ITEC 325 2015spring ibarland

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intro
intro: web requests and responses

• When you visit a web page, what happens?
  • A file: www.radford.edu/ibarland/Info/proofreader-marks.html
  • A directory: www.radford.edu/ibarland/Info/
  • Another directory: http://www.radford.edu/ibarland/
  • Yet another directory: www.nytimes.com/2013/01/
  • File doesn't exist:www.homestarrunner.com/asdfasdfasdf
    (Btw, here's a 5-min TED talk on how a business can learn from rethinking its 404 page experience. The first 3min are annoying, but the final lesson is sound.)
  • A page with GET params: e.g. www.nytimes.com/2010/11/14/magazine/14Hacker-t.html, pulling up later pages, and using “pagewanted=all”.
  • Some hairy URL like maps.google.com/?ll=37.235094,-80.420677&spn=0.000536,0.000916&hnear=1600+N+Main+St,+Blacksburg,+Virginia+24060&t=h&z=20&vpsrc=6
  • What about tinyurl.com/7efr7fy — what is happening here?
  • An amazon item. What if we change the case of “amazon.com”? What if we change the case of the remainder of the URL? Say, this simple group card-game, and then we change some text...
  • A basic php page: hello-world.php
  • hello-world-php.txt (same content, but saved with suffix “txt”)

  For this class, I recommend Chrome, or Firefox w/ Firebug. We will not try to support IE!

          Client                             Server
  
          Browser            ->request->
                              (URL)
                                             WebServer (Apache)
                                               - look up file:
                                               - possibly redirect...
                                               - what if file exists, but no permissions?
                                               - what if file doesn't exist?
                                               - what if URL is a directory?
                                               - what if request from a mobile platform?
                                               - process any php (as configured)
                                                 which may invoke other programs, db connections, etc
                              <-response<-
                              (html, jpg,
                               html+javascript,
                               ...)
          
         Browser
          ...makes a gui window,
             lays out text/color/pictures
             Displays response
          Also:
          ...makes add'l URL requests... [Ad blocker!]
          ...runs javascript...
          ...invokes plug-ins or passes to OS...
  
          
          
          
          HTTP response codes
  
  
  What happens for each of:
  - starting up at Starbucks, when you get 'welcome to our wireless; please agree to our terms'.
  - telling my phone to use RUWireless, even not in browser a page comes up w/ "please authenticate"
  - Q: are URLs case-sensitive?
  - what is the file that gets looked up, by the www.radford.edu web server?  By php.radford.edu ?
  - sites that pop up 20 other windows (usually adverts)?  Whose fault is that?
  - Referring page is often given ... Shriram's security leak.
  
  
  
  
  
         
  
  
   
          
          
  
  
          
  

• Running php from the command line.
  To run interactively: php -a

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©2014, Ian Barland, Radford University Last modified 2015.Jan.23 (Fri)

Please mail any suggestions (incl. typos, broken links) to ibarlandradford.edu