Intro to WebSockets
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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.
Intro to WebSockets
- 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!
- 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