WebSockets Everywhere: the Future Transport Protocol

WebSockets Everywhere: the Future
Transport Protocol for Everything
(Almost)

Dan Shappir
CTO at Ericom Software
@DanShappir
blog: ericomguy.blogspot.com
Six-time BriForum speaker

Remember DCOM?
● Microsoft Distributed COM, circa 1996
● General purpose communication layer for
client / server
● UDP-based, using ports 1024-5000
● COM succeeded; DCOM failed
Can you guess why?

Network Security Realities
● Firewalls/proxies dislike UDP
● Firewalls/proxies often dislike TCP
● Firewalls/proxies like HTTP (80) and HTTPS
(443)
o But dislike most any other port
Stateful Inspection means that just tunneling
through ports 80 and 443 isn’t enough

Make Apps Look Like Websites
Use HTTP / HTTPS as an applicative transport
Example: RD Gateway (tunnels RDP through HTTPS)
● Web Services
● XML and SOAP
● RESTful APIs
● JSON
● AJAX

HTTP Was Designed For Docs Not Apps
● Built on TCP Sockets but ...
● Request / Response architecture
o Only client can send Requests
o Server can only Respond to Requests
o Can’t send another Request before Response
● Header on every Request / Response
o Up to 8KB each

Various Workarounds
COMET
● Persistent connections (HTTP 1.1)
● Polling
● Long Polling
● Chunked Response
● Multiple channels
● Pipelining
● Two-way HTTP

Problems With Workarounds
● Hacks: error prone
● Complicated
● Compatibility issues
● Headers overhead
o Especially if contains cookies

Need a Better Solution
Flexibility of Sockets + reach of Web (HTTP)

WebSockets - Sockets for the Web
● Part of HTML5: W3C API and IETF Protocol
● Full-duplex, bidirectional communication
● Unsecured (TCP) and secured (SSL) modes
● Traverses firewalls, proxies and routers
● Text (UTF-8) and binary data
● Ping/Pong messages for keep-alive
● Share ports 80 and 443 with HTTP/HTTPS

WebSocket Connection Process
1. Client opens new TCP connection to Server
2. Optional SSL (TLS) handshake
3. Client sends HTTP GET Request
4. Server sends HTTP Response
5. Magic: Client & Server communicate using
WebSocket packets

WebSocket Request
GET /blaze HTTP/1.1
Host: an.ericom.com
Connection: Upgrade
Upgrade: websocket
Sec-WebSocket-Key: oY+dTudispTU+nqsq5XXVw==
Sec-WebSocket-Version: 13
Sec-WebSocket-Protocol: ericom|accessnow.3
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits,
x-webkit-deflate-frame
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36
Origin: http://127.0.0.1

WebSocket Response
HTTP/1.1 101 Switching Protocols
Connection: Upgrade
Upgrade: websocket
Sec-WebSocket-Accept:kgTM0bjagqwcNTJaj/VZZZZCJ5Q=
Sec-WebSocket-Protocol:ericom|accessnow.3

WebSocket Response
HTTP/1.1 101 Switching Protocols
Connection: Upgrade
Upgrade: websocket
Sec-WebSocket-Accept: kgTM0bjagqwcNTJaj/VZZZZCJ5Q=
Sec-WebSocket-Protocol: ericom|accessnow.3

Packet Oriented Protocol
● After handshake, protocol is sequence of
packets
● Packets comprised of header + payload
● Several packet types
● Peers receive full data packets payload
o Not partial packets / bytes
o Not control packets

WebSocket Packet
Minimally framed: small header + payload
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
F
I
N
R
S
V
1
R
S
V
2
R
S
V
3
opcode(4)
M
A
S
K
payload
len(7)
extended payload len(16/64)
extended payload len continued(16/64)
masking key(0/32)
masking key continued payload ...

Packet Opcodes (Types)
0 - continuation frame
1 - text frame (UTF-8)
2 - binary frame
3-7 - reserved (data)
8 - connection close
9 - ping
10 - pong
11-15 - reserved (control)

Simple JavaScript Example
var ws = new WebSocket("ws://...");
ws.onopen = function () {
ws.send("hello");
};
ws.onmessage = function (event) {
console.log(event.data);
};

Growing Support
● Browsers
o Everybody!
● Webservers
o Most everybody!
● Firewalls
o Often just works
● SSL VPN
o Juniper, Cisco, CheckPoint, …

Benefits of SSL VPNs over VPNs
For Web protocols: HTTP and WebSockets
● No client-side installation
● No client-side configuration
● Any client device

WebSockets For Native Apps
● .NET (4.5) WCF support
● Java EE (JSR-356)
● C/C++ - several Open Source implementations
● PHP - Rachet
● Node.js - multiple libraries

WebSockets Extensions
Utilizing Sec-WebSocket-Extensions in
Request/Response Headers:
1. Compression (deflate)
2. Multiplexing

What If It Doesn’t Connect?
● Use standard ports: 80, 443
o Or standard alternate ports: 8080, 8443, 8008
● Use SSL, with proper certificates
● Upgrade SSL VPN, Firewall, …
● Disable anti-virus
o Or exception, or disable packet inspection
● Fallback to HTTP / HTTPS

Future Protocol For Everything?
No, primarily when UDP is required
● Streaming Video or Video Conferencing
● Remote access over bad connections
(“Framehawk” scenario)

The Future, Future Protocol
● For UDP: WebRTC with data-channels
o Use WebSockets as fallback
● For TCP: WebSockets
o Use HTTP / HTTPS as fallback
● HTTP / HTTPS for RESTful APIs

Summary
WebSockets couple the performance and
flexibility of TCP with the reach of HTTP
Prediction: WebSockets will replace simple
TCP as preferred underlying protocol
Existing protocols wrapped in WebSockets

WebSockets Everywhere: the Future Transport Protocol

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