Tiêu đề All Units Notes - WT.pdf ✅

1 - Introduction Prof. Arjun Bala, CE Department | 2160708 – Web Technology 2 protocols. So we can says that Internet is network of computer which connect to together and any computer communicate with any other computer. What is The Web (World Wide Web)?  The World Wide Web, or simply Web, is a way of accessing information over the medium of the Internet. It is an information-sharing model that is built on top of the Internet.  The Web uses the HTTP protocol, only one of the languages spoken over the Internet, to transmit data. The Web also utilizes browsers, such as Internet Explorer or Firefox, to access Web documents called Web pages that are linked to each other via hyperlinks. Web documents also contain graphics, sounds, text and video. Different between Internet and WWW  The Web is a Portion of The Internet. The Web is just one of the ways that information can be disseminated over the Internet. The Internet, not the Web, is also used for email, which relies on SMTP, Usenet news groups, instant messaging and FTP. So the Web is just a portion of the Internet. HTTP Protocol: Request and Response.  HTTP stands for Hypertext Transfer Protocol.  HTTP is based on the client-server architecture model and a stateless request/response protocol that operates by exchanging messages across a reliable TCP/IP connection.  An HTTP "client" is a program (Web browser) that establishes a connection to a server for the purpose of sending one or more HTTP request messages. An HTTP "server" is a program (generally a web server like Apache Web Server) that accepts connections in order to serve HTTP requests by sending HTTP response messages.  Errors on the Internet can be quite frustrating — especially if you do not know the difference between a 404 error and a 502 error. These error messages, also called HTTP status codes are response codes given by Web servers and help identify the cause of the problem.  For example, "404 File Not Found" is a common HTTP status code. It means the Web server cannot find the file you requested. The file -- the webpage or other document you try to load in your Web browser has either been moved or deleted, or you entered the wrong URL or document name.  HTTP is a stateless protocol means the HTTP Server doesn't maintain the contextual information about the clients communicating with it and hence we need to maintain sessions in case we need that feature for our Web-applications  HTTP header fields provide required information about the request or response, or about the object sent in the message body. There are four types of HTTP message headers: o General-header: These header fields have general applicability for both request and response messages. o Request-header: These header fields have applicability only for request messages. o Response-header: These header fields have applicability only for response messages. o Entity-header: These header fields define Meta information about the entity-body.
1 - Introduction Prof. Arjun Bala, CE Department | 2160708 – Web Technology 3  As mentioned, whenever you enter a URL in the address box of the browser, the browser translates the URL into a request message according to the specified protocol; and sends the request message to the server.  For example, the browser translated the URL http://www.test101.com/doc/index.html into the following request message: GET /docs/index.html HTTP/1.1 Host: www.test101.com Accept: image/gif, image/jpeg, */* Accept-Language: en-us Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) Here,Step by step communication between client and server mention into followingfigure. Fig 1: Communication between HTTP Client and HTTP Server Web Browser and Web Server.  Web server and web browser are the terms which are commonly used for website. The basic purpose of both is to develop a platform for internet web directory. So that any users can anytime access any kind of website. Major difference between them is on their function and how they perform their functions. Check for the detail of both topics before understanding the differences between them. Web Browser  Web browser is a client, program, software or tool through which we sent HTTP request to web server. The main purpose of web browser is to locate the content on the World Wide Web and display in the shape of web page, image, audio or video form.
1 - Introduction Prof. Arjun Bala, CE Department | 2160708 – Web Technology 4  We can also call it a client server because it contacts the web server for desired information. If the requested data is available in the web server data then it will send back the requested information again via web browser.  Microsoft Internet Explorer, Mozilla Firefox, Safari, Opera and Google Chrome are examples of web browser and they are more advanced than earlier web browser because they are capable to understand the HTML, JavaScript, AJAX, etc. Now days, web browser for mobiles are also available, which are called micro browser. Web Server  Web server is a computer system, which provides the web pages via HTTP (Hypertext Transfer Protocol). IP address and a domain name is essential for every web server.  Whenever, you insert a URL or web address into your web browser, this sends request to the web address where domain name of your URL is already saved. Then this server collects the all information of your web page and sends to browser, which you see in form of web page on your browser.  Lot of web server software is available in the market in shape of NCSA, Apache, Microsoft and Netscape. Storing, processing and delivering web pages to clients are its main function. All the communication between client (web browser) and server takes place via HTTP.  Here, we can easily understand concept of web browser and web server by following figure. Fig 2: Communication between web Browser and Web Server Feature of Web 2.0.  Web 2.0 is term that was introduced in 2004 and refers to the second generation of the World Wide Web.The term "2.0" comes from the software industry, where new versions of software programs are labeled with an incremental version number.  Some examples of features considered to be part of Web 2.0 are listed below: o Blogs : It also known as Web logs, these allow users to post thoughts and updates about their life on the Web. o Wikis: Wikis - sites like Wikipedia and others enable users from around the world to add and update online content. o Social Networking: