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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 Methods 1 2 3 4 HTTP Message Headers

Every request sent by an HTTP client causes one (or more) responses to be returned by the server that receives it. As we saw in the topic describing the response message format, the first line of the response is a status line that contains a summary of the results of processing the request. The purpose of this line is to communicate quickly whether or not the request was successful, and why.

HTTP status lines contain both a numeric status code and a text reason phrase. The idea behind this was taken directly from earlier application layer protocols such as FTP, SMTP and NNTP. The reason for having both a number and a text string is that computers can more easily “understand” the results of a request by looking at a number, and can then quickly respond accordingly. Humans, on the other hand, find numbers cryptic and text descriptions easier to comprehend. (The topic on FTP reply codes discusses more completely the reasons why numeric reply codes are used in addition to descriptive text.)

HTTP Methods 1 2 3 4 HTTP Message Headers