MySQL and PHP Internet and WWW
Jan 13, 2016
MySQL and PHP
Internet and WWW
Computer Basics
Laptop computer Desktop PC
Server
Flat screen
PrinterScanner
Keyboard
A Single Computer
Tower box
Flat screen
Scanner
Printer
Tape drive
CD burner
Keyboard Mouse
Network Architecture• Client/Server Architecture (two-tier architecture): each
computer on the network is either a client or a server (some computers can be both client and server but not at the same time).– Dedicated Servers: such as file servers (managing disk drives),
print servers (managing printers), network servers (managing network traffic).
– A client is defined as a requester of services.– A server is defined as the provider of services.
• Peer-to-peer Architecture (P2P): each computer on the network has equivalent capabilities and responsibilities.
Client/Server
File/DB Server
Desktop PC
Workstation Laptop computer
Print Server
Floppy drive
Tape drive
Database
Printer
Printer
Printer
CD burner
Scanner
Network
Local Area Network (LAN)
• A Local Area Network (LAN) is a group of computers and devices that share a common communications line or wireless link and typically share the resources of a server within a small geographic area (for example, within an office building).
Wide Area Network (WAN)
• A Wide Area Network (WAN) is a computer network covering a wide geographical area, involving a lot more computers. This is different from Local Area Network (LAN) that is usually limited to a room, building or campus. The most well-known example of a WAN is the Internet.
• WANs are used to connect Local Area Networks (LANs) together.
History of Internet
• In the late 1950s, the US government formed the Advanced Research Projects Agency (ARPA).
• During the 1960s, the agency created a decentralized computer network known as ARPAnet.
• This network linked four computers located at the UCLA, Stanford Research Institute, the UC Santa Barbara, and the University of Utah.
New Technologies
• Packet switching (communication still function even if some nodes would be destroyed by a nuclear attack).
• Email was implemented in 1972• Telnet Protocol for logging on to remote computers• File Transfer Protocol (FTP)• In 1989, Tim Berners-Lee and his colleagues at the European
particle physics laboratory CERN proposed the concept of linking documents with hypertext. (World Wide Web)
• In 1993, the introduction of Mosaic, the first graphical web browser (Netscape Navigator)
The World Wide Web
• The WWW operates using a client/server networking principle.
• When you enter the URL (the web address) of a web page into your browser and click “Go”.
• You ask the browser (client) to make an HTTP request to the particular computer having that address.
• That computer (server) returns the required page to you in a form that your browser can interpret and display.
How does Internet work?
http://www.mywebpage.com/index.html
• The browser broke the URL (Uniform Resource Locator) into three parts:– The protocol (“http”)– The server name (‘WWW.mywebpage.com”)– The file name (“index.htm”)
• The browser communicated with a name server to translate the server name www.mywebpage.com into an IP address, which it uses to connect to the server machine.
• The browser then formed a connection to the server at that IP address on port 80.• Following the HTTP protocol, the browser sent a GET request to the server, asking for
the file http://www.mywebpage.com/index.htm (cookies may be sent from browser to server with the GET request)
• The server then sent the HTML text for the web page to the browser (cookies may also be sent from server to browser in the header for the page)
• The browser read the HTML tags and formatted the page onto your screen.
The Internet• The Internet is a gigantic collection of millions of computers, all
linked together on a computer network. • A home computer may be linked to the internet using a phone-line
modem, DSL or cable modem that talks to an Internet service provider (ISP).
• A computer in a business or university will usually have a network interface card (NIC) that directly connects it to a local area network (LAN) inside the business.
• The business can then connect its LAN to an ISP using a high-speed phone line such as a T1 line.
• ISPs then connect to larger ISPs, and the largest ISPs maintain fiber-optic “backbones” for an entire nation or region.
• Backbones around the world are connected through fiber-optic lines, undersea cables or satellite links.
The Internet
The Internet
The Internet
A map of domain name ownership at street level for downtown San Francisco
The Web Server
• The Web server is not simply “looking up a file”.• It is actually processing information and generating a
page based on the specifics of the query. • Dynamic web pages are generated by software such
as CGI (Common Gateway Interface) scripts.• Web server
– Microsoft IIS (Internet Information Services)– Apache
The Browser
• There are different web browsers in the market.
• Mozilla – Firefox for Windows & Linux• Microsoft - Internet Explorer for Windows • Netscape for Windows• Opera for mobile phones• Safari for Apple
What is?• Web Pages: contain HTML coding.• Web Site: a collection of web pages.• Web servers: Program that interpret HTTP requests and deliver the appropriate web page to your
browser.• Server-Side Programming: Programs that run on the server computer.• Web Browsers: Program on the client computer that use to interpret and display web pages.• Client-Side Programming: Programs that run on the client side.• DNS (Domain Name Service): Convert Domain name into IP address.• HTTP Requests: transmit from browser to server with method information (GET/POST) to request a
web page.• HTTP Responses: return from server to browser with status codes (200 – ok, 204 – no content, 401 –
not authorized, 403 – forbidden, 404 – not found, etc…)• HTML Forms: web page contain fields where you can enter information. (<form></form>, <input />,
<select></select>, <option></option>, etc…)• GET and POST Requests:
– GET: encodes the message it sends into a query string, which is appended to the URL .– POST: sends its message in the message body of the request. (data is encoded and sent via an
HTTP request).