Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Enjoy The TCP/IP Guide? Get the complete PDF!
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
                9  TCP/IP World Wide Web (WWW, "The Web") and the Hypertext Transfer Protocol (HTTP)
                     9  TCP/IP Hypertext Transfer Protocol (HTTP)
                          9  HTTP General Operation and Connections

Previous Topic/Section
HTTP General Operation and Connections
Previous Page
Pages in Current Topic/Section
1
23
Next Page
HTTP Transitory and Persistent Connections and Pipelining
Next Topic/Section

HTTP Operational Model and Client/Server Communication
(Page 1 of 3)

The Hypertext Transfer Protocol is the application-layer protocol that implements the World Wide Web. While the Web itself has many different facets, HTTP is only concerned with one basic function: the transfer of hypertext documents and other files from Web servers to Web clients. In terms of actual communication, clients are chiefly concerned with making requests to servers, which respond to those requests.

Thus, even though HTTP includes a lot of functionality to meet the needs of clients and servers, when you boil it down, what see is a very simple, client/server, request/response protocol. In this respect, HTTP more closely resembles a rudimentary protocol like BOOTP or ARP than it does other application-layer protocols like FTP and SMTP, which all involve multiple communication steps and command/reply sequences.

Basic HTTP Client/Server Communication

In its simplest form, the operation of HTTP involves only an HTTP client, usually a Web browser on a client machine, and an HTTP server, more commonly known as a Web server. After a TCP connection is created, the two steps in communication are as follows:

  1. Client Request: The HTTP client sends a request message formatted according to the rules of the HTTP standard—an HTTP Request. This message specifies the resource that the client wishes to retrieve, or includes information to be provided to the server.

  2. Server Response: The server reads and interprets the request. It takes action relevant to the request and creates an HTTP Response message, which it sends back to the client. The response message indicates whether the request was successful, and may also contain the content of the resource that the client requested, if appropriate.

    Figure 315: HTTP Client/Server Communication

    In its simplest form, HTTP communication consists of an HTTP Request message sent by a client to a server, which replies with an HTTP Response.

     


In HTTP/1.0, each TCP connection involves only one such exchange, as shown in Figure 315; in HTTP/1.1, multiple exchanges are possible, as we'll see in the next topic. Note also that the server may in some cases respond with one or preliminary responses prior to sending the full response. This may occur if the server sends a preliminary response using the “100 Continue” status code prior to the “real” reply. See the topic on HTTP status codes for more information.

Key Concept: HTTP is a client/server-oriented, request/reply protocol. Basic communication consists of an HTTP Request message sent by an HTTP client to an HTTP server, which returns an HTTP Response message back to the client.



Previous Topic/Section
HTTP General Operation and Connections
Previous Page
Pages in Current Topic/Section
1
23
Next Page
HTTP Transitory and Persistent Connections and Pipelining
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.