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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 Messages, Message Formats, Methods and Status Codes

HTTP Request Message Format 1 2 3 HTTP Methods

Up and down; east and west; black and white; yin and yang. Well, you get the idea. Each request message sent by an HTTP client to a server prompts the server to send back a response message. Actually, in certain cases the server may in fact send two responses, a preliminary response followed by the real one. Usually though, one request yields one response, which indicates the results of the server's processing of the request, and often also carries an entity (file or resource) in the message body.

Like requests, responses use their own specific message format that is based on the HTTP generic message format. The format, shown in Figure 318, is:

<status-line>
<general-headers>
<response-headers>
<entity-headers>
<empty-line>
[<message-body>]
[<message-trailers>]

Figure 318: HTTP Response Message Format

This figure illustrates the construction of an HTTP response, and includes an example of both message headers and body. The status code “200” indicates that this is a successful response to a request; it contains a brief text HTML entity in the message body. See Figure 317 for the HTTP request format.

HTTP Request Message Format 1 2 3 HTTP Methods

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