Structure of HTTP Messages Web Engineering HTTP-message = Request | Response generic-message = start-line *message-header Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt CRLF [ message-body ] Universität Karlsruhe start-line = Request-Line | Status-Line Fakultät für Informatik message-header = field-name ":" [ field-value ] CRLF Institut für Telematik Wintersemester 1999/2000 Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 1 Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 3 General Header Fields general-header = Cache-Control | Connection | Date Web Engineering | Pragma | Transfer-Encoding | Upgrade | Via Chapter 2: Foundation - Identifiers and Protocols (cont.) Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 2 Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 4
Request Response Request = Request-Line Response = Status-Line *(general-header | request-header | entity-header ) CRLF *(general-header | response-header | entity-header ) CRLF [ message-body ] [ message-body ] Request-Line = Method SP Request-URI SP HTTP-Version CRLF Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF Method = "OPTIONS" 1xx: Informational - Request received, continuing process � | "GET" 2xx: Success - The action was successfully received, � understood,and accepted | "HEAD" 3xx: Redirection - Further action must be taken in order to � | "POST" complete the request | "PUT" 4xx: Client Error - The request contains bad syntax or cannot � | "DELETE" be fulfilled | "TRACE" 5xx: Server Error - The server failed to fulfill an apparently � | extension-method valid request Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 5 Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 7 Request Header Fields Response Status Codes (selection) Developers can Status-Code = "100" ; Continue | "101" ; Switching Protocols request-header = Accept define response | "200" ; OK | Accept-Charset | Accept-Encoding | Accept-Language codes. They | "201" ; Created | Authorization must fit within | "202" ; Accepted | "203" ; Non-Authoritative Information | From one of the | "204" ; No Content | Host classes and | "300" ; Multiple Choices | If-Modified-Since | If-Match | If-None-Match they are treated | "301" ; Moved Permanently | "400" ; Bad Request | If-Range | If-Unmodified-Since (if unknown) as | "401" ; Unauthorized | Max-Forwards X00 | "402" ; Payment Required | Proxy-Authorization | "403" ; Forbidden | "404" ; Not Found | Range | "405" ; Method Not Allowed | Referer | "500" ; Internal Server Error | User-Agent | "501" ; Not Implemented Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 6 Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 8
Response Header Felder HTTP/1.1, Request Methods I � GET response-header = Age � to requests a resource | Location | Proxy-Authenticate � HEAD | Public � to request the header of a resource | Retry-After � POST | Server | Vary � to submit a resource (e.g. parameters) | Warning � DELETE, PUT | WWW-Authenticate � file manipulation functions, similar to FTP � OPTIONS � to request information about the server and intermediary programs � TRACE � to request information about the route Prof. Dr. Dr. h.c. mult. GerhardKrüger, Albrecht Schmidt: Web Engineering, WS00/01 page 9 Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 11 Entity Header Fields HTTP/1.1, Request Methods II entity-header = Allow � safe methods = | Content-Base calls of these methods don‘t change data on the server = | Content-Encoding these methods do not have any side-effects | Content-Language � HEAD | Content-Length � GET (should be implemented this way!) | Content-Location | Content-MD5 Content-MD5 � idempotente Methods = | Content-Range a single call of these method has the same effect as Is not a security feature, it | Content-Type multiple calls to of these methods = | Etag is only a mechanism to side-effects of N > 0 identical requests is the same as for a | Expires track accidental change of single request. | Last-Modified the message body – � HEAD | extension-header because if the body can � PUT � DELETE be altered also the � GET (should be implemented this way!) Content-MD5 could be changed. Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 10 Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 12
Conditional GET HTTP/1.1, GET Request � Syntax: � Syntax: GET <URI> <VERSION> GET <URI> <VERSION> <CONDITIONAL-HEADER>: <DATE> � Request resource named by the URI z.B. If-Modified-Since, If-Match, If-Range, etc. � static resource � dynamic resource � Example: � providing parameters GET http://www.apache.org/index.html HTTP/1.1 Host: www.apache.org � conditional GET If-Modified-Since: Fri, 29 Oct 1999 13:53:40 GMT � get the resource only under a certain condition � may reduce network traffic HTTP/1.0 304 Not Modified � partial GET Date: Thu, 28 Oct 1999 13:55:13 GMT Content-Type: text/html � Get only a certain part of the resource Expires: Fri, 29 Oct 1999 13:55:13 GMT � may reduce network traffic Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 13 Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 15 HTTP/1.1, GET Example Partial GET � Syntax: GET /index.html HTTP/1.1 GET <URI> <VERSION> Accept: */* Range: <RANGE> Accept-Language: en-us z.B. bytes=0-499 get the first 500 bytes of the resource Accept-Encoding: gzip, deflate bytes=-100 get the last 100 bytes of the resource User-Agent: Mozilla/4.0 (compatible; MSIE5.0; Windows NT) bytes=1500- get the resource starting from byte 1500 Host: www.teco.edu Connection: Keep-Alive � Beispiel: GET /Default. htm HTTP/1.1 HTTP/1.1 200 OK Host: www.microsoft.com Range: bytes=0-80 Date: Wed, 27 Oct 1999 14:13:43 GMT Server: Apache/1.2.1 Keep-Alive: timeout=10, max=100 HTTP/1.1 206 Partial content Connection: Keep-Alive Server: Microsoft-IIS/4.0 Transfer-Encoding: chunked Date: Thu, 28 Oct 1999 14:21:00 GMT Content-Type: text/html Content-Type: text/html Content-Length: 81 Content-Range: bytes 0 -80/19618 f78 <html><head> <HTML><HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso88 <title>Telecooperation Office (TecO)</title> ... Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 14 Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 16
HTTP/1.1, HEAD Example II HTTP/1.1, HEAD Request GET / HTTP/1.0 Host: www.sun.com � Syntax: HEAD <URI> <VERSION> Accept: */* Accept-Language: en-us � request the header information of a resource User-Agent: Mozilla/4.0 (compatible; MSIE5.0; Windows NT) name by the URI HTTP/1.1 200 OK � serves the same header information as a GET Server: Netscape-Enterprise/3.6 request of the same resource Date: Fri, 03 Nov 2000 06:10:24 GMT Set-cookie: sessionid=TVOS0UYAAC00XAMTA1LU5YQ;path=/ � request of meta information Content-type: text/html Content-length: 13657 � used for Connection: close � checking links <!DOCTYPE HTML .... � checking whether or not it is required to transmit the <HTML... ... resource (e.g. compare time stamp or size) � may reduce network traffic GET serves the same headers as before HEAD Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 17 Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 19 HTTP/1.1, HEAD Example I HTTP/1.1, POST Request HEAD / HTTP/1.0 � Syntax: Host: www.sun.com POST <URI> <VERSION> Accept: */* Accept-Language: en-us <HEADER> User-Agent: Mozilla/4.0 (compatible; MSIE5.0; Windows NT) <CRLF> HTTP/1.1 200 OK <MESSAGE-BODY> Server: Netscape-Enterprise/3.6 Date: Fri, 03 Nov 2000 06:10:24 GMT Set-cookie: sessionid=TVOS0UYAAC00XAMTA1LU5YQ;path=/ � Supply data to a resource named in the URI Content-type: text/html Content-length: 13657 (see chapter on programming) Connection: close � return codes: � 200 OK � 204 No Content � 201 Created (location header) Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 18 Prof. Dr. Dr. h.c. mult. Gerhard Krüger , Albrecht Schmidt: Web Engineering, WS00/01 page 20
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