If you are interested in monitoring a switch with the General Purpose Input / Output included with the Digi TransPort WR31, here are some easy instructions that can get you up and running quickly!  A video walkthrough is available for this procedure at:
http://www.digi.com/videos/using-the-gpio-on-transport-wr31
 
This example covers Digital I/O, but analog works and is configured in a very similar manner.
 

Components Needed:

  Safety note: Always disconnect power from any Digi router before performing a wiring task.
 

Wiring:

For this demonstration project, you will only use pins 2 & 3 (ground and DIO 0) on the WR31 terminal block.  The order in which you attach the wires will determine whether the DIO reading changes to high or low when the circuit closes or opens.
 
If your results are the opposite of what you expect, try reversing the wires for your setup:
 
Your wiring setup should look something like this:
 

Configure the WR31

In the WR31 configuration interface, use the path:
Configuration – Telemetry > GPIO

 

When you complete the configuration on your Digi router, click the “Apply” button, then save the configuration.
 

Software:

You will need to download and “upzip” the free Netcat application to use it.  Netcat is a command line application available for Unix and Windows.  Syntax is straightforward:
Launch app         -L (listen)  -p 2020 (port 2020)
nc64.exe –L –p 2020

Results:

Now it’s time to test your setup by launching Netcat on your PC, then pressing and releasing the button wired to your WR31.
 
Below is what you should expect to see when you launch Netcat and work with the switch you wired into the WR31 terminal block: