How to configure Apache in MAMP to only be accessible from the machine it is installed on

For a number of reasons I wanted to run a web application locally on my MacBook.  After some research I decided that the path of least resistance was to install the free MAMP app, which runs an Apache-MySQL-PHP stack on a Max OS X machine without having to do a complex install process.   I got my web app working on MAMP pretty easily, but then I discovered that other machines on my local network could also access the web app if they connected to the right port of the IP address of my MacBook.  That isn't a problem when I am at home or work, but I didn't want the web app exposed when I was on public networks like at a coffee house or the library.  After some research I discovered the solution was to edit the /Applications/MAMP/conf/apache/httpd.conf file to change:

Listen 8888

to

Listen 127.0.0.1:80

This did two things. It changed the port that MAMP uses from the MAMP default of 8888 to 80 (the normal web server port) and specified that only traffic from the local machine would be accepted.  After I made this change and restarted the Apache server I was no longer able to access the web app from other machines on the same network.