Pass Variables From Php Script To Program Application?

I am developing an VB.NET application that reads data from the serial port and tcp socket, then I'm processing this data and store it in Database server. This application will be started all the time as long as the computer is started. On the server there is installed an apache server with some php scripts representing the "visual interface". From there the users can see the readed data from the VB app. The need is when an event appear in the apache server (such as button pressed), some data to be passed to the running VB app, and eventually trigger an event on it. I've considered some variants like start an timer that reads continuously some tables from the database that the php script writes onto, or read an xml ot text file, but I think that this may slower the communication and it is a source of exceptions or errors.

For example: An user opens a webpage, just to say test.php. On the page there is a button. The user pushes the button. The result of pushing the button has to trigger an event on the VB app and cause sending data trough the serial port or tcp socket. OR - The VB app has a timer that scans for pressing the button on the test.php.