Node.js and websockets intro

Node.js and WebSockets A (very) short introduction Andreas Kompanez Montag, 26. April 2010

Node.js JavaScript Framework Server-side Uses V8 Evented and non-blocking CommonJS Uses ECMAScript 5 Montag, 26. April 2010

Node.js Created by Ryan Dahl ~8000 lines of C/C++ and 2000 lines JavaScript http://nodejs.org/ Montag, 26. April 2010

Evented? Old (blocking) school: <?php $content = file_get_contents("/some/huge/file"); doThings($content); // Waiting, synchron otherThing(); Montag, 26. April 2010

Evented? Evented I/O file.read("/some/huge/file", function(data) { // called after data is read doThings(data); }); otherThing(); // execute immediately; Montag, 26. April 2010

Benefits Asynchronous programming Event-loops instead of threads Non-blocking 1 Thread (No context switching etc.) Montag, 26. April 2010

CommonJS Montag, 26. April 2010

CommonJS A collection/library of standards Modules Binary File system and many more! Montag, 26. April 2010

CommonJS Modules There should be a function require There should be a var called exports Montag, 26. April 2010

Module Example // math.js module exports.multiply = function(a, b) { return a * b; } // Some other file, using math.js // var math = require('./math'); var sys = require('sys'); sys.puts(math.multiply(12, 12)); Montag, 26. April 2010

Google V8 JavaScript Engine It’s a VM! Developed by Google The team lead is Lars Bak (Sun’s Java VM & Smalltalk VM) No JIT, compiled to Assembler Montag, 26. April 2010

The 6+ lines http server // httpserver.js // Usage: node httpserver.js var sys = require("sys"), http = require("http"); http.createServer(function(request, response) { var headers = { "Content-Type": "text/plain" }; response.sendHeader(200, headers); response.write("Hello, World!n"); response.close(); }).listen(8000); sys.puts("Running at http://127.0.0.1:8000/"); Montag, 26. April 2010

WebSockets Montag, 26. April 2010

WebSockets A HTML5 standard Allows bidirectional communications Less overhead than HTTP/AJAX (less headers) Cross domain Montag, 26. April 2010

Polling Client Mailman Server Montag, 26. April 2010

Bidirectional Client Telephone Server Montag, 26. April 2010

WS Communication details Handshake GET /test HTTP/1.1 HTTP/1.1 101 Web Socket Protocol Handshake Upgrade: WebSocket Upgrade: WebSocket Connection: Upgrade Connection: Upgrade Origin: http://localhost/test Server: Resin/4.0.2 Host: localhost WebSocket-Location: ws://localhost/websocket Content-Length: 0 WebSocket-Origin: http://localhost/test Content-Length: 0 Date: Fri, 08 May 2009 09:51:31 GMT Messages x00hello, worldxff Montag, 26. April 2010

WebSockets Client- side if (("WebSocket" in window)) { var ws = new WebSocket("ws://localhost:8080/"); ws.onmessage = function(evt) { // Receive }; ws.onopen = function(evt) { // ws.send('Oh hai'); }; ws.onclose = function(evt) { // }; ws.onerror = function(evt) { // }; ws.close(); } Montag, 26. April 2010

Demo! Montag, 26. April 2010

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Node.js and websockets intro

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