ITEC 325 2014spring ibarland

home—lects—hws
D2L—breeze (snow day)

lect03-http-overview
intro: web requests and responses

• When you visit a web page, what happens? Consider the following responses, and how the decision is made. What, do you guess, is an http requirement (to be http compliant), vs. implemented by everybody (but maybe not http requirement), vs. a standard policy used by many but not all, vs. something that is an uncommon policy (or, could be a site-specific policy).
  • A file: www.radford.edu/ibarland/Info/proofreader-marks.html
  • A directory: www.radford.edu/ibarland/Info/
  • Another directory: www.radford.edu/ibarland/
  • Yet another directory: www.amazon.com/gp/
  • No file specified: www.radford.edu/
  • 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 (navigate from nytimes.com: e.g. &pagewanted=2)
  • Something hairy 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 sn.im/bburg-roundabout?
  • A basic php page: hello-world.php
  • hello-world.html (same content, but saved with suffix “html”)

  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... (img tags!)  [Also: 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"
  • In .NET, URLs like .../AnnouncementAdmin/Create are following the format website/controller/action where the parts between the slashes are used to decide what class-files to invoke.
  • Q: are URLs case-sensitive?
  • What is the exact path of the file that gets looked up, when requesting www.radford.edu/ibarland/foo/bar.html? What about same file, on 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.

Strings in php

"hello" . 17

'hello'

"he'llo"
'he"llo'

$myName = "Ian"
"hello, $myName.\nBye."
'hello, $myName.\nBye'

strlen("hi\n")
strlen('hi\n')

home—lects—hws
D2L—breeze (snow day)

©2013, Ian Barland, Radford University Last modified 2014.Jan.29 (Wed)

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