README

simple-peer-light

This is a light-weight, browser-friendly fork of feross/simple-peer:

Zero external dependencies
Bundle size reduced from 28 kB to 5 kB (minified, gzipped)
Can be directly imported in a <script type="module"> without bundling

Caveats compared to feross/simple-peer

No stream API. The Peer class does not inherit from Duplex. Instead, it has only the essential EventEmitter methods .on(), .off(), .once() and .emit().
Browser only. Because index.js uses an ESM export instead of CJS, it does not work in node.
No tests. Browser tests can't be run because they rely on CJS. However, the tests were updated to reflect the API changes and they all pass if a CJS export is used in index.js.

The documentation below is updated to reflect these changes.

Regarding ongoing development in simple-peer, the strategy for this repo is to keep merging in upstream changes while maintaining the initial diff. We will update the npm package accordingly and our versioning will track the version of simple-peer 1:1, to make it obvious at what point of the release history we are.

features

concise, node.js style API for WebRTC
supports video/voice streams
supports data channel
- text and binary data
supports advanced options like:
- enable/disable trickle ICE candidates
- manually set config options
- transceivers and renegotiation
install
examples
api
error codes
connecting more than 2 peers?
memory usage
connection does not work on some networks?
license

install

npm install simple-peer-light

This package works in the browser without modification. The simplepeer.min.js script is just a minified version for usage without a build pipeline.

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 type="module">
      import Peer from './simplepeer.min.js';
      const p = new Peer({
        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

import Peer from 'simple-peer-light';

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.

import Peer from 'simple-peer-light';

// 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.

import Peer from 'simple-peer-light'; // 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(() => {});

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
}

The options do the following:

initiator - set to true if this is the initiating peer
channelConfig - custom webrtc data channel configuration (used by createDataChannel)
channelName - custom webrtc data channel name
config - custom webrtc configuration (used by RTCPeerConnection constructor)
offerOptions - custom offer options (used by createOffer method)
answerOptions - custom answer options (used by createAnswer method)
sdpTransform - function to transform the generated SDP signaling data (for advanced users)
stream - if video/voice is desired, pass stream returned from getUserMedia
streams - an array of MediaStreams returned from getUserMedia
trickle - set to false to disable trickle ICE and get a single 'signal' event (slower)
wrtc - custom webrtc implementation, mainly useful in node to specify in the wrtc package. Contains an object with the properties:

`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, 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.

`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.

import Peer from 'simple-peer-light';

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

`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 Uint8Array.

`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:

ERR_WEBRTC_SUPPORT
ERR_CREATE_OFFER
ERR_CREATE_ANSWER
ERR_SET_LOCAL_DESCRIPTION
ERR_SET_REMOTE_DESCRIPTION
ERR_ADD_ICE_CANDIDATE
ERR_ICE_CONNECTION_FAILURE
ERR_SIGNALING
ERR_DATA_CHANNEL
ERR_CONNECTION_FAILURE

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-light 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.

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.

Usage no npm install needed!

README

simple-peer-light

features

install

usage

A simpler example

data channels

video/voice

dynamic video/voice

api

peer = new Peer([opts])

peer.signal(data)

peer.send(data)

peer.addStream(stream)

peer.removeStream(stream)

peer.addTrack(track, stream)

peer.removeTrack(track, stream)

peer.replaceTrack(oldTrack, newTrack, stream)

peer.addTransceiver(kind, init)

peer.destroy([err])

Peer.WEBRTC_SUPPORT

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

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

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

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

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

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

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