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Appendix B HyperText Transfer Protocol
This appendix provides a short introduction to a few HyperText Transfer Protocol (HTTP) basics. For more information on HTTP, see the Internet Engineering Task Force (IETF) home page at:
This appendix contains the following sections:
About HyperText Transfer Protocol (HTTP)
The HyperText Transfer Protocol (HTTP) is a protocol (a set of rules that describe how information is exchanged on a network) that allows a web browser and a web server to "talk" to each other using the ISO Latin1 alphabet, which is ASCII with extensions for European languages.
HTTP is based on a request/response model. The client connects to the server and sends a request to the server. The request contains the following: request method, URI, and protocol version. The client then sends some header information. The server's response includes the return of the protocol version, status code, followed by a header that contains server information, and then the requested data. The connection is then closed.
The iPlanet Web Server 4.x supports HTTP 1.1. Previous versions of the server supported HTTP 1.0. The server is conditionally compliant with the HTTP 1.1 proposed standard, as approved by the Internet Engineering Steering Group (IESG) and the Internet Engineering Task Force (IETF) HTTP working group. For more information on the criteria for being conditionally compliant, see the Hypertext Transfer ProtocolHTTP/1.1 specification (RFC 2068) at:
A request from a client to a server includes the following information:
A client can request information using a number of methods. The commonly used methods include the following:
GETRequests the specified document
The client can send header fields to the server. Most are optional. Some commonly used request headers are shown in Table B-1.
If the client has made a POST or PUT request, it can send data after the request header and a blank line. If the client sends a GET or HEAD request, there is no data to send; the client waits for the server's response.
The server's response includes the following:
When a client makes a request, one item the server sends back is a status code, which is a three-digit numeric code. There are four categories of status codes:
Status codes in the 100-199 range indicate a provisional response.Table B-2 contains some common status codes.
Use a local copy. If a browser already has a page in its cache, and the page is requested again, some browsers (such as Netscape Navigator) relay to the web server the "last-modified" timestamp on the browser's cached copy. If the copy on the server is not newer than the browser's copy, the server returns a 304 code instead of returning the page, reducing unnecessary network traffic. This is not an error.
The response header contains information about the server and information about the document that will follow. Common response headers are shown in Table B-3.
The server sends a blank line after the last header field. The server then sends the document data.
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Copyright © 2001 Sun Microsystems, Inc. Some preexisting portions Copyright © 2001 Netscape Communications Corp. All rights reserved.
Last Updated May 09, 2002