• HTTP
  • A protocol for distributed, collaborative, hypermedia information systems.
  • A request/response standard typical of client-server computing.
  • Currently dominant version is HTTP/1.1.
• Massively used to deliver content over the Web
  • Web browsers and spiders are relying on HTTP.
• The protocol is not constrained to TPC/IP
  • It only presumes a reliable transport.
• Resources accessed by HTTP are identified by URIs (more specifically URLs), using the http URI schemes. 
  

• Request consists of
  • Request line, such as GET /images/logo.gif HTTP/1.1, which requests are source called /images/logo.gif from server.
  • Headers, such as Accept-Language: en
  • An empty line
  • An optional message body
• Response consists of
  • Status line which includes numeric status code and textual reason phrase
  • Response headers
  • An empty line
  • The requested content
    

• HTTP request methods indicate the desired action to be performed on the identified resource:           
  • GET
    • Requests a representation of the specified resource. GET should not be used for operations that cause side-effects (problematic with robots and crawlers). Those operations are called safe operations.
  • POST
    • Submits data to be processed (e.g., from an HTML form) to the identified resource. The data is included in the body of the request.
  • PUT
    • Uploads a representation of the specified resource.
  • DELETE
    • Deletes the specified resource.

• Example is relying on curl which is a command line tool used to transfer data with URL syntax
  • Supports many protocols such as FTP, FTPS, HTTP, HTTPS, SCP, SFTP, etc.
  • More information can be found at http://curl.haxx.se
• curl usage pattern is simple:
  
  $ curl -v http://www.google.at
  * About to connect() to www.google.at port 80 (#0)
  * Trying 74.125.87.104... connected
  * Connected to www.google.at (74.125.87.104) port 80 (#0)
  > GET / HTTP/1.1
  > User-Agent: curl/7.19.6 (i686-pc-cygwin) libcurl/7.19.6 OpenSSL/0.9.8o zlib/1.2.3 libidn/1.18 libssh2/1.2
  > Host: www.google.at
  > Accept: */*
  >
  < HTTP/1.1 200 OK
  < Date: Sun, 13 Jun 2010 15:13:15 GMT
  < Expires: -1
  < Cache-Control: private, max-age=0
  < Content-Type: text/html; charset=ISO-8859-1
  < Set-Cookie: PREF=ID=29937d127162f98f:TM=1276441995:LM=1276441995:S=wQcvUApkDnuGPQEa; expires=Tue, 12-Jun-2012 15:13:15
  < Server: gws
  < X-XSS-Protection: 1; mode=block
  < Transfer-Encoding: chunked
  <
  …

Srdjans-MacBook-Pro:~ skomazec$ curl -v http://www.sti-innsbruck.at/fileadmin/scripts/foaf.php?id=215

* About to connect() to www.sti-innsbruck.at port 80 (#0)

* Trying 138.232.65.141... connected* Connected to www.sti-innsbruck.at (138.232.65.141) port 80 (#0)

> GET /fileadmin/scripts/foaf.php?id=215 HTTP/1.1

> User-Agent: curl/7.19.7 (universal-apple-darwin10.0) libcurl/7.19.7 OpenSSL/0.9.8l zlib/1.2.3

> Host: www.sti-innsbruck.at

> Accept: */*

> 

< HTTP/1.1 200 OK

< Date: Sun, 06 Jun 2010 15:55:57 GMT

< Server: Apache

< X-Powered-By: PHP/5.2.0-8+etch16

< Content-Length: 944

< Content-Type: text/html; charset=UTF-8

< 

xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"

xmlns:foaf="http://xmlns.com/foaf/0.1/">

Srdjan Komazec

Srdjan

Komazec

7348d8f19c568de04c7718880f700fad7acdfab9

* Connection #0 to host www.sti-innsbruck.at left intact

* Closing connection #0

Requested resource