The Visual Test Shell (or VTS) is a free and open source software. This application is used for testing the BACnet functionality of various devices used in building automation systems.
The application can “generate BACnet compliant service messages, detect and decode BACnet compliant service messages, and run scripts to generate, receive and respond to BACnet compliant service messages.” (VTS3Guide.doc)
The project home page can be found here: http://vts.sourceforge.net/
You can download the application here: http://sourceforge.net/projects/vts/
The version of VTS, at the time of the writing of this article, is 3.5.5.
The VTS is a testing suite that is listed by the BACnet Testing Laboratories and BACnet.org (http://www.bacnet.org/Developer/index.html) as a useful open source tool for testing your own BACnet implementations.
For more information on the project or to find some help, visit their forums at: http://sourceforge.net/projects/vts/forums/forum/86056