Calling Java Methods in a windows java service

I want to be able to allow a C programme to interface with my Java Service.

I know I can use the JNI to allow the C programme to talk to Java, but how can I get the C programme to talk to Java if it is running as a windows java service?

Thanks in advance for any advice.

This sounds like a job for socket communication. Your Java program can establish a java.net.ServerSocket and listen for requests from the C program. Once a connection is established, start a Thread to accept the data from the C program, process it and return the result.
I believe we have a whole forum here for socket related programming.
Bill