This lesson is going to review things that we have already talked about, since week 11, but stitching them together in a way that will be a bit more clear and directly applicable to the work you will be doing for your final project.
Step 1. week14_inclass1.pyde
Look at what the URL looks like when submit the Mad Lib form. It looks something like this:
http://127.0.0.1:8000/cgi-bin/server.py?name=Gritty&species=monster
All the text in blue is called a query
string. It comprises a list of key-value
pairs that the client sends to the server. We can use
this same format whether it is a web browser submitting an HTML
form or a Processing program making a network
request. The query string is comprised of one
or more parameters, very similar to
the parameters or arguments
that you pass to a function when you invoke a Python or
Processing command, but the syntax is quite different.
In this case, each parameter is separated by an
ampersand (&). The key is
specified by name, then an equal sign, then
the value. So the above reqest is sending
two key-value pairs to the server:
name which equals Gritty, and
species which equals monster.
Step 2. This code adds a unique ID that we will
submit with our data so the server can save the data for each
client uniquely. It also adds a new tab
called network. For now, this will implement a
function that will make the network send that data to the
server. That tab includes a variable
called lastSend that it uses to limit (or
"throttle") requests to once per second. You
can adjust the timing here to experiment with the timing and
interaction of your own project — but be mindful that
the framerate of a Processing sketch (probably
30-60 frames per second) is much faster than you would probably
want to make requests over a network, unless you were working
with a more specialized protocol that was designed to handle
many more requests.
week14_inclass2.pyde
network tab
Step 3.
In this last step, the network tab includes additional code to
receive a response from the server in the form of JSON. It
parses that response, and returns it so that you can loop over
that data in draw() to render that data on the
screen.
week14_inclass3.pyde
network tab
The server code for this is included
here: server.py. Remember to
put this in a subfolder called cgi-bin within your
project folder, and to adjust the permissions to that it is
executable (see week 11 for this) and
you can run it by running the built-in Python CGI web server
(also see week 11).