Homework 4: Writing a Web server, part 2

Due Thursday, Sep 25th, at 12:40pm (class start).

Homework grading comments

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

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

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

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.