1.
Node.js and
WebSockets
A (very) short introduction
Andreas Kompanez
Montag, 26. April 2010

2.
Node.js
JavaScript Framework
Server-side
Uses V8
Evented and non-blocking
CommonJS
Uses ECMAScript 5
Montag, 26. April 2010

3.
Node.js
Created by Ryan Dahl
~8000 lines of C/C++ and 2000 lines
JavaScript
http://nodejs.org/
Montag, 26. April 2010

4.
Evented?
Old (blocking) school:
<?php
$content = file_get_contents("/some/huge/file");
doThings($content); // Waiting, synchron
otherThing();
Montag, 26. April 2010

5.
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

6.
Benefits
Asynchronous programming
Event-loops instead of threads
Non-blocking
1 Thread (No context switching etc.)
Montag, 26. April 2010

7.
CommonJS
Montag, 26. April 2010

8.
CommonJS
A collection/library of standards
Modules
Binary
File system
and many more!
Montag, 26. April 2010

9.
CommonJS Modules
There should be a function require
There should be a var called exports
Montag, 26. April 2010

10.
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

11.
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

12.
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

13.
WebSockets
Montag, 26. April 2010

14.
WebSockets
A HTML5 standard
Allows bidirectional communications
Less overhead than HTTP/AJAX (less
headers)
Cross domain
Montag, 26. April 2010

15.
Polling
Client Mailman Server
Montag, 26. April 2010

16.
Bidirectional
Client Telephone Server
Montag, 26. April 2010

17.
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

18.
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

19.
Demo!
Montag, 26. April 2010