URI

HTML

HTTP

HTTP Message Format

Contents of Doc 6, HTTP

Client Request

Full-Request

Server Response

Request Methods

	CS 580 Client-Server Programming Fall Semester, 2000 HTTP
	Previous Lecture Notes Index Next © 2000, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 05-Sep-00

References
Hypertext Transfer Protocol - HTTP/1.0, Berners-Lee, Fielding, Nielson, http://info.internet.isi.edu:80/in-notes/rfc/files/rfc1945.txt

Hypertext Transfer Protocol -- HTTP/1.1, Fielding, Gettys, Mogul, Masinter, Leach, Berners-Lee, http://www.w3.org/Protocols/rfc2616/rfc2616.txt

Uniform Resource Identifiers (URI): Generic Syntax, Berners-Lee, Fielding, Masinter, http://info.internet.isi.edu:80/in-notes/rfc/files/rfc2396.txt

Reading
HTTP/1.0 rfc1945


Doc 6, HTTP Slide # 2

URI = Uniform Resource Identifiers
URL = Uniform Resource Locator

gopher://gopher.yoyodyne.com/
news:rec.gardening
http://www.yoyodyne.com/pub/foobar.html
http://www.yoyodyne.com/pub/foobar.html?roger

Common Internet Scheme Syntax

URL schemes that involve the direct use of an IP-based protocol to a specified host on the Internet use a common syntax for the scheme-specific data:

//<user>:<password>@<host>:<port>/<url-path>


Doc 6, HTTP Slide # 3

Some Buzz Words
WWW

World Wide Web (or Web, for short)

SGML

Standard Generalized Markup Language
this is a standard for describing markup languages

DTD

Document Type Definition
this is a specific markup language, written using SGML

HTML

HyperText Markup Language
HTML is a SGML DTD.
HTML uses markup tags to tell the Web browser how to display the text

XML

Extensible Markup Language

XHTML

XML + HTML 4.0


Doc 6, HTTP Slide # 4

What is HTML?
HTML is a language for describing structured documents

HTML does not describe page layout

Web browsers use HTML to render & display a document

HTML versions

HTML 1.0: very limited
HTML 2.0: addition of forms (rfc1866.txt)
HTML 3.0: failed attempt at standardization
HTML 3.2: prime candidate for standard. http://www.w3.org/TR/REC-html32:
HTML 4.0: http://www.w3.org/TR/REC-html40

style sheets	scripting
frames	embedding objects
richer tables	enhancements to forms

Other developments:

CSS (Cascading Style Sheets)

XML (Extensible Stylesheet Language)

Used to transform XML documents


Doc 6, HTTP Slide # 5

Basic HTML Document

<HTML>
<HEAD>
<TITLE>Sample HTML Document</TITLE>
</HEAD>
<BODY>
This is a document
</BODY>
</HTML>
Doc 6, HTTP Slide # 6

Stateless (http 1.0)
Object-oriented protocol

The typing and negotiation of data representation, allows systems to be built independently of the data being transferred

Assigned port 80

Basic Server-Client Interaction (http 1.0)
Client: Open connection

Server: Accept/Reject connection

Client: Send request

Server: Send response to request

Connection closed


Doc 6, HTTP Slide # 7

HTTP-message   =   Simple-Request       (HTTP/0.9 messages)
   | Simple-Response
   | Full-Request               (HTTP/1.0 messages)
   | Full-Response
Full-Request   =   Request-Line 
   *( General-Header   | Request-Header  | Entity-Header ) 
   CRLF
   [ Entity-Body ]
Full-Response  =    Status-Line      
   *( General-Header   | Request-Header   | Entity-Header ) 
   CRLF
   [ Entity-Body ]
HTTP-header   = field-name ":" [ field-value ] CRLF
Entity-Body   = *OCTET


Doc 6, HTTP Slide # 8

Request    = Simple-Request | Full-Request
Simple-Request = "GET" SP Request-URI CRLF

Simple-Request Example

rohan 11-> telnet www.eli.sdsu.edu 80
Trying 130.191.226.80...
Connected to www.eli.sdsu.edu.
Escape character is '^]'.
GET /courses/fall00/cs580/index.html
<HTML>
<HEAD>
<TITLE>CS 580: Course Web Site</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<TABLE BORDER=0 WIDTH="100%">
...stuff removed...
</sub>Visitors since 21-Aug-00
</center>
</BODY>
</HTML>
Connection closed by foreign host.


Doc 6, HTTP Slide # 9

Full-Request   =   Request-Line 
   *( General-Header   | Request-Header   | Entity-Header ) 
   CRLF
   [ Entity-Body ]

Request-Line   = Method SP URI SP HTTP-Version CRLF

rohan 13-> telnet www.eli.sdsu.edu 80
Trying 130.191.226.80...
Connected to www.eli.sdsu.edu.
Escape character is '^]'.
GET /courses/fall00/cs580/index.html HTTP/1.0
HTTP/1.1 200 OK
Date: Tue, 05 Sep 2000 19:31:14 GMT
Server: Apache/1.3.9 (Unix) PHP/3.0.12
Last-Modified: Mon, 04 Sep 2000 21:03:56 GMT
ETag: "14c199-7e8-39b40e3c"
Accept-Ranges: bytes
Content-Length: 2024
Connection: close
Content-Type: text/html
X-Pad: avoid browser bug
<HTML>
<HEAD>
<TITLE>CS 580: Course Web Site</TITLE>
</HTML>
... stuff removed here...
Connection closed by foreign host.

Note 2 CRLF are needed to end the full request


Doc 6, HTTP Slide # 10

HTTP 1.1 Example

rohan 14-> telnet www.eli.sdsu.edu 80
Trying 130.191.226.80...
Connected to www.eli.sdsu.edu.
Escape character is '^]'.
GET /courses/fall00/cs580/index.html HTTP/1.1
Connection: close
Host: www.eli.sdsu.edu
HTTP/1.1 200 OK
Date: Tue, 05 Sep 2000 22:41:26 GMT
Server: Apache/1.3.9 (Unix) PHP/3.0.12
Last-Modified: Mon, 04 Sep 2000 21:03:56 GMT
ETag: "14c199-7e8-39b40e3c"
Accept-Ranges: bytes
Content-Length: 2024
Connection: close
Content-Type: text/html
X-Pad: avoid browser bug
<HTML>
<HEAD>
<TITLE>CS 580: Course Web Site</TITLE>
</HEAD>
...stuff removed here...
</BODY>
</HTML>
Connection closed by foreign host.


Doc 6, HTTP Slide # 11

Example Full-response

HTTP/1.0 200 Document follows
MIME-Version: 1.0
Server: CERN/3.0
Date: Thursday, 21-Mar-96 17:00:45 GMT
Content-Type: text/html
Content-Length: 2686
Last-Modified: Tuesday, 27-Feb-96 05:34:12 GMT

field-name

field-value

MIME-Version:

1.0

Server:

CERN/3.0

Date:

Thursday, 21-Mar-96 17:00:45 GMT

Content-Type:

text/html

Content-Length:

2686

Last-Modified:

Tuesday, 27-Feb-96 05:34:12 GMT


Doc 6, HTTP Slide # 12

What is the big Deal?

What are the data fields in this?

1.0; CERN/3.0; Thursday, 21-Mar-96 17:00:45 GMT; text/html; 2686; Tuesday, 27-Feb-96 05:34:12 GMT

What are the data fields in this?

MIME-Version: 1.0
Server: CERN/3.0
Date: Thursday, 21-Mar-96 17:00:45 GMT
Content-Type: text/html
Content-Length: 2686
Last-Modified: Tuesday, 27-Feb-96 05:34:12 GMT

Which is Safer?
Which is Easier to Parse?


Doc 6, HTTP Slide # 13

Name -Value Pairs are GoodDoes Order Matter?

MIME-Version: 1.0
Server: CERN/3.0
Date: Thursday, 21-Mar-96 17:00:45 GMT
Content-Type: text/html
Content-Length: 2686
Last-Modified: Tuesday, 27-Feb-96 05:34:12 GMT

Server: CERN/3.0
Content-Type: text/html
MIME-Version: 1.0
Content-Length: 2686
Last-Modified: Tuesday, 27-Feb-96 05:34:12 GMT
Date: Thursday, 21-Mar-96 17:00:45 GMT

Extending Protocols

MIME-Version: 1.0
Server: CERN/3.0
Date: Thursday, 21-Mar-96 17:00:45 GMT
Content-Type: text/html
Forwarded: by http://rohan.sdsu.edu/ for cs.sdsu.edu
Content-Length: 2686
WhitneyInfo: Hi Mom
Last-Modified: Tuesday, 27-Feb-96 05:34:12 GMT


Doc 6, HTTP Slide # 14

Name -Value Pairs are Everywhere
Data Files Which is easier for a program to parse?Which is safer

name

course

hwork

exam1

exam2

final

as1

Allen, Sally

Battista, Joe

Biag, Sam

Chen, Pete

Chen, Roger

lastName:Allen, lastName:Sally, course:87, hwork:92, exam1:85, exam2:55, final:74, as1:10
lastName:Battista, lastName:Joe, course:92, hwork:98, exam1:98, exam2:55, final:78, as1:10
lastName:Baig, lastName:Sam, course:83, hwork:91, exam1:78, exam2:51, final:72, as1:8
lastName:Chen, lastName:Pete, course:89, hwork:92, exam1:89, exam2:57, final:79, as1:10
lastName:Chen, lastName:Roger, course:74, hwork:68, exam1:59, exam2:61, final:55, as1:10


Doc 6, HTTP Slide # 15

Name -Value Pairs are Your Friends
Don't program without them


Doc 6, HTTP Slide # 16

Big Issue: In-line data
If we send binary data or data of unknown format how does receiver know when the data ends?

POP solution
Use termination sequence

Insure that termination sequence does not occur in data

HTTP Solution

Full-Response  = Status-Line
   *General-Header         
   *Response-Header      
   *Entity-Header      
   CRLF
   [ Entity-Body ]

Send length of data to be sent in header


Doc 6, HTTP Slide # 17

Allen, Sally

Battista, Joe

Chen, Pete

Chen, Roger

Method         = "GET" | "HEAD" | "PUT" | "POST"
   | "DELETE" | "LINK" | "UNLINK"
   | extension-method

All HTTP/1.0 servers must support GET and HEAD

Servers should return the Status-Code

"501 Not Implemented"

if the method is unknown.

GET
Retrieves whatever item is identified by the URI.

The URI can refer to a data-producing process, or a script

The produced data which shall be returned as the Entity-Body

HEAD
Identical to GET except that the server must not return any Entity-Body in the response


Doc 6, HTTP Slide # 18

POST

Request that the origin server accept the item enclosed in the request as a new subordinate of the resource identified by the URI

Allows a uniform function to:

Annotation of existing documents;
Posting a message to a bulletin board topic, newsgroup, mailing list, or similar group of articles;
Providing a block of data (usually a form) to a data-handling process, or a script, which can be run by such a process;
Extending a document during authorship


Doc 6, HTTP Slide # 19

These are not always supported
Why?

PUT
The enclosed item in the request is to be stored under the supplied URI
DELETE
Requests that the server delete the resource identified by the given URI

LINK
Establishes one or more Link relationships between the existing resource identified by the URI and other existing resources

UNLINK
UNLINK method removes one or more Link relationships from the existing resource identified by the URI

Copyright ©, All rights reserved.
2000 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.
OpenContent license defines the copyright on this document.

Previous visitors since 05-Sep-00 Next