transport=udp' }] },
  offerOptions: {},
  answerOptions: {},
  sdpTransform: function (sdp) { return sdp },
  stream: false,
  streams: [],
  trickle: true,
  allowHalfTrickle: false,
  wrtc: {}, // RTCPeerConnection/RTCSessionDescription/RTCIceCandidate
  objectMode: false
}

The options do the following:

peer.signal(data)

Call this method whenever the remote peer emits a peer.on('signal') event.

The data will encapsulate a webrtc offer, answer, or ice candidate. These messages help the peers to eventually establish a direct connection to each other. The contents of these strings are an implementation detail that can be ignored by the user of this module; simply pass the data from 'signal' events to the remote peer and call peer.signal(data) to get connected.

peer.send(data)

Send text/binary data to the remote peer. data can be any of several types: String, Buffer (see buffer), ArrayBufferView (Uint8Array, etc.), ArrayBuffer, or Blob (in browsers that support it).

Note: If this method is called before the peer.on('connect') event has fired, then an exception will be thrown. Use peer.write(data) (which is inherited from the node.js duplex stream interface) if you want this data to be buffered instead.

peer.addStream(stream)

Add a MediaStream to the connection.

peer.removeStream(stream)

Remove a MediaStream from the connection.

peer.addTrack(track, stream)

Add a MediaStreamTrack to the connection. Must also pass the MediaStream you want to attach it to.

peer.removeTrack(track, stream)

Remove a MediaStreamTrack from the connection. Must also pass the MediaStream that it was attached to.

peer.replaceTrack(oldTrack, newTrack, stream)

Replace a MediaStreamTrack with another track. Must also pass the MediaStream that the old track was attached to.

peer.addTransceiver(kind, init)

Add a RTCRtpTransceiver to the connection. Can be used to add transceivers before adding tracks. Automatically called as neccesary by addTrack.

peer.destroy([err])

Destroy and cleanup this peer connection.

If the optional err parameter is passed, then it will be emitted as an 'error' event on the stream.

Peer.WEBRTC_SUPPORT

Detect native WebRTC support in the javascript environment.

var Peer = require('simple-peer')

if (Peer.WEBRTC_SUPPORT) {
  // webrtc support!
} else {
  // fallback
}

duplex stream

Peer objects are instances of stream.Duplex. They behave very similarly to a net.Socket from the node core net module. The duplex stream reads/writes to the data channel.

var peer = new Peer(opts)
// ... signaling ...
peer.write(new Buffer('hey'))
peer.on('data', function (chunk) {
  console.log('got a chunk', chunk)
})

events

Peer objects are instance of EventEmitter. Take a look at the nodejs events documentation for more information.

Example of removing all registered close-event listeners:

peer.removeAllListeners('close')

peer.on('signal', data => {})

Fired when the peer wants to send signaling data to the remote peer.

It is the responsibility of the application developer (that's you!) to get this data to the other peer. This usually entails using a websocket signaling server. This data is an Object, so remember to call JSON.stringify(data) to serialize it first. Then, simply call peer.signal(data) on the remote peer.

(Be sure to listen to this event immediately to avoid missing it. For initiator: true peers, it fires right away. For initatior: false peers, it fires when the remote offer is received.)

peer.on('connect', () => {})

Fired when the peer connection and data channel are ready to use.

peer.on('data', data => {})

Received a message from the remote peer (via the data channel).

data will be either a String or a Buffer/Uint8Array (see buffer).

peer.on('stream', stream => {})

Received a remote video stream, which can be displayed in a video tag:

peer.on('stream', stream => {
  var video = document.querySelector('video')
  if ('srcObject' in video) {
    video.srcObject = stream
  } else {
    video.src = window.URL.createObjectURL(stream)
  }
  video.play()
})

peer.on('track', (track, stream) => {})

Received a remote audio/video track. Streams may contain multiple tracks.

peer.on('close', () => {})

Called when the peer connection has closed.

peer.on('error', (err) => {})

Fired when a fatal error occurs. Usually, this means bad signaling data was received from the remote peer.

err is an Error object.

error codes

Errors returned by the error event have an err.code property that will indicate the origin of the failure.

Possible error codes:

connecting more than 2 peers?

The simplest way to do that is to create a full-mesh topology. That means that every peer opens a connection to every other peer. To illustrate:

full mesh topology

To broadcast a message, just iterate over all the peers and call peer.send.

So, say you have 3 peers. Then, when a peer wants to send some data it must send it 2 times, once to each of the other peers. So you're going to want to be a bit careful about the size of the data you send.

Full mesh topologies don't scale well when the number of peers is very large. The total number of edges in the network will be full mesh formula where n is the number of peers.

For clarity, here is the code to connect 3 peers together:

Peer 1

// These are peer1's connections to peer2 and peer3
var peer2 = new Peer({ initiator: true })
var peer3 = new Peer({ initiator: true })

peer2.on('signal', data => {
  // send this signaling data to peer2 somehow
})

peer2.on('connect', () => {
  peer2.send('hi peer2, this is peer1')
})

peer2.on('data', data => {
  console.log('got a message from peer2: ' + data)
})

peer3.on('signal', data => {
  // send this signaling data to peer3 somehow
})

peer3.on('connect', () => {
  peer3.send('hi peer3, this is peer1')
})

peer3.on('data', data => {
  console.log('got a message from peer3: ' + data)
})

Peer 2

// These are peer2's connections to peer1 and peer3
var peer1 = new Peer()
var peer3 = new Peer({ initiator: true })

peer1.on('signal', data => {
  // send this signaling data to peer1 somehow
})

peer1.on('connect', () => {
  peer1.send('hi peer1, this is peer2')
})

peer1.on('data', data => {
  console.log('got a message from peer1: ' + data)
})

peer3.on('signal', data => {
  // send this signaling data to peer3 somehow
})

peer3.on('connect', () => {
  peer3.send('hi peer3, this is peer2')
})

peer3.on('data', data => {
  console.log('got a message from peer3: ' + data)
})

Peer 3

// These are peer3's connections to peer1 and peer2
var peer1 = new Peer()
var peer2 = new Peer()

peer1.on('signal', data => {
  // send this signaling data to peer1 somehow
})

peer1.on('connect', () => {
  peer1.send('hi peer1, this is peer3')
})

peer1.on('data', data => {
  console.log('got a message from peer1: ' + data)
})

peer2.on('signal', data => {
  // send this signaling data to peer2 somehow
})

peer2.on('connect', () => {
  peer2.send('hi peer2, this is peer3')
})

peer2.on('data', data => {
  console.log('got a message from peer2: ' + data)
})

memory usage

If you call peer.send(buf), simple-peer is not keeping a reference to buf and sending the buffer at some later point in time. We immediately call channel.send() on the data channel. So it should be fine to mutate the buffer right afterward.

However, beware that peer.write(buf) (a writable stream method) does not have the same contract. It will potentially buffer the data and call channel.send() at a future point in time, so definitely don't assume it's safe to mutate the buffer.

connection does not work on some networks?

If a direct connection fails, in particular, because of NAT traversal and/or firewalls, WebRTC ICE uses an intermediary (relay) TURN server. In other words, ICE will first use STUN with UDP to directly connect peers and, if that fails, will fall back to a TURN relay server.

In order to use a TURN server, you must specify the config option to the Peer constructor. See the API docs above.

js-standard-style

Who is using simple-peer?

license

MIT. Copyright (c) Feross Aboukhadijeh.