Homework 4: Writing a Web server, part 2
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Due Thursday, Sep 25th, at 12:40pm (class start).


Homework grading comments
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Your code, as checked into svn, must parse and run as described below!
No partial credit will be given to programs that simply don't run
because of a typo or indentation error.

Section 0: Cleanup
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Deal with my comments on the third homework: fix problems, etc. (Be sure
to check for ``@CTB`` text throughout the file even if you
didn't lose any points!)

Section 1: Handle query strings
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Extend your Web server from HW #3 to properly parse the URLs and query
strings in GET requests. You should use the urlsplit function from the
urllib library module to extract the parameters from the URL:

    http://docs.python.org/lib/module-urlparse.html

and you should use the parse_qs function from the cgi library module to
parse the query string:

    http://docs.python.org/lib/node562.html#l2h-3818

The page returned by the Web server should contain, at a minimum,

        * the URL.
        * the text 'key=KEY; value=VALUE;' for each key/value pair in
          the GET request, with KEY and VALUE replaced by the actual key
          and value text.

So, for example, if the Web server is accessed at ::

  http://localhost:<port>/some/random/url?name=test&name=test2&blah=foo

then the returned page content should be something like ::

  hello, /some/random/url; key=name; value=test; key=name; value=test2;
  name=blah; value=foo

Spacing is important, here; e.g. please be sure to put ``' '`` after each ';'.

The returned status code should be 200 and the returned content-type
should be text/html.

The HTTP server should also ignore any non-GET requests; it's ok to
leave the behavior undefined for non-GET requests (i.e. don't bother
putting in error-handling for them unless you want to).

Section 2: Write a threaded Web server
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Extend your Web server from section 1 to do threaded dispatch, that is,
the server main thread should accept a connection and then spawn a new
thread to handle each connection.

A few parameters and suggestions:

        * Use the 'threading' module to do threading, and the 'socket'
          module to handle network connections.
        * Make sure that your connection-handling code is as
          encapsulated as possible; only the code that calls 'accept'
          should call the threading module, and the code that processes
          each connection should know nothing about threading.
        * Be sure to catch and report exceptions /in the thread/ rather
          than letting them fall through.
        * Put everything in functions; don't have any top-level code
          other than your function/class definitions and a call to a
          'main()' function.
        * Don't use any global data and share no information (variables,
          objects, etc.) between connections.
        * Your sockets should be *blocking*, not non-blocking.

The Web server should be submitted via your Subversion server under the
directory homework4/ and be in a file named webserve -- *note*, there's
no '.py' extension on that file!

webserve must take exactly one parameter, the port number on which to
serve HTTP. So, from the top of your svn repository, ::

   python homework4/webserve 5000

must start the Web server on port 5000.