The State of WebRTC

WEBRTC
T H E S T A T E O F
@ROBHAWKES
Hi, I’m Rob Hawkes and I’m here today to talk about the state of WebRTC.

ROB HAWKES
WHO IS
A little about me…
- Digital Tinkerer (I play with new technologies and see how far I can push them)
- Former Technical Evangelist at Mozilla (worked on HTML5 games, Firefox OS, and Web tech in general)
- Author of multiple books, such as Foundation HTML5 Canvas
- Currently taking time out to work on personal projects, such as…

VIZICITIES.COM
ViziCities, an experimental project that uses WebGL to bring real-world cities to life in the browser… in 3D!
http://vizicities.com

@ROBHAWKES
WHAT IS WEBRTC?
What is WebRTC?
Peer-to-peer communication technology for the browser.

@ROBHAWKES
WEBRTC IS A FREE, OPEN
PROJECT THAT ENABLES WEB
BROWSERS WITH REAL-TIME
C O M M U N I C A T I O N S ( R T C )
C A P A B I L I T I E S V I A S I M P L E
JAVASCRIPT APIS.
WEBRTC.ORG
“WebRTC is a free, open project that enables web browsers with Real-Time Communications (RTC) capabilities via
simple Javascript APIs.”
http://www.webrtc.org

@ROBHAWKES
AT A BASIC LEVEL, WEBRTC IS
LIKE SKYPE RUNNING IN THE
BROWSER. SORT OF…
ROB HAWKES
At a basic level, WebRTC is like Skype running in the browser.
However, this is barely scratching the surface of what it can really do.

@ROBHAWKES
WebRTC is a W3C speciﬁcation, supported by Google, Mozilla, and Opera, amongst others.
It’s currently in the editorial process and is not yet a full recommendation.
The spec is a fantastic resource for in-depth technical information about WebRTC and how it should be implemented
as per the browser. It’s a good read if you want to get right into the API structure.
http://dev.w3.org/2011/webrtc/editor/webrtc.html

@ROBHAWKES
The official WebRTC site is also a fantastic resource for a slightly more human-readable overview of the technology
and the underlying architecture supporting it.
The FAQ is also a good place to start when you have questions.
http://www.webrtc.org/

@ROBHAWKES
WEBRTC
VS
WEBSOCKETS
Now we already have real-time communication technologies such as WebSockets, so why use WebRTC?
At the the most basic level, WebSockets and WebRTC achieve different goals.
WebSockets is purely about providing a reliable real-time data connection in JavaScript.
On the other hand, WebRTC is about providing a network infrastructure for real-time media communication.

@ROBHAWKES
WEBSOCKETS
Communication methods such as WebSockets require a server to act as a middleman, passing messages back and
forth between users.

@ROBHAWKES
WEBSOCKETS
The problem with a middleman approach is that you have to wait for your message to reach the server, be passed
onto and reach the recipient, have a response sent back to the server, which in turn is then sent back to you.
If both users had a latency to the server of 20ms, which is conservative, a round trip between the two users would
take 80ms. That’s nearly a tenth of a second, just ferrying messages back and forth.

@ROBHAWKES
WEBRTC
On the other hand, WebRTC is a peer-to-peer connection directly between 2 users. No middleman.

@ROBHAWKES
WEBRTC
This means you can send messages directly to the other user without hopping via a server.
If the latency between the users was 20ms then a round-trip would take just 40ms, half the time it would take with
something like WebSockets.

@ROBHAWKES
UDP
VS
TCP
Another big draw to WebRTC is that it primarily uses UDP, a method for sending data across a network in an
unreliable fashion.
In comparison, technologies such as HTTP use TCP which is a reliable method of sending data.
Without going into too much detail, UDP is a lot faster than TCP because it doesn’t worry about order or error
correction. Because of this you wouldn’t want to use it to send important data that needs to be received in order and
whole.
Instead, UDP is commonly used in situations where you only care about the very latest piece of data and have no
need to wait for data sent in the past to be received correctly. VoIP and multiplayer games are perfect examples of
this.
WebRTC is the ﬁrst time UDP has been available in the browser without plugins and because of this a lot of
developers are excited to get their hands on it. I know I am!
http://www.skullbox.net/tcpudp.php
http://gafferongames.com/networking-for-game-programmers/udp-vs-tcp/

@ROBHAWKES
WEBRTC USE CASES
The ability to connect peer-to-peer with another user certainly sounds cool, but what exactly is it useful for?

@ROBHAWKES
VIDEO AND AUDIO CALLS
The most common use-case is video and audio calls, a la. Skype.
This seems to be the approach most people are taking with WebRTC, which is fair considering that’s what it has been
marketed as.
But WebRTC is more than that…

@ROBHAWKES
SCREEN SHARING
Screensharing is another approach, similar to the idea of sharing video.

@ROBHAWKES
COLLABORATIVE ACTIVITIES
There are also collaborative activities like writing or coding, this is another area which is gaining a lot of interest.

@ROBHAWKES
MULTIPLAYER GAMES
Multiplayer games are an area that will beneﬁt hugely from WebRTC.
This is mainly because of UDP and the ability to have unreliable network data connections, an approach used by the
vast majority of multiplayer games outside of the Web.
We also shouldn’t forget that the peer-to-peer nature of WebRTC will also allow for a new breed of Web games that
don’t need servers to be played multiplayer. That will be very interesting to see progress.

@ROBHAWKES
P2P FILE SHARING
A slightly more interesting use of the technology is peer-to-peer ﬁle sharing.
The ability to quickly send a ﬁle directly to a friend without leaving the browser is certainly an appealing one.
Also, imagine the possibility for something like BitTorrent in the browser!

@ROBHAWKES
P2P CDN
Something I’d never considered before is the idea of using WebRTC to create a peer-to-peer CDN amongst your
website visitors.
The idea of share the serving of assets amongst a network of peer-to-peer connections is very intriguing.

@ROBHAWKES
REMOTE CONTROL
Something that ﬂips the common approach of WebRTC is the idea of remote control of devices from other devices.
In this case, instead of connecting to another browser controlled by another person you are connecting two devices
owned by the same person.
This way you can use one device to control the other without having to worry about a server or Internet connection.
Theoretically this could work over the local network.
One approach where this would be useful is for using mobile phones to act as a gamepad for games playing on a
desktop or TV.

@ROBHAWKES
WEBRTC APIS
There are 3 main APIs involved in WebRTC.
Let’s quickly take a look at each of them.

@ROBHAWKES
MEDIASTREAM
MediaStream API, commonly referred to as getUserMedia.
This API gives you access to media data streams from devices such as webcams and microphones.
http://dev.w3.org/2011/webrtc/editor/getusermedia.html

@ROBHAWKES
GETUSERMEDIA
IS NOT
“WEBRTC SUPPORT”
getUserMedia is not WebRTC.

@ROBHAWKES
PEERCONNECTION
PeerConnection API.
This API lets you make peer-to-peer connections and attach media streams like video and audio.
http://dev.w3.org/2011/webrtc/editor/webrtc.html#peer-to-peer-connections

@ROBHAWKES
DATACHANNEL
DataChannel API.
This API lets you send and receive arbitrary data across a peer-to-peer connection.
http://dev.w3.org/2011/webrtc/editor/webrtc.html#peer-to-peer-data-api

@ROBHAWKES
DESKTOP
SUPPORT
We’ve seen what WebRTC offers, but what is the real-world support like?
It’s still a very new technology but things are looking good, at least on desktop.

@ROBHAWKES
Firefox supports WebRTC by default in version 22, which is currently going through the testing stages in the Nightly
and Aurora versions.
If all goes well, functional WebRTC support will land in the public release of Firefox by the end of June.
https://hacks.mozilla.org/2013/04/webrtc-update-our-ﬁrst-implementation-will-be-in-release-soon-welcome-
to-the-party-but-please-watch-your-head/

@ROBHAWKES
The current public release of Chrome has support for basic audio and video WebRTC calls enabled by default.
DataChannel is supported in Chrome beta and is currently behind a ﬂag.
http://www.html5rocks.com/en/tutorials/webrtc/basics/
http://updates.html5rocks.com/2013/02/WebRTC-data-channels-API-changes-and-Chrome-talks-to-Firefox

@ROBHAWKES
Opera only supports the ability to get video and audio via getUserMedia.
This is not really WebRTC support.

@ROBHAWKES
IE has no WebRTC support natively but support can be added if you use Chrome Frame.
Gotta love Chrome Frame!
http://www.google.com/chromeframe

@ROBHAWKES
MOBILE
SUPPORT
While desktop support is pretty good, considering, mobile support isn’t so good.

@ROBHAWKES
Firefox on Android has WebRTC support behind a config flag.
It’s very early days and your mileage may vary while using it as the mobile implementation is changing quite rapidly.
Mozilla plan to firm up their mobile WebRTC support in the coming months.
http://www.morbo.org/2013/04/webrtc-support-on-android.html

@ROBHAWKES
Chrome on Android also has WebRTC support behind a conﬁg ﬂag.
It seems to be quite reliable and you can certainly make calls between Chrome mobile and a desktop browser. Very
cool!
https://groups.google.com/d/msg/discuss-webrtc/uFOMhd-AG0A/81p3dE_5peYJ

@ROBHAWKES
Opera Mobile only has support for getUserMedia.
Again, this is not really WebRTC support.

@ROBHAWKES
INTEROPERABILITY
Browser support for the APIs is all well and good, but what is the interoperability like?
It’s not very useful to have WebRTC support if you can’t make a call between different browsers and platforms.
Up until recently the situation wasn’t very promising.
http://www.webrtc.org/interop

However, earlier this year it was announced that a WebRTC connection can be made between public builds of Firefox
and Chrome.
This was pretty big news and was co-announced on both the Chrome dev blog and the Mozilla Hacks blog. It was one
of the rare occurrences where the browser wars were put aside and true cooperation was embraced.
http://blog.chromium.org/2013/02/hello-ﬁrefox-this-is-chrome-calling.html
https://hacks.mozilla.org/2013/02/hello-chrome-its-ﬁrefox-calling/
https://apprtc.appspot.com/

@ROBHAWKES
WEBRTC DEMO
If all goes well, I’m going to show you a quick demo of WebRTC.
http://freshtilledsoil.com/the-future-of-web/webrtc-video/
https://apprtc.appspot.com

@ROBHAWKES
USING WEBRTC
Let’s take a look at how to actually use WebRTC.

@ROBHAWKES
MEDIASTREAM
The most basic API to look at ﬁrst is the MediaStream API, speciﬁcally the getUserMedia method.

@ROBHAWKES
var constraints = {video: true};
function successCallback(localMediaStream) {
var video = document.querySelector("video");
video.src = window.URL.createObjectURL(localMediaStream);
video.play();
}
function errorCallback(error){
console.log("getUserMedia error: ", error);
}
getUserMedia(constraints, successCallback, errorCallback);
HTML5ROCKS.COMGETUSERMEDIA DEMO
In this example we have an implementation for accessing the webcam.
It’s pretty basic but it gets the job done. The only other thing you need is a HTML video element to attach the
webcam stream to.
It’s worth pointing out that, although you can’t see it, we’re making use of a simple polyﬁll to remove the (very few)
browser inconsistencies in the API calls.
You also need to run this through a domain, not the local ﬁlesystem, otherwise security restrictions will prevent you
from accessing the media devices.
http://www.simpl.info/getusermedia/
https://code.google.com/p/webrtc-samples/source/browse/trunk/apprtc/js/adapter.js

@ROBHAWKES
PEERCONNECTION
Things get a little more complicated when we look at the PeerConnection API, but once you understand the process
it’s not so bad.
We’ll ﬁrst look at an example that makes a local PeerConnection call within a single browser page.
It’s a good way to look at the code before adding in the extra functionality to make remote calls.

@ROBHAWKES
function start() {
getUserMedia({audio:true, video:true}, gotStream, function() {});
}
function gotStream(stream){
vid1.src = window.URL.createObjectURL(stream);
localstream = stream;
}
...
HTML5ROCKS.COMPEERCONNECTION DEMO (1/4)
In this example we’re again making use of the polyfill to avoid the browser prefix dance. We’re also missing the
HTML as it’s most important to understand the JavaScript.
1. The first step is to call getUserMedia
2. Next, we connect the local stream to a HTML video element to you can see yourself
3. Next, we store a reference to the local stream so we can access it later on
http://www.simpl.info/rtcpeerconnection/
https://code.google.com/p/webrtc-samples/source/browse/trunk/apprtc/js/adapter.js

@ROBHAWKES
...
function call() {
var servers = null;
window.pc1 = new RTCPeerConnection(servers);
pc1.onicecandidate = iceCallback1;
window.pc2 = new RTCPeerConnection(servers);
pc2.onicecandidate = iceCallback2;
pc2.onaddstream = gotRemoteStream;
pc1.addStream(localstream);
pc1.createOffer(gotDescription1);
}
...
At this point we haven’t achieved anything more then the previous getUserMedia example.
Once the webcam and audio is set up we can begin the process of making a PeerConnection.
1. Firstly, we call the RTCPeerConnection method and pass it an empty variable

- This variable can be used to deﬁne TURN and STUN servers, which can help when routing through ﬁrewalls
2. The next step is to set up an event handler for onicecandidate

- This is used to work out which methods work best for making a connection
3. Next, we call RTCPeerConnection again and use this as our ‘remote’ connection
4. We set up the onicecandidate handler for the remote connection
5. And also set up the onaddstream handler for the remote connection

- This lets you know when a remote stream has been received by PeerConnection
6. Now we add the local media stream to the local PeerConnection
7. Finally, we call the createOffer method of PeerConnection and pass a handler to deal with the returned session
description.

- We’ll look at the handler in more detail in a moment

@ROBHAWKES
v=0
o=- 5948426442422644553 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE audio video
a=msid-semantic: WMS qcBqgcQpLthJWqiwDV4Hbujhpj0rTn5vvUZR
m=audio 1 RTP/SAVPF 111 103 104 0 8 107 106 105 13 126
...
a=ssrc:2770545510 label:qcBqgcQpLthJWqiwDV4Hbujhpj0rTn5vvUZRv0
SESSION DESCRIPTION EXAMPLE
The session description we get returned by createOffer is a method of describing the streaming media connection
that we want to make between the two peers.
This is just an example session description; what you see will vary depending on what you’re trying to do and your
network situation.
http://www.html5rocks.com/en/tutorials/webrtc/basics/#toc-signaling
http://en.wikipedia.org/wiki/Session_Description_Protocol

@ROBHAWKES
...
function iceCallback1(event){
if (event.candidate) {
pc2.addIceCandidate(new RTCIceCandidate(event.candidate));
}
}
function iceCallback2(event){
if (event.candidate) {
pc1.addIceCandidate(new RTCIceCandidate(event.candidate));
}
}
...
Moving on; this is what the onicecandidate handlers look like, for both the local (top) and remote (bottom)
connections.
What’s happening here is that the returned connection methods (candidates) are added to the opposite connection so
they both know the best way to connect to the other.
However, we’re still not ready to make the connection.

@ROBHAWKES
...
function gotDescription1(desc){
pc1.setLocalDescription(desc);
pc2.setRemoteDescription(desc);
pc2.createAnswer(gotDescription2);
}
function gotDescription2(desc){
pc2.setLocalDescription(desc);
pc1.setRemoteDescription(desc);
}
function gotRemoteStream(e){
vid2.src = window.URL.createObjectURL(e.stream);
}
The last chunk of code allows us to successfully hook up the PeerConnection and tidy up the loose ends.
1. The ﬁrst thing we do is set up the gotDescription1 handler, which is called by the createOffer method from earlier

- This returns the session description for the local connection
2. We then call the setLocalDescription method on the local PeerConnection
3. We then call the setRemoteDescriotion method on the ‘remote’ PeerConnection

- At this point we’re nearly ready to make the connection, we just need to respond to the offer
4. The next step is to call createAnswer on the ‘remote’ PeerConnection and pass a handler for the returned session
description.
5. From here we jump into the gotDescription2 handler which deals with the session description for the ‘remote’
PeerConnection created by createAnswer

- Now it’s just a case of tying up the loose ends
6. We call setLocalDescription on the ‘remote’ PeerConnection and pass it the session description
7. We then call setRemoteDescription on the local PeerConnection and pass it the same session description

- At this point you’ve successfully connected the two peers, but there is one last step…
8. The last thing to do is to set up the gotRemoteStream handler

- This is called when a media stream is added by a remote peer. Eg, when the connection starts.

- All this does is set the stream, in this case a video, to another HTML video element
And you’re done!

@ROBHAWKES
SIGNALLING
The problem with the previous demo is that it only runs within a single browser page.
Most of you who want to use WebRTC will want to make connections between remote browsers.
A full code example of a remote WebRTC demo is beyond the scope of this talk, though I’ve linked to a great
example in the slides.
Instead, what we can do is brieﬂy take a look at the concept of signalling… the discovery and connection of remote
peers.
http://www.webrtc.org/demo
http://www.html5rocks.com/en/tutorials/webrtc/basics/#toc-signaling

@ROBHAWKES
LOCAL PEERCONNECTION
With the local PeerConnection example the act of peer discovery was not needed as the two peers were running from
the same page and as such knew about each other already.

@ROBHAWKES
DISCOVER PEERS VIA SERVER
#ROOM1 #ROOM1
With a full remote PeerConnection, the ﬁrst step is to use a server to discover other peers (users) wanting to make a
WebRTC connection. Ie. We use the server to work out which computers want to connect with each other as we can’t
do that locally.
Common techniques include the use of a room name or a unique identiﬁer that two peers can both use so the server
knows who to pair.
Once peers are paired a handshake is performed so that each peer knows just enough information to connect to the
other one. This is done by sharing ICE information and the session description.
You’ve already done this with the local demo but it becomes a little more complicated when you do it remotely.
Common approaches for this handshake use AJAX or WebSockets to send the ICE candidates and session descriptions
between peers via the server.
To be clear the server is purely acting as a messaging proxy.
And this is the only step that requires a server.
http://blog.gingertech.net/2012/06/04/video-conferencing-in-html5-webrtc-via-web-sockets/
http://www.html5rocks.com/en/tutorials/webrtc/basics/#toc-signaling-with-channel
https://sites.google.com/site/muazkh/webrtc-order-the-code

@ROBHAWKES
DIRECTLY CONNECT PEERS
Once the session description handshake has been made the two peers will be connected directly.
At this point the server is no longer needed and you have a WebRTC connection up and running.
It sounds quite simple in theory, and it kind of is thanks to the API introduced with WebRTC. The underlying
technology and networking to make this happen is much, much more complicated.

@ROBHAWKES
DATACHANNEL
At this point you may have a PeerConnection set up that is streaming webcam and microphone input between two
browsers.
If you want to then send arbitrary data over the PeerConnection you’ll need to set up a DataChannel.
Let’s look at that next.

@ROBHAWKES
...
window.dc1 = pc1.createDataChannel("dataChannel1", {reliable: false});
...
pc2.ondatachannel = function(event) {
window.dc2 = event.channel;
dc2.onmessage = handleMessage;
};
var handleMessage = function(event) {
console.log("DataChannel message received from pc1: n " + event.data);
}
...
dc1.send("Hello, world!");
DATACHANNEL DEMO
We’ll keep this one brief as it mostly relies on an existing PeerConnection, which you now know how to set up.
In this example we make a call to the createDataChannel method on the local PeerConnection, passing it a label and
some option.
We’re passing the reliable: false property in the options to use unreliable UDP for the DataChannel.
We then set up a handler on the remote PeerConnection to listen for a DataChannel connection.
When the DataChannel is received we store a reference to it and set up a handler to listen for incoming messages.
From there, we can then call the send method on the local DataChannel to send messages to the remote peer.
The DataChannel API is feels very similar to WebSockets.

@ROBHAWKES
WEBRTC IN USE
Now that we’ve seen how WebRTC works, let’s take a look at some of the projects that are using it today.

@ROBHAWKES
TowTruck by Mozilla.
Collaborative browsing, editing, chat, and voice.
Potential demo…
https://towtruck.mozillalabs.com

@ROBHAWKES
Conversat.io
Small video chat rooms.
http://conversat.io/

@ROBHAWKES
PeerJS
Awesome cross-browser DataChannel framework.
They also offer developers free signalling servers for your PeerJS apps, at least up to 50 concurrent connections.
http://peerjs.com/

@ROBHAWKES
Twelephone
Twitter-powered video and text chat.
http://twelephone.com/

@ROBHAWKES
Twilio
Increasingly-popular service that allows you to make and receive real-world phone calls programatically, including
from a browser with WebRTC.
http://www.twilio.com/

@ROBHAWKES
PeerCDN
Offloading the serving of website assets to a peer-to-peer network of connected visitors.
https://peercdn.com/

@ROBHAWKES
Peerkit
Another approach at a peer-to-peer CDN.
Potential demo…
http://peerkit.com/

@ROBHAWKES
BananaBread
Peer-to-peer multiplayer in a 3D WebGL game.
https://hacks.mozilla.org/2013/03/webrtc-data-channels-for-great-multiplayer/

@ROBHAWKES
Experimental sharing of browser tabs in Chrome.
http://updates.html5rocks.com/2012/12/Screensharing-with-WebRTC

@ROBHAWKES
Phono
A jQuery plugin for making phone calls from the browser.
http://phono.com/webrtc

@ROBHAWKES
Att.js
Effectively powered by Phono, with a few extra bits and pieces.
https://att.io/

@ROBHAWKES
OpenTok
Another platform for creating audio and video calls within the browser using WebRTC.
http://www.tokbox.com/

@ROBHAWKES
File Hangout
Experiment with DataChannels for sharing ﬁles amongst multiple peers.
https://webrtc-experiment.appspot.com/ﬁle-hangout/

@ROBHAWKES
Sqwiggle
Collaborative dashboard for remote working, allowing you to see each other and share resources throughout the day.
https://www.sqwiggle.com/

@ROBHAWKES
Ericsson Labs 3D WebRTC demo
Using output from a depth sensor synchronised with a peer-to-peer video call.
https://labs.ericsson.com/blog/3d-webrtc-3d-video-communication-in-a-browser

@ROBHAWKES
Codassium
Collaborative code editor, marketed towards programming interviews.
http://codassium.com/

@ROBHAWKES
Grimewire ‘OS’
A crazy project aimed at creating a browser OS that uses WebRTC. I’m not even sure how yet, but it certainly sounds
cool!
http://blog.grimwire.com/#2013-04-04-grimwire.md

@ROBHAWKES
G O F O R T H
AND WEBRTC!
I hope that I’ve managed to pique your interest in WebRTC enough to start experimenting with it.
There is so much that the technology can do that people just aren’t exploring yet, particularly around to use of
mobile devices.
I’d love to see what you make with it so make sure to ping me on Twitter if you do have a play.

Tweetmap.it
Real-time visualisation of tweets
ViziCities.com
3D visualisation of real-world cities
Slides
slideshare.net/robhawkes
Rawkes.com
Personal website and blog
RECENT PROJECTS MORE COOL STUFF
@robhawkesRob Hawkes
Get in touch with me on Twitter: @robhawkes
Follow my blog (Rawkes) to keep up to date with stuff that I’m working on: http://rawkes.com
ViziCities http://vizicities.com
Tweetmap http://tweetmap.it
These slides are online at http://slideshare.net/robhawkes

The State of WebRTC

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The State of WebRTC