This document discusses the potential of WebRTC DataChannels to enable peer-to-peer data transfer between browsers. It outlines how DataChannels allow arbitrary binary data transfer, which could enable new applications like real-time multiplayer games, high-frequency messaging, and decentralized file sharing without servers. However, challenges remain around browser compatibility, binary serialization formats, and issues like NAT traversal that WebRTC does not currently solve. The document argues that within a year most browsers will support DataChannels, fundamentally changing the ability for clients to communicate directly and enabling new networking models for the web.

1. OMG
DATA
CHANNELS
AND HOW TO USE THEM
ERIC ZHANG
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2. BINARY TYPES IN
JAVASCRIPT
Yes binary types exists:
ArrayBuffer
Blob
ArrayBufferView: Uint8Array, etc..
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3. WHY IS THIS COOL
Binary support means we can do
anything we want with data
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4. BINARY TYPES IN
JAVASCRIPT
Do these things with them:
URL.createObjectURL(blob)
XHR2
WebSocket
DataChannel
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5. BACK TO
DATACHANNEL
Video and audio is pretty cool
But I’m excited about DataChannel
because
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6. BACK TO
DATACHANNEL
Arbitrary binary data between
arbitrary people
That is a lot of power
No permissions. No flags.
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7. BUT WAIT THERES
MORE
Based on UDP – essential when
transmission delay matters
Configurable with SCTP, for TCP like
reliability if you want
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8. WHAT I REALIZED
DataChannel fundamentally changes
the web.
Data has always flowed between
server and client.
DataChannel allows client to client
flow
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9. THE POSSIBILITIES
File transfer
Faster
No privacy issues
No bandwidth costs
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10. THE POSSIBILITIES
Multiplayer games
Substantially higher performance
because of lower UDP latency +
binary data
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11. THE POSSIBILITIES
High frequency events and messaging
Higher message rates possible with
UDP based transport
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12. PRIVACY
Imagine a decentralized Facebook
Data actually downloaded from your
browser while you browse the web.
Seamless experience
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13. DATACHANNEL
CHALLENGES
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14. BROWSER
COMPATIBILITY
Google Chrome - March 7th 2013
GOOD
GOOD
GOOD
BAD
No SCTP implementation = No binary, reliable
Not coming until later in 27
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15. BROWSER
COMPATIBILITY
Firefox – March 7th 2013
Nightly 22.0a1 - Several spec issues
being fixed RIGHT NOW
Bug 837919 - WebRTC: RTCPeerConnection constructor: FQDN not yet implemented (only IP-
#s).
Bug 846110 - PeerConnection ondatachannel callback receives channel in Firefox, but
in Chrome an event is passed in
Bug 837035 - Hook up DataChannel SDP to implementation (in particular port and
options)
Aurora 21.01a2 - Flagless support
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16. BROWSER
COMPATIBILITY
Binary, reliable, and FF/Chrome
interop in stable versions at most a
few months away
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17. PROBLEM: JSON
I now have a binary DataChannel
between two browsers.
I want to send some binary data.
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18. PROBLEM: JSON
JSON is an extremely bad choice for
binary data. Base64 uses 37% more
bandwidth and is slow to
encode/decode.
You can never do this in JSON:
JSON.stringify({x: 1, y: binary });
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19. PROBLEM: JSON
Our DataChannel supports binary,
why use string serialization at all?
Binary serialization options:
MsgPack, Thrift, Avro, BSON,
ProtoBufs, BERT, and many more
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20. PROBLEM: JSON
MessagePack: Most JSON like. Very
compact. No schema, not designed
for typed languages like others.
Shitty for Javascript. JS has distinct
string / byte array types unlike many
other dynamic languages.
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21. PROBLEM: JSON
Solution is simple. Add string type to
MessagePack.
They hate this.
https://github.com/msgpack/msgpack/issues/121
https://github.com/msgpack/msgpack/issues/128
Talk to me about this afterwards
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22. PROBLEM: JSON
With a binary serialization format you
can do this:
blob = pack({x: 1, y: binary });
unpack(blob)
-> {x:1, y: binary}
Caveat: JS makes serializing part of UTF8 to binary hard. JSON is
much better.
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23. PROBLEM:
NAT TRAVERSAL
WebRTC takes care of NAT traversal
for you
But not if they are behind symmetric
NATs
~8% of connections according to
Google Talk dev help page
https://code.google.com/p/libjingle/wiki/FAQ
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24. PROBLEM:
NAT TRAVERSAL
You must provide both a TURN server,
a proxy for connections when things
don’t work right.
No bandwidth , latency savings in this
case.
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25. PROBLEM:
NOTIFYING CLIENTS
In order to establish connection,
offer/answer and ICE candidates must
be exchanged.
Solution:
You have to keep a WebSocket or XHR
stream or similar open. Consider
scaling issues.
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26. WEBRTC IS
SUPER
HAPPENING
GUARANTEED
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27. THIS ISNT LIKE THE
IPHONE
Whether you like it or not, almost
everyone is going to have WebRTC
and DataChannels in their browser
within a year.
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28. THIS IS CRAZY
The model of the web can
fundamentally change
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29. THIS IS CRAZY
Someone is going to build the P2P file
transfer app that is ridiculously easy
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30. THIS IS CRAZY
Someone is going to build the
networking library for MMOs in the
browser
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31. THIS IS CRAZY
Someone is going to build the
BitTorrent of the web – just go on the
damn page and start downloading
movies (I mean Ubuntu ISOs). Crazy.
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32. THIS IS CRAZY
Someone is going to build the Node.js
of the browser.
File/network I/O, Sessions, persistent
memory in HTML5 storage, database
drivers, etc.
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33. THIS IS CRAZY
Someone is going to replace Skype,
and fragmented VOIP apps , and
telephones in general with the one
that just works in your browser.
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34. THIS IS CRAZY
Someone is going to build the peer-to-
peer CDN of the future.
http://peerkit.com
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35. THIS IS CRAZY
These aren’t novel ideas.
These are real problems. People have
been talking about them forever.
The technology just hasn’t existed
until today.
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36. THANKS FOR PAYING
ATTENTION
Now go home and code.
Twitter: @reallyez
Github: ericz
I’m currently working on PeerJS and
PeerKit. If you’re interested in this stuff, I’d
love to talk to you.
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