Page 267 - Hacking Roomba

248 Part III — More Complex Interfacing

Controlling Roomba through a Web Page

Roomba is now on a wireless network, but to make it usable, it needs something external to
send it proper ROI commands. You could use RoombaComm as you’ve done previously, but
network accessibility opens up an entirely new space to play in. On the Internet there are pro-
gramming languages that normally don’t touch hardware, but now you control Roomba with
them. Some of those languages are part of the LAMP web application platform. You can create
a dynamic web page to control Roomba and have that page live anywhere on the Internet that
has a LAMP-compatible server.

LAMP

LAMP is a suite of open source tools connected together to create dynamic web sites. It usually
stands for Linux, Apache, MySQL, PHP, but P can also stand for Perl or Python. The great
thing about LAMP is that it’s more of a methodology than a specific set of technologies.
Different pieces can be added or swapped around as the need arises. In fact, the LAMP philos-
ophy isn’t bound to Linux. There is also WAMP for Windows and MAMP for Mac OS X.
For the following purposes, PHP on Apache will be used as the basic arrangement. The term
LAMP will be used to refer to all similar setups, unless there are some WAMP- or MAMP-
specific configuration issues.
The components of LAMP are part of every modern Linux distribution. To get WAMP for
your Windows box, visit www.wampserver.com/. To get MAMP for Mac OS X, visit
www.mamp.info/.

Both PHP and Apache will tell you when something is amiss by writing the errors to special
log files. When debugging web programs, one of the easiest and most instructive techniques
to find problems is to watch these files. This is sometimes called tailing the logs after the Unix
practice of typing tail -f logfile. The tail -f command shows the last few lines of a file
and will follow the end of the file as more is written to it. In LAMP environments the two
most important logs are:

error_log: The Apache error log. This shows web site configuration and page
access errors.
php_error_log: The PHP error log. This shows syntax and execution errors for
PHP pages.
In MAMP systems both of these logs are located in /Applications/MAMP/logs. In
WAMP systems both are located in C:\WAMP\logs. Various Linux distributions put the
logs and other components in different locations.