Internet Applications Development

Lecture 1

L. Obead Alhadreti

Quick Look..

• This course deals with different types of technologies (introductory course): HTML , CSS, HTML , PHP, Web Databases and more.

• This course is to build real Web sites on browsers/servers.

• This course is an introduction to basic technologies of creating

• and processing content on Internet Web sites.• It is not meant to be a comprehensive guide to any of

the areas• covered.

Quick Look..

• Marks Grading:• 10 marks attendance and participation. • 10 marks project.• 30 marks midterm exam.• 50 marks final exam.

Lecture Outline:

• The Networks.• The Internet.• The Internet Protocol.• The World Wide Web.• Web application.

The Network

The definition of the Network:A network can be defined as a collection of computers connected together with an objective of sharing resources.

The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

Networks Types

The network, according to the way of use can be divided essentially Into:

• Client-Server Paradigm• Peer-to-Peer Paradigm

Client-Server The client and server are the end systems also known as Hosts. The Client initiates contact with the server to request for a service.

• Client a computer connected to the network. Has no authorities in relation to the network. Only use the services introduced by the server.

• Server a computer provides services to the clients and control the network .

Peer-to- Peer In the network, a peer can come anytime and leave the network anytime. So a peer can be a Client or Server. So the Scalability is the advantage in this peer to peer network.

Networks Types

The network, according to the distance between the computer can be divided Into:

• Local Area Network (LAN) • Metropolitan Area Network (MAN) • Wide Area Network (WAN)

Local Area Network• A Local Area Network (LAN) is a network that is confined to a

relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. Rarely are LAN computers more than a mile apart.

• In a typical LAN configuration, one computer is designated as the file server. It stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network. Computers connected to the file server are called workstations. The workstations can be less powerful than the file server, and they may have additional software on their hard drives. On most LANs, cables are used to connect the network interface cards in each computer.

Metropolitan Area Network• A Metropolitan Area Network (MAN) covers larger geographic

areas, such as cities or school districts. By interconnecting smaller networks within a large geographic area, information is easily disseminated throughout the network. Local libraries and government agencies often use a MAN to connect to citizens and private industries.

• One example of a MAN is the MIND Network located in Pasco County, Florida. It connects all of Pasco's media centers to a centralized mainframe at the district office by using dedicated phone lines, coaxial cabling, and wireless communications providers.

Wide Area Network• Wide Area Networks (WANs) connect larger geographic

areas, such as Florida, the United States, or the world. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of network.

Advantages of Networks

• Speed• Saving Cost• Centralized Software Management• Resources sharing• Flexible Access

Disadvantages of Networks

• Rapid Spread of Computer Viruses• Expensive Set Up• Dependency on the Main File Server• Network fault can cause loss of data.

Network Architecture

• Network architecture is the design of a communications network.

• The standard model for network architecture is the Open Systems Interconnection (OSI) model that consisted of seven layers.

• A layer is a collection of similar functions that provide services to the layer above it and receives services from the layer below it. On each layer, an instance provides services to the instances at the layer above and requests service from the layer below.

• Layer 7: Application Layer Defines interface to user for communication and data

transfer in network Provides standardized services such as email, file

transfer, remote access.

• Layer 6:Presentation Layer Responsible for making sure the data will be sent the

between dissimilar systems Encodes and decodes data; Encrypts and decrypts data;

Compresses and decompresses data

• Layer 5:Session Layer Manages user sessions and dialogues by making, keeping

and ending connection.

• Layer 4:Transport Layer Manages end-to-end message delivery in network Provides reliable and sequential packet delivery through

error recovery and flow control mechanisms

• Layer 3:Network Layer Determines how data are transferred between network

devices Routes packets according to unique network device

addresses Provides flow and congestion control to prevent network

resource depletion

• Layer 2:Data Link Layer Defines procedures for operating the communication

links Frames packets Detects and corrects packets transmit errors

• Layer 1:Physical Layer Defines physical means of sending data over network

devices Interfaces between network medium and devices Defines optical, electrical and mechanical characteristics

The Internet

The Definition of the Internet:

The Internet is a collection of various networks that can communicate with one another through a protocol called Transmission Control Protocol/ Internet Protocol (TCP/IP) to serve billions of users worldwide.

International Network = Internet

The largest network of networks in the world.

The history of the Internet• It all begins during the cold war between the soviet union and

the united states. • 1957: the soviet union developed a satellite to transfer information. • 1960: Advanced Research Projects Agency (ARPA) in the United

States, developed ARPA net.• 1969: ARPA net was connected to many American universities. • 1970: The internet was used in Europe.• 1972: electronic email appeared.• 1980: the internet was widely used.• 1992: the World Wide Web appeared. • 1993: Web browser appeared. .(Mosaic browser)

Internet Usage Statistics

The Intranet & Extranet• The Intranet is an internal and local network. Used the technology of internet in an

isolated environment. e.g. A special network for the company to exchange information and data.

• The Extranet is expanded local network. grant some of the clients the capabilities to

use them through secure gates.

Internet Architecture

1. network layer: concerned with physical connection between nodes.

2. internet layer: deals with addressing and fragmentation of packets (includes ICMP).

3. transport layer: provides reliable connections (for TCP) between processes on hosts.

4. application layer: contains protocols used by applications.

Internet Protocols

• A protocol is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols specify interactions between the communicating entities.

Internet Protocol (IP)

• the Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet.

• Responsible for transmitting blocks of data (packets) from sources to destinations.

• Each packet has 32-bit destination address (IP address) 4 bytes written as n1.n2.n3.n4 where each ni is a decimal number, e.g., 18.23.0.22.

Transmission Control Protocol (TCP)

• TCP (Transmission Control Protocol) is a set of rules (protocol) used along with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet.

• While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.

• For example, when an HTML file is sent to you from a Web server, the Transmission Control Protocol (TCP) program layer in that server divides the file into one or more packets, numbers the packets, and then forwards them individually to the IP program layer. Although each packet has the same destination IP address, it may get routed differently through the network. At the other end (the client program in your computer), TCP reassembles the individual packets and waits until they have arrived to forward them to you as a single file.

TCP Features• acknowledges safe receipt of packets• detects missing/corrupted/duplicated packets• provides method to resend missing/corrupted packets• uses sequence numbers to reassemble packets in same order as

sent• so looks like stream from application's viewpoint

User Datagram Protocol (UDP)

• the User Datagram Protocol (UDP) is one of the core members of the Internet Protocol.

• With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths. The protocol was designed by David P. Reed in 1980.

• UDP provides connectionless, unreliable service so • UDP faster than TCP

• Simple Mail Transfer Protocol (SMTP)

• (pronounced as separate letters) Short for Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers. Most e-mail systems that send mail over the Internet use SMTP to send messages from one server to another; the messages can then be retrieved with an e-mail client using either POP or IMAP. In addition, SMTP is generally used to send messages from a mail client to a mail server. This is why you need to specify both the POP or IMAP server and the SMTP server when you configure your e-mail application.

• File Transfer Protocol (FTP)

• File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. It is often used to upload web pages and other documents from a private development machine to a public web-hosting server.

• Network News Transfer Protocol (NNTP)

• The Network News Transfer Protocol (NNTP) is an Internet application protocol used for transporting Usenet news articles (netnews) between news servers and for reading and posting articles by end user client applications

Domain Name System (DNS)• DNS stands for Domain Name System. This system is in place to

organize and identify domains. Essentially, DNS provides a name for a domain's one or more IP addresses. Websites have both a "friendly" address, called a Uniform Resource Locator (URL) and an IP address. People use URLs to find websites, but computers use IP addresses to find websites. DNS translates URLs into IP addresses (and vice versa). For example, if you type http://www.microsoft.com into the address bar in your web browser, your computer sends a request to a DNS server. The DNS server translates the URL into an IP address so that your computer can find the Microsoft web server.

The Internet ConnectionTo connect to the Internet, you will need to:1. TCP/IP.2. Connection unit (e.g. Modem).3. Communication lines.4. Internet services provider (ISP)5. Internet browser (e.g. Internet explorer).

Types of Communication lines

1. PSDN PSDN or Public Switched Data Network is simply the technical name for the telephone

system in use today.

2. ISDN Stands for "Integrated Services Digital Network." ISDN dates back to 1984, and allows

much faster transfer rates than when using modems. Using ISDN, you can transfer 64K or 128K of data per second.

3. Satellites Satellite communications makes it possible for you to make a telephone callor access the internet from almost anywhere on the planet. Very Expensive.

Modem

• The modem is advice that transform the analog signals into digital signals and vice versa.

• The computer deals with the digital signals while the telephone lines deals with the analog signals.

Main Uses of the Internet

• The electronic mail (e-mail)

is one of the most commonly used application. it is an electronic copy of the ordinary mail. It is free. Developed in 1972. used to send messages anywhere in the world. Used a protocol called SMTP.

User-name@ server-name

Example: AAA@ hotmail.com

• File Transfer (FTP)Enable its users to upload and download the files, which help researcher to transfer data through the network. Used File transfer protocol (FTP).

• Internet relay chatEnables its users to chat with one another. Can be done bywriting, sound, pictures, videos. It assist in distance learning.

• E-learning The internet is used as a medium to deliver the educationcontent to students regardless of their geographical location.

• E-commerceThe Internet is used by companies to expand their business and to present information regarding their goods.

• Entertainment Internet users can play games online. They can also watch plays and movies.

• Internet Radio Stations Internet users can listen to the radio station while using the

Internet.

• The world wide web (WWW)

• The World Wide Web is a collection of electronic documents linked together like a spider web. These documents are stored on computers called servers located around the world. It is the most common service. Developed in 1992. by tim breners. It is a huge hyper text documents. Depends on a protocol called Hyper Text Transfer

Protocol (HTTP).it is used to get information in various forms, e.g. sound, visual, and written form.

The advantages of www pages Non-linearity Interactivity Grpahical interfaces

• HTTP

• The Hypertext Transfer Protocol (HTTP) is an protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.

• web clients (browsers) contact web servers requesting documents. • interaction between client and server has 4 phases:

1. client connects to server2. client sends request to server3. server sends response to client4. server closes connection

• HTTP Client Requests• each client request message has the format: method URL-path HTTP-version (request-line) headers (0 or more lines) <blank line> (CRLF) message-body (only if a POST method) Request methods: • GET: request document named by URL-path • HEAD: return only header information of URL-path (e.g., test for validity, recent

modification)• POST: submit information to entity given by URL-path

• example of a request-line: • GET /index.html HTTP/1.0 URL-path includes optional query and fragment identifier form of each header is

field: value, e.g. User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)

• HTTP Server Responses

• each server response message has format: HTTP-version status-code reason-phrase (status-line) headers (0 or more lines) <blank line> (CRLF) message-body

• example of status-line: HTTP/1.0 200 OK

• Common Gateway Interface

• The common gateway interface (CGI) is a standard way for a Web server to pass a Web user's request to an application program and to receive data back to forward to the user.

• When the user requests a Web page (for example, by clicking on a highlighted word or entering a Web site address), the server sends back the requested page. However, when a user fills out a form on a Web page and sends it in, it usually needs to be processed by an application program. The Web server typically passes the form information to a small application program that processes the data and may send back a confirmation message. This method or convention for passing data back and forth between the server and the application is called the common gateway interface (CGI). It is part of the Web's Hypertext Transfer Protocol (HTTP).

Uniform Resource Locator (URL)

• A URL (Uniform Resource Locator, previously Universal Resource Locator) is the unique address for a file that is accessible on the Internet. • A common way to get to a Web site is to enter the URL of its home page file in

your Web browser's address line. However, any file within that Web site can also be specified with a URL. Such a file might be any Web (HTML) page other than the home page, an image file, or a program.

• The URL contains the name of the protocol to be used to access the file resource, a domain name that identifies a specific computer on the Internet, and a pathname, a hierarchical description that specifies the location of a file in that computer.

• On the Web (which uses the Hypertext Transfer Protocol, or HTTP), an example of a URL is:

http://www.google.com.sawww.google.com.sa domain name

Web application development Process

• A web application is an application that is accessed over a network such as the Internet or an intranet. The application can be as simple as a message board or a guest sign-in book on a website, or as complex as a word processor or a spreadsheet

Web application development Process

Web application development process is the process and practice of developing web applications.

There are various types of Lifecycle Model, such as:• Waterfall lifecycle• Prototype lifecycle• Agile

Waterfall

Web application development Process

1. Requirement Analysis and Development Plan Site Architecture. Text-only Site Framework—Content, site map, site navigation.

2. Visual Communication and Artistic Design— Page layout, Homepage/entry page.

3. Site Production— Page Client-side programming, Server-side programming, Finished pages.

4. Testing Error checking and validation.

5. Deploying; Documentation; Maintenance.

Internet programming Languages

There are two types of Internet programming Languages

1. Client-side programming languages, such as HTML , java script.

2. Server-side programming languages, such as ASP , JSP, PHP