>>>I created a small executable to run a process in the background, so the application does not hang while the process is executed. A timer then checks for the file created and shows the result. I did not use ParallelFox, because I did not want to register any additional libraries at the clients, but not sure if I can succeed.
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>>>Because there is one small problem: When starting the process (using api_Apprun with "HID") the main application loses its focus for a short time. That can be annoying when you are typing or doing anything, and then for a split second the focus goes away, and that every few minutes. So I wonder if there is a way to run the process without losing focus of the calling application, or if there is a way to use ParallelFox without registering, or perhaps another idea?
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>>You can run the process as a service. Or like I used to do, run it on a server or a separate machine. All "communication" with the process is done by sending a file with "instructions", and the process responds by creating a file with the "answers".
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>Yes that could be an idea. So the process stays active in the background and waits for instructions. Only problem, it needs to quit when I close the main application. Of course it was easier to create it in such a way to start it with a parameter, run the process, and then quit, but your solution might be the next best thing and solves the original issue.

One of the instructions sent via the file, can be to shut itself down.