Web Clients
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Web Clients. Chapter 2. Web Protocols and Practice. WEB CLIENTS. Topics. Web Protocols and Practice. WEB CLIENTS. Web Client Definition. Web Protocols and Practice. WEB CLIENTS. Web Client Definition. Web Protocols and Practice. WEB CLIENTS. Browser Functions.

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Web Clients

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Web clients

Web Clients

Chapter 2

WebProtocolsandPractice


Topics

WEB CLIENTS

Topics

WebProtocolsandPractice


Web client definition

WEB CLIENTS

Web Client Definition

WebProtocolsandPractice


Web client definition1

WEB CLIENTS

Web Client Definition

WebProtocolsandPractice


Browser functions

WEB CLIENTS

Browser Functions

WebProtocolsandPractice


Web clients

Browser

DNS server

WEB CLIENTS

1 DNS query

URL

Origin server

2 TCP Connection

3 HTTP Request

4 HTTP Response

5 Optional parallel connections

Figure 2.1. Steps in a browser process

WebProtocolsandPractice


Web clients

Figure 2.1 shows the various steps in the process involved in a Web request as processed by a typical browser. The selected URL is parsed to determine the Web server that must be contacted. A connection is set up with the server, and an HTTP request is sent with the URL to obtain the response.


Table 2 1 user action leading to request generation

WEB CLIENTS

Table 2.1. User action leading to request generation

WebProtocolsandPractice


Canonical web transfer example

WEB CLIENTS

Canonical Web Transfer Example

WebProtocolsandPractice


Table 2 2 resources referred to in the canonical example and their content type

WEB CLIENTS

Table 2.2.Resources referred to in the canonical example and their content type

WebProtocolsandPractice


Web clients

WEB CLIENTS

Foo1.gif

Foo2.gif

Foo3.jpg

Name:

Address:

:Credit Card

:Book Title

SUBMIT

Mp.tv

Book.cgi

Figure 2.2. Container document foo.html

WebProtocolsandPractice


Browser caching

WEB CLIENTS

Browser Caching

WebProtocolsandPractice


Browser caching1

WEB CLIENTS

Browser Caching

WebProtocolsandPractice


Issuing request by browser

WEB CLIENTS

Issuing Request By Browser

WebProtocolsandPractice


Browser configuration

WEB CLIENTS

Browser Configuration

WebProtocolsandPractice


Browser configuration1

WEB CLIENTS

Browser Configuration

WebProtocolsandPractice


Table 2 3 helper applications launched based on file content types

WEB CLIENTS

Table 2.3.Helper applications launched based on file/content types

WebProtocolsandPractice


Web clients

Browser

WEB CLIENTS

Foo.ra

Origin server

1 HTTP request for foo.ra

2 (Location, protocol)

3 Audio protocol request

Media server

Audio client

Figure 2.3. Listening to audio data

WebProtocolsandPractice


Web clients

Figure 2.3: The user selects a resource http://www.bar.com/foo.ra, and the browser sends an HTTP request to the origin server www.bar.com for the resource foo.ca (step 1). The origin server sends back an HTTP response (step 2), but the content of the response is simply a pointer to the information. The response is meaningful only to an audio client rather than a Web browser. Typically, the response is a URL such as pnm://ra-ms.com/foo.ra, where pnm stands for "Progressive Network Media" and ra-ms is the media server on which the resource foo.ca resides. Because the browser has been configured to invoke the helper program based on the file type, it would invoke the real-audio client program, which would contact the media server ra-ms.com (step 3) and start downloading the audio content.


Browser configuration2

WEB CLIENTS

Browser Configuration

WebProtocolsandPractice


Cookies

WEB CLIENTS

Cookies

WebProtocolsandPractice


Cookies1

WEB CLIENTS

Cookies

WebProtocolsandPractice


Web clients

WEB CLIENTS

Origin

Server A

Client

Request

Client

Response

Origin

Server A

Set-Cookie: XYZ

Origin

Server A

Client

Request

Cookie: XYZ

Figure 2.4. Client-server exchange of cookie information

WebProtocolsandPractice


Web clients

Figure 2.4 shows a client sending a request to an origin server (step 1). The origin server in its response includes the header (Set-cookie) with the cookie value (XYZ) (step 2). In all future requests to the origin server A, the client includes the cookie (step3, sent with the request via the header cookie).


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