How to make sure that single instance of Java Web Start application is running on client's machine?

Question

I am trying to execute .jnlp file on client machine using java web start as well as open web start. How to make sure that only single instance of jnlp application or java web start application is running on client's machine? I found that need to use SingleInstanceService and SingleInstanceListner interfaces, but not getting how to use that. Can anybody give example? Thanks in advance