1. 2017, Fall Pusan National University Ki-Joune Li
Node.js
2017, Fall
Pusan National University
Ki-Joune Li

2. Server Side Programming
Client Side
Server Side
HTTP request
Web Client – Browser
(JavaScript)
Web Server
HTTP response
(HTML, CSS, JavaScript, JSON, XML, etc..)
ASP.NET,
PHP,
Node.js, etc..

3. Basic Concepts Node.js Node.js can A Node.js file operates on
uses JavaScript on the server
is an open source server framework and free
runs on various platforms (Windows, Linux, Unix, Mac OS X, etc.)
Node.js can
generate dynamic page content
create, open, read, write, delete, and close files on the server
collect form data
add, delete, modify data in your databases
A Node.js file operates on
Certain events (e.g. access a port on the server)
Activation on the server before having any effect,
Node.js file has an extension “.js”

4. Asynchronous protocol of node.js
Synchronous programming
Server Side
Client Side
Web Server
1. HTTP request (e.g. read a file)
Web Client
2. Wait the next request
and process it
4. HTTP response
5. Get the results
If the server waits only the request from one single client, it is excellent. Otherwise, the waiting is a waste of resources and multi-thread is required (not memory efficient)

5. Asynchronous protocol of node.js
Asynchronous programming
Message queue (mailbox)
Server Side
Client Side
Web Server
1. HTTP request (e.g. read a file)
Web Client
2. Read next request and process it when ready
3. HTTP response
4. Get the results
No reason to wait at the server side, which improves the total utilization of server. Single thread and memory efficient.

6. Node.js installation and running a server
You have to install Node.js® - JavaScript runtime environment
Initiate your web server
var http = require('http'); http.createServer(function (req, res) {     res.writeHead(200, {'Content-Type': 'text/html'});     res.end('Hello World!'); }).listen(8080)
'Hello World' when there is any access to port 8080

7. Message queue (mailbox)
Example: myfirst.js
Message queue (mailbox)
myfirst.js
Web Browser
Web Server
1. HTTP request (simple access)
Web Client
2. Read from 8080 port
next request and make “hello world!” html message
3. HTTP response
4. Get the html message

8. Node.js Modules Node.js provides a set of built-in modules
Descritpion
assert
Provides a set of assertion tests
buffer
To handle binary data
child_process
To run a child process
cluster
To split a single Node process into multiple processes
crypto
To handle OpenSSL cryptographic functions
dgram
Provides implementation of UDP datagram sockets
dns
To do DNS lookups and name resolution functions
domain
Deprecated. To handle unhandled errors
events
To handle events fs
To handle the file system
http
To make Node.js act as an HTTP server
https
To make Node.js act as an HTTPS server.
net
To create servers and clients os
Provides information about the operation system
path
To handle file paths
punycode
Deprecated. A character encoding scheme
querystring
To handle URL query strings
readline
To handle readable streams one line at the time
stream
To handle streaming data
string_decoder
To decode buffer objects into strings
timers
To execute a function after a given number of milliseconds
tls
To implement TLS and SSL protocols
tty
Provides classes used by a text terminal
url
To parse URL strings
util
To access utility functions v8 vm
To compile JavaScript code in a virtual machine
zlib
To compress or decompress files
Node.js provides a set of built-in modules
To include a module
var http = require('http');

9. HTTP Module
Module that allows to transfer data via http as we have already seen
var http = require('http'); http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});     res.end('Hello World!'); }).listen(8080)
'Hello World' when there is any access to port 8080
Web Browser
Web Server
1. HTTP request (simple access)
Web Client
2. HTTP response

10. File System Module
Module that allows you to work with the file system on your computer.
Read files
Create files
Update files
Delete files
Rename files
var fs = require('fs');
Client Side
Server Side
HTTP request
Web Client – Browser
(JavaScript)
Web Server
File System
HTTP response
var http = require('http'); var fs = require('fs'); http.createServer(function (req, res) {   fs.readFile('demofile1.html', function(err, data) {     res.writeHead(200, {'Content-Type': 'text/html'});     res.write(data);     res.end();   }); }).listen(8080)

11. File System Module Functions fs.appendFile() fs.open() fs.writeFile()
fs.unlink()
fs.rename
var fs = require('fs'); fs.appendFile('mynewfile1.txt', 'Hello content!', function (err) {   if (err) throw err;   console.log('Saved!'); });

12. Event Module Module that allows to handle events
To create, fire, or listen on events
var events = require('events'); var eventEmitter = new events.EventEmitter();
var events = require('events'); var eventEmitter = new events.EventEmitter(); //Create an event handler: var myEventHandler = function () {   console.log('I hear a scream!'); } //Assign the event handler to an event: eventEmitter.on('scream', myEventHandler); //Fire the 'scream' event: eventEmitter.emit('scream');