INT222Internet I - Internet Fundamentals

Week 1

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Outline

• Course Overview• Internet Architecture• Introduction to JavaScript • Demo

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Course Overview

• Course outlinehttps://scs.senecac.on.ca/course/int222

• Course standardshttp://wsong18.wordpress.com/standards/

• Academic Honesty Policyhttps://scs.senecac.on.ca/page/academic-honesty-policy

• In this course, you will learn web client (front-end) development concepts and techniques, using JavaScript, HTML and the DOM, and CSS.

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Evaluation

6 labs (1 % or 2% each) 10% 3 quizzes (1.5% or 2% each ) 5%3 assignments (6% + 6% + 8%=) 20%2 term tests (17% + 18%=) 35% Final exam

30%----------------------------------------------------Total 100%

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Promotion Policy

To obtain a credit in this subject, a student must:• Achieve a grade of 50% or better on the final

exam• Satisfactorily complete all assignments• Achieve a weighted average of 50% or better

for the tests and final exam• Achieve a grade of 50% or better on the

overall course

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Communication

• Blackboard• My web site:

http://wsong18.wordpress.com/

• INT222 course sitehttps://zenit.senecac.on.ca/~emile.ohan/int222/weekly.html

• Email:wei.song@senecacollege.ca

• Student help hours:http://zenit.senecac.on.ca/~wei.song/

• Office room: Tel -2101

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Coordinate with other sections

• Common assignments• Common labs (but different due dates)• Common final exams• Similar term tests• Similar quizzes?• Matched lectures– Lecture Slides on my web page– Weekly Notes on INT222 site

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Expectation

• Mine:– Be present. Practice.– Learning strategy:• Getting the big picture (concepts, framework,

architecture)• paying attention to the details (coding, syntax, hands-

on)• Memorizing something!

• Yours?

Introduce to Internet architecture

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About the Internet architecture

• The Internet’s architecture is described in its name, a short form of the compound word “inter-networking”.

• This architecture is based in the very specification of the standard TCP/IP protocol, designed to connect any two networks which may be very different in internal hardware, software, and technical design.

• Once two networks are interconnected, communication with TCP/IP is enabled end-to-end, so that any node on the Internet has the near magical ability to communicate with any other no matter where they are. This openness of design has enabled the Internet architecture to grow to a global scale.

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The Internet map : router-based interconnectivity

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The Internet Reference Model and the protocol stack

• We may mainly deal with application (layer) protocols.

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Internet application protocols• Remote login category

– Telnet– SSH, Secure Shell

• File transfer category– FTP, File Transfer Protocol– TFTP, Trivial File Transfer

Protocol• Support services category

– DNS, Domain Name System– SNMP, Simple Network

Management Protocol– CMOT, Common Management

Information Protocol

•Electronic mail category– SMTP, Simple Mail Transfer Protocol– IMAP, Internet Message Access

Protocol– POP, Post Office Protocol•Other protocols─ HTTP, HyperText Transfer Protocol─ HL7, Health Level Seven─ LDAP, Lightweight Directory Access

Protocol─ NFS, Network File System─ DHCP, Dynamic Host Configuration

Protocol─ IRC, Internet Relay Chat─ …

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A port number is reserved for each the services on a server

• FTP (file transfer protocol) - usually on port 21• SFTP (Secure file transfer protocol) - usually on

port 22• SSH (Secure Shell) - used for secure logins -

usually on port 22• telnet - usually on port 23• http - usually on port 80

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Services provided by the Internet• World Wide Web (the Web )

– It is a collection of web pages connected through hyperlinks and URLs.

– It is governed by the Hyper Text Transfer Protocol (HTTP) that deals with the linking of files, documents and other resources of the web.

• Electronic Mail (email)• Mailing List• File Transfer Protocol (FTP)• Instant Messaging• News Groups• Chat Rooms• Chat

HyperText Transfer Protocol

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What is HTTP

• HTTP, the Hypertext Transfer Protocol, is the application-layer protocol that is used to transfer data on the (World Wide ) Web.

• HTTP comprises the rules governing the format and content of the conversation between a web client and server.

• HTTP functions as a request-response protocol in the client-server computing model. – It follows a classical client-server model, with a client opening a

connection, making a request then waiting for a response until it receives it.

• HTTP is stateless.– The server doesn't keep any data (state) between two requests.

• Latest version is HTTP 1.1

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HTTP transaction

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HTTP Request and response messages

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Structure of the HTTP request• A HTTP (client) request consists of text directives,

divided in three blocks:1. The first/request line contains a request method, the

HTTP protocol version used, followed by the path of the document.

2. The subsequent block represents specific request headers• Gives the server some information about what kind of data is

appropriate (e.g., what language, what MIME types) or some data altering its behavior (e.g., not sending an answer if it is already cached).

• This block ends with an empty line.

3. The final block is the optional data block/request body.• Contains further data and is mainly used by the POST method.

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An example of HTTP requests

• Fetching the root page of developer.mozilla.org, i.e. http://developer.mozilla.org/, and telling the server that the user-agent would prefer the page in French, if possible:

GET / HTTP/1.1 Host: developer.mozilla.org Accept-Language: fr

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Another example

• Sending the result of a form:

POST /contact_form.php HTTP/1.1 Host: developer.mozilla.org Content-Length: 64 Content-Type: application/x-www-form-urlencoded

name=Joe%20User&request=Send%20me%20one%20of%20your%20catalogue

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HTTP request methods

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Structure of a server response• Similarly to a client request, a server response

is formed of text directives, divided in three different blocks:1. The first block, the status line, consists of an

acknowledgment of the HTTP version used, followed by a response status codes.

2. The subsequent block contains response headers, giving the client some information about the data sent and ends with an empty line.

3. The final block is the data block/response body, which contains the data (if any).

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An example of server responses

• Successful reception of a web page:HTTP/1.1 200 OK Date: Sat, 09 Oct 2010 14:28:02 GMT Server: Apache Last-Modified: Tue, 01 Dec 2009 20:18:22 GMT ETag: "51142bc1-7449-479b075b2891b" Accept-Ranges: bytes Content-Length: 29769 Content-Type: text/html

<!DOCTYPE html... (here comes the 29769 bytes of the requested web page)

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Another example

• A server notification that the requested resource doesn't exist:

HTTP/1.1 404 Not Found

Date: Sat, 09 Oct 2010 14:33:02 GMT

Server: Apache

Last-Modified: Tue, 01 May 2007 14:24:39 GMT

ETag: "499fd34e-29ec-42f695ca96761;48fe7523cfcc1"

Accept-Ranges: bytes

Content-Length: 10732

Content-Type: text/html

<!DOCTYPE html... (contains a site-customized page helping the user to find the missing resource)

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HTTP response status codes

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HTTP header fields

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HTTP Secure

• Hypertext Transfer Protocol Secure (HTTPS) is a communications protocol for secure communication over a computer network, with especially wide deployment on the Internet.

• Technically, it is not a protocol in and of itself; rather, it is the result of simply layering the Hypertext Transfer Protocol (HTTP) on top of the SSL(Secure Sockets Layer)/TLS(Transport Layer Security) protocol, thus adding the security capabilities of SSL/TLS to standard HTTP communications.

Web Technology

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Web Technology Basic • The World Wide Web is a system of interlinked hypertext documents

accessed via the Internet. The two basic components of the Web are the Web browser client and the Web server.

• Three fundamental elements comprise the technology architecture of the Web:– Uniform Resource Locators (URL)

• A standard syntax used for creating identifiers that point to Web-based resources.• eg. https://zenit.senecac.on.ca/~int222_141a45/index.html

– protocol = https://– domain name = zenit.senecac.on.ca– path or URI - uniform resource indicator = ~int222_141a45/index.html

– Hypertext Transfer Protocol (HTTP) • This is the primary communications protocol used to exchange content and data

throughout the World Wide Web. URLs are typically transmitted via HTTP.

– Markup Languages (HTML, XML) • Markup languages provide a lightweight means of expressing Web-centric data and

metadata. The two primary markup languages are HTML (which is used to express the presentation of Web pages) and XML (which allows for the definition of vocabularies used to associate meaning to Web-based data via metadata).

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Web Applications

• A distributed application that uses Web-based technologies (and generally relies on Web browsers for the presentation of user-interfaces) is typically considered a Web application.

• These applications can be found in all kinds of cloud-based environments due to their high accessibility.

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The common architectural abstraction for Web applications

• It is based on the basic three-tier model. – The first tier is called

the presentation layer, which represents the user-interface. • The presentation layer has

components on both the client and server-side.

– The middle tier is the application layer that implements application logic.

– The third tier is the data layer that is comprised of persistent data stores.

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Front-end web application

• The rising popularity of so-called “modern” web apps means that web developers are focusing on writing more and more front-end, or client-side code. Although back-end, or server-side code still plays an important factor, the fact is that web developers are working more directly with HTML5, CSS3, and JavaScript.

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The architecture for front-end web application

• What is the front-end/client-side doing?– Render UI– Interactivity– Logical requests to server– UI state management

• What is the server-side doing? – Authority on request integrity– Accessing/updating DB– Serving data

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Web Development

• is hard. • You must know at least 3 (often 4) programming

languages:– JavaScript

•the state and behavior of the frontend

– CSS • how things look

–HTML •structure of the UI/Document

– Server Programming (INT322)• Stateful storage and interaction with other servers

Introduction to JavaScript

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What is a Script• A script is a high-level programming language that is

interpreted by another program at runtime rather than compiled by the computer's processor (as other programming languages such as C and C++ are).

• Some types of languages are client-side scripting languages, affecting the data that the end user sees in a browser window. Other scripting languages are server-side scripting languages that manipulate the data, usually in a database, on the server.

• Scripting languages came about largely because of the development of the Internet as a communications tool. JavaScript, ASP, JSP, PHP, Perl, Tcl and Python are examples of scripting languages.

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What is JavaScript?

• JavaScript (JS) is a cross-platform Web scripting language. – JavaScript always runs inside a host environment

(mostly the browser). • JavaScript is a prototype-based scripting language

with dynamic typing and has first-class functions.– There is no class in JS (constructors do what classes do). – The object-based language with prototyping: powerful

prototypal object-oriented language– In JavaScript every function is actually a Function object.

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About JavaScript

• JavaScript is one of the world's most popular programming languages .– The role as the scripting language of the WWW.– simple and easy to learn

• JavaScript is the world's most misunderstood programming language.– The name, typecasting, used by amateurs, object-

oriented,…• JavaScript is, in the future, the most important

language you will learn(? Dart?)

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JavaScript History• JavaScript was developed in 1995 by Brendan Eich at

Netscape, now a division of America Online. • JavaScript started with simple one-liners embedded in HTML.• The JavaScript backlash (incompatibility, …) caused some web

projects to completely ban any client-side programming and trust only their predictable and reliable server.

• ECMAScript (European Computer Manufacturers Association) was born, making healthier environment.

• JavaScript is now used in much more sophisticated ways. – Developers leverage the object-oriented nature of the language to

build scalable code architectures made up of reusable pieces. – JavaScript provides behavior, the third pillar in today's paradigm

• web pages consist of three clearly distinguishable parts: content (HTML), presentation (CSS), and behavior (JavaScript).

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The Present• Today, you can use JavaScript to do all of this:

– Create rich and powerful web applications (the kind of applications that run inside the web browser, such as Gmail)

– Write server-side code such as ASP scripts or, for example, code that is run using Rhino (a JavaScript engine written in Java)

– Create rich media applications (Flash, Flex) using ActionScript, which is based on ECMAScript

– Write scripts that automate administrative tasks on your Windows desktop, using Windows Scripting Host

– Write extensions/plugins for a plethora of desktop application such as Firefox, Dreamweaver, and Fiddler

– Create web applications that store information in an off-line database on the user's desktop, using Google Gears

– Create Yahoo! Widgets, Mac Dashboard widgets, or Adobe Air applications that run on your desktop

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Front-end Apps Demo

The PlanetariumBeautiful Web Introduction to the solar system

BananBreadWeb FPS shoorter

CSS TricksWeb Animation (using data from 3d body tracking)

Let’s start with JavaScript

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Firefox Scratchpad

• Why use Scratchpad?– JavaScript always runs inside a host environment (mostly the

browser). • To use Scratchpad, go to the “Web Developer” menu (hint for

Mac users: look for the “Web Developer” menu under “Tools”). Select “Scratchpad” from that menu, and you’ll get a text editor window.

• Shortcut: Shift+F4• How to run a script:

1. Enter some code 2. Select a portion of the code 3. Choose one of the three commands from the Execute

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prompt()

• This built-in function (of the Window object) will display a dialog box (Modal window) that prompts the visitor for input.

• Gets user input. Rarely used.• Example code:

var ok = prompt("Are you OK?");alert(ok);

1+2; // Instpct/display executes the selected code,

//and the result is put right into your editor.

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alert()

• Pops up an alert box (Modal window) with a message and an OK button.

• Outputs info.• Example code:

function sayHello() { alert("Hello from the Scratchpad");}

sayHello();alert("This is alert 2");alert(42);

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console.log()

• Shows a message in web console.• Outputs info.• Example code:

var someObject = { str: "Some text", id: 5 }; console.log(someObject);

• View log:– Ctrl + Shift + J to open browser console.

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Create/edit/save the source code

• Although web client programming allows us to place JavaScript inline or internal to a document , we prefer that you store your JavaScript code in its own source code file.

• You can use any text editor, Scratchpad or programmer’s editor.

• We suggest that you store your code in the xxx/js folder, and name each source code file by using a .js extension.

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LET’S TAKE A LOOK AT SOME SYNTAX

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JavaScript is a C-family/style language

• A rich set of operators are available, using a comfortable C-like syntax.

• Statements should end with a ; semicolon, just like in C.• Expressions are also similar to C, and you can use

operators on objects without conversions.• Curly braces { } are used as code block delimiters.

Scoping follows rules similar to C (but are different, as you will learn).

• Similar to C, if-else (including the ? : syntax) and switch-case are available in JS.

• for and while are available in JS.

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Comments and more

• JavaScript supports two kinds of comments: – A block comment starting with /* and ending with

*/ that may span several lines. • (This is the same form as a CSS comment.)

– A line comment that starts with // and goes to the end of the line.

• JavaScript is case-sensitive

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Declare and Refer Variables

• You must use the “var” keyword to precede a variable name.

• Unlike the C language, you do not need a type specifier. – The variable’s initial value will set its initial type.

• Declaration syntax:var variableName;var variableName = value;// Referring to and using syntax:variableName = someValue;document.write(variableName);

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Arithmetic OperatorsOperator

Operation Example

+ addition of numbersConcatenation of strings

y + x; “INT” + “222”

- subtraction x - y;

* multiplication x * y;

/ division x / y;

% modulo x % y; // remainder of x divided by y

++ post/pre -increment x = y++; // assign y to x, then increment y (y+=1) x = ++y; //increment y < (y+=1), then assign y to x

-- post/pre decrement x = y--; // assign y to x, then decrement y (y-=1) x = --y; // decrement y < (y-=1), then assign y to x

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Assigning ValuesOperator  Example Equivalent For

= a = b; a = b; numbers or strings

+= a += b; a = ( a + b); numbers or strings

-= a -= b; a = ( a - b); numbers

*= a *= b; a = ( a * b); numbers

/= a /= b; a = ( a / b); numbers

%= a %= b; a = ( a % b); // divide a by b, // assign remainder to a numbers

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Logical OperatorsOperator  Operation Example

&& Logical AND expr1 && expr2

|| Logical OR expr1 || expr2

! Logical NOT !expr1

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Other Operators

• Conditional Operator:Result = (condition)?"if true":"if false";e.g. var Grade=(mark<50)?"Fail":"Pass";

• The typeof operator (for variable or values):– possible return values:

"undefined“, "object“, "boolean“, "number“, "string“, "function“, "xml“, "object“

• The instanceof operator– …

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Comparison OperatorsOperator Description Example

==Equal

(The operands are converted to the same type before being compared.)

1 == 1 is true1 == "1" is true1 == true is true0 == false is true

===strictly equal

(There is no type conversion.)1 === 1 is true

1 === "1" is false1 === true is false0 === false is false

!= not equal(with type conversion)

1 != 1 is false1 != ‘1’ is false

!== not equal(without type conversion)

1 !== 1 is false1 !== ‘1’ is true

> greater than expr1 > expr2

>= greater than or equal to expr1 >= expr2

< less than expr1 < expr2

<= less than or equal to expr1 <= expr2

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Strings and Quotation Marks

• Literal strings can be denoted by either single or double quotes, which gives you some flexibility about how to handle awkward situations such as quotation marks inside a string:

Expression Values

"Let’s start with JavaScript” Let’s start with JavaScript

'Not "it"!' Not "it"!

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Concatenation of Strings

• The main operation on strings is the concatenation operator, +:

Expression Value

“INT" + “222" INT222

“Stephen” + “ Harper” Stephen Harper

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The prompt() Function

• Examples:var a = prompt("Enter first number"); // enter 11var b = prompt("Enter second number"); // enter 12var result = a + b;alert("The result is " + result); // What is the result?

• Default valuesvar school = prompt("What is your school?", “Seneca");alert("Oh, you go to "+school+". How nice.");

• Warning: The prompt() function does not work properly in certain browsers. So it's best not to use it in projects.

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The parseInt() and parseFloat()

• Used to convert from a string of digits to numbers.

• The second argument to parseInt() is the radix or base that you want to use.

Expression Value

parseInt("243",10) 243

parseInt("cs110",10) NaN (Not a Number)

parseFloat("3.141") 3.141

parseInt("3.141",10) 3

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Lab Practices

• Lab on the INT222 Site:– Updating your index.html– Due on:• Section D: Jan 11, 2014• Section C: Jan 16, 2014

• Practice Scratchpad

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Week 1 reading reference

• HTTP (MDN): https://developer.mozilla.org/en-US/docs/HTTP

• Firefox Developer Tool – Scracthpad (MDN): https://developer.mozilla.org/en-US/docs/Tools/Scratchpad

• (Core) JavaScript Guide (MDN): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide

• JavaScript Syntax Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements

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Thank You !

• The matched content for this slides can also be found on the INT222 Course Site Weekly Notes:1. Week 01 - January 6, 20142. Week 02 - January 13, 2014