A short intro about node.js and websockets. You can find the demostration at http://github.com/kompozer/tweamer

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
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16. Bidirectional
Client Telephone Server
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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