WebSockets allow for bidirectional communication between a client and server over a single TCP connection. They provide lower latency and overhead than traditional HTTP requests which require a new connection for each request. The talk demonstrated how to use WebSockets with JavaScript on the client and event-driven servers like Node.js on the server. While browser support is still limited and the specification is in flux, WebSockets offer a way to build real-time applications without hacks like long-polling that HTTP requires.

1. WebSocketsA quick tour and demoGaurav OberoiDec 18, 2010 - Chennai Geeks

2. Who am I?Entrepreneur: started and sold 2 companiesBillMonk (consumer)Precision Polling (SaaS)Programmer, Product Manager:Amazon, Obopay, Xmarks, SurveyMonkeyGeneral geekery:Seattle Tech Startups founder (~2200 member list)TechStars mentor, advisor to startups

3. What is this talk about?What are WebSockets?Why do we need them?How do we use them?What limitations do they have?

4. DisclaimerHaven’t deployed production code using WebSockets.Not an expert!

5. What are WebSockets?+= ?

6. According to the textbook:WebSocket is a technology for providing bi-directional full duplex communication channels over a single TCP socket.Ahem…

7. Put simply, WebSockets:Are a new feature in HTML5 (draft) that let you stream data to and from web browsers.

8. For comparison:Here’s good ol’ HTTP request and response:GET /index.html200 OK (...)With sockets, send data back and forth anytime:

9. More juicy detailsNew protocol (ws:// and wss://)W3C and IETF standardCurrently a draft, more on this laterUses ports 80 and 443443 recommended for proxy traversalStarts as HTTP, then switches to WSSupports >1 connections over 1 TCP socket

10. More juicy details: the handshakeClient sends:Server responds:

11. Yawn…… so why do we need WebSockets?

12. 2 good reasons

13. First: desire for real-timeWant low latency 2-way communication for:Gaming (pong)Collaboration (live wikis)Dashboards (financial apps)Tracking (watch user actions)Presence (chat with customer support)More!

14. Second: HTTP doesn’t deliverPeople hack around this (see “Comet”)Polling, long-polling, stream via hidden iframeBUT these are slow, complex, and bulkyOr rely on plugins:Flash, Silverlight, Java appletsBUT these don’t work everywhere (phones)

15. Damn, this is hairy:Source: http://www.slideshare.net/ismasan/websockets-and-ruby-eventmachine

16. Vs. HTTP hacks, Websockets provide:Lower latency: no new TCP connections for each HTTP requestLower overhead: for each message sent(2 bytes vs. lines of HTTP header junk)Less traffic: since clients don’t need to poll, messages only sent when we have data

17. How do we use WebSockets?

18. What you’ll need:WebSockets compliant browserWebKit: Chrome, Safari (works on iOS)Client Javascript APIServer-side API

19. Client API in JavascriptInitialize:varws = new WebSocket(“ws://example.com”)Send data:send(data)Event-handlers:onopenonmessageoncloseonerror

20. Server-side APIThreaded servers can be used but not recommended:1 thread/process per socket  memory hog!Evented-servers are ideal:1 process handles all requestsWaits for I/O before processing requests (reactor pattern)Suggested servers:Ruby: Event Machine + em-websocketJavascript: Node.js + WebSocket modulePython: Twisted + txWebSocket

21. DEMO TIME!

22. What limitations do WebSockets have?

23. First, the big onesNot all browsers support themNo support in Firefox 4, IE9, OperaSo you need to fallback to something that worksSee Socket.IO: client and server library for graceful fallbackDraft spec in jeopardy after Dec 8 security announcement by MozillaSecurity vulnerabilities with transparent proxiesNot caused by WebSockets, but they expose issueMy guess: we’ll get by this with some spec changes

24. And the other thingsWebSockets need maintenance and care:Re-open connif network hiccup or timeoutBack off if server is down, don’t keep tryingKeep alive if your connection times outBuffer and re-send msgs in the above casesMy guess: libraries will fill in these gaps

25. In ConclusionWebSockets == “TCP for the Web”Easy JS library, evented-servers on the backNot prod ready, but soon (fingers crossed)Check out some demos:http://websockets.org/demos.html

26. twitter.com/goberoi