Writing a service in C: How to pass and process arguments to running service?

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http://unix.stackexchange.com – I want to write a service in C. While this service is running in background and processing some information I need to grab the results from this service from other applications or from command line. Background: I need a C application/service due to performance issues. The UI will be implemented in a higher language like Java or C#/Mono on Linux. The C application will basically process data, which will come in from another source. The UI layer should be able to grab the results in a loop every few milliseconds for example and display it to the user. Also it should be possible to pause/start (HowTos)