Learning Processing: A Beginner's Guide to Programming Images ...

372 Learning Processing
If you are working on a multi-user project, you most
likely want to run the servers and clients on separate
computers. After all, this is the point of creating multiuser
applications in the fi rst place. However, for testing
and development purposes, it is often convenient to run
all the elements from one computer. In this case, the
server IP address will be “ localhost ” or 127.0.0.1 (note
this is the IP address used in this chapter’s examples).
As will be covered in Section 21.3, Processing ’s “ export to
application ” feature will allow you to export a stand-alone
application for your server, which you can then run in the
background while you develop your client in Processing .
Details as to how “ export to application ” works can be
found in Chapter 18. You can also run multiple copies
of a stand-alone application to simulate an environment
with more than one client. Figure 19.6 shows the server
running with two client instances.
19.8
Exercise 19-4: Expand the whiteboard to allow for color. Each client should send a red,
green, and blue value in addition to the XY location. You will not need to make any changes
to the server for this to work.
Exercise 19-5: Create a two-player game of Pong played over the network. Th is is a complex
assignment, so build it up slowly. For instance, you should get Pong to work fi rst without
networking (if you are stuck, an example is provided at the book’s web site). You will also
need to make changes to the server; specifi cally, the server will need to assign the players a
paddle as they connect (left or right).
Serial Communication
fi g. 19.6 Examples 19-6 and 19-7 running together
A nice reward for learning the ins and outs of networked communication is that it makes serial
communication in Processing a breeze. Serial communication involves reading bytes from the computer’s
serial port. Th ese bytes might come from a piece of hardware you purchase (a serial joystick, for example)
or one that you design yourself by building a circuit and programming a microcontroller.
Th is book does not cover the external hardware side of serial communication. However, if you are
interested in learning more about physical computing, I recommend the book Physical Computing: Sensing
and Controlling the Physical World with Computers (Course Technology PTR) by Dan O’Sullivan and Tom
Igoe as well as Making Th ings Talk: Practical Methods for Connecting Physical Objects (Make Books) by Tom
Igoe. Th e Arduino ( http://www.arduino.cc/ ) and Wiring ( http://wiring.org.co/ ) web sites are also excellent
resources. Wiring and Arduino are two open-source physical computing platforms developed at the
Interaction Design Institute Ivrea with a programming language modeled after Processing . I will provide
some accompanying Arduino code for your reference, but the material in this book will only cover what
to do once the data has already arrived in Processing .