SDSU CS 580 Client-Server Programming
Fall Semester, 2002
HTTP & XML-RPC
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© 2002, All Rights Reserved, SDSU & Roger Whitney
San Diego State University -- This page last updated 08-Oct-02

Contents of Doc 13, HTTP & XML-RPC


References

Hypertext Transfer Protocol - HTTP/1.0, Berners-Lee, Fielding, Nielson, rfc1945, http://www.w3.org/Protocols/rfc1945/rfc1945

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

Uniform Resource Identifiers (URI): Generic Syntax, Berners-Lee, Fielding, Masinter, rfc2396 http://www.ietf.org/rfc/rfc2396.txt

XML-RPC Specification, http://www.xmlrpc.com/spec

Reading

HTTP/1.0 rfc1945 

Doc 13, HTTP & XML-RPC Slide # 2

Client-Server Protocols


Client-Server Protocol defines



Must define protocol before building client & server


Too learn about protocols we will look at several examples

Starting with HTTP 

Doc 13, HTTP & XML-RPC Slide # 3

URI


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 13, HTTP & XML-RPC Slide # 4

HTML

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 13, HTTP & XML-RPC Slide # 5
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 is content sent by HTTP 

<HTML>
<HEAD>
<TITLE>Sample HTML Document</TITLE>
</HEAD>
<BODY>
This is a document
</BODY>
</HTML>

Doc 13, HTTP & XML-RPC Slide # 6

HTTP



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 13, HTTP & XML-RPC Slide # 7

HTTP Message Format 


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 13, HTTP & XML-RPC Slide # 8

Client Request 


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 13, HTTP & XML-RPC Slide # 9

Full-Request


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 13, HTTP & XML-RPC 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 13, HTTP & XML-RPC Slide # 11

Server Response


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 13, HTTP & XML-RPC 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 13, HTTP & XML-RPC 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 

Doc 13, HTTP & XML-RPC Slide # 14
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


Cookies were added to HTTP by adding a new name-value pair

Clients/servers that were not programmed for cookies ignored the new name-value pair 

Doc 13, HTTP & XML-RPC Slide # 15
Name -Value Pairs are Everywhere

Data Files
Which is easier for a program to parse?Which is safer 

Allen, Sally

87

92

85

55

74

10

Battista, Joe

92

98

98

55

78

10

Biag, Sam

83

91

78

51

72

8

Chen, Pete

89

92

89

57

79

10

Chen, Roger

74

68

59

61

55

10


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

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 13, HTTP & XML-RPC Slide # 16
Name-Value Pairs and Parameters

Most languages use positional matching for parameters 

“The cat in the hat came back”.substring( 2, 6);


Smallktalk uses name-value pairs 

 ‘The cat in the hat came back’ copyFrom: 2 to: 6

copyFrom:to: is on method

Keyword (name)
Parameter (value)
copyFrom:
 2
to:
 6
 

Doc 13, HTTP & XML-RPC Slide # 17
Name -Value Pairs are Your Friends

Don't program without them 

Doc 13, HTTP & XML-RPC Slide # 18
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 13, HTTP & XML-RPC Slide # 19

Request Methods 


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 13, HTTP & XML-RPC Slide # 20
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 13, HTTP & XML-RPC Slide # 21
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 
Doc 13, HTTP & XML-RPC Slide # 22

XML-RPC

Requests

Send via HTTP post

User-Agent & Host must be specified

Content-Type is text/xml

Content-Length must be specifed and be correct in bytes

Content is in XML and contains single <methodCall>

Example 

POST /cs580 HTTP/1.1
Host: rugby.sdsu.edu:8008
Content-length: 158
Content-type: text/xml;charset=iso-8859-1
User-Agent: Smalltalk XMLRPC version 0.5 (VisualWorksÆ NonCommercial, Release 7 of June 14, 2002)
Connection: keep-alive
 
<?xml version="1.0"?><methodCall><methodName>officeDataFor</methodName><params>
   <param><value><string>Whitney</string></value></param>
</params></methodCall>


Doc 13, HTTP & XML-RPC Slide # 23
XML in Requests 

<methodCall>
   <methodName>[Character]*</methodName>
   <params>
      <param><value>[Legal type]</value></param>*
   </params>
</methodCall>

Characters – string of characters

Legal types 

<i4> or <int>
<boolean>
<string>
<double>
<dateTime.iso86021>
<base64>



<struct>
   <member>
      <name>[Character]*</name>
      <value>[Legal type]</value>
   </member>*
</struct>
<array>
   <data>
      <value>[Legal type]</value>
   </data>*
</array>


Doc 13, HTTP & XML-RPC Slide # 24
Response

Unless lower-level error always return 200 OK

Content type is text/xml

Content-length must be present and be correct

Body contains on XML structure <methodResponse>

Example 

HTTP/1.0 200 OK
Date: Tue, 8 Oct 2002 23:27:43 -0700
Server: VisualWave TinyHTTP/1.0
Mime-version: 1.0
Content-type: text/xml;
Content-length: 252
   
<?xml version="1.0"?><methodResponse><params><param><value><array><data>
   <value><string>Whitney</string></value>
   <value><string>P-243</string></value>
   <value><string>594-3535</string></value>
</data></array></value></param></params></methodResponse>

Doc 13, HTTP & XML-RPC Slide # 25
Response XML

Response contains one <methodReponse> tag

The <methodReponse> tag can contain either

<params> tag can only contain one <param>

methodReponse Structure 

<?xml version="1.0"?>
<methodResponse>
   <params>
      <param>
         <value>[Legal type]</value>
      </param>
   </params>
</methodResponse>


<?xml version="1.0"?>
<methodResponse>
   <fault>
      <value>[Legal type]</value>
   </fault>
</methodResponse>


Copyright ©, All rights reserved.
2002 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.
OpenContent license defines the copyright on this document.
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