How to create a program that reads data from another?

Question

For a project I'm trying to create a program that reads data and executes actions in another, but I do not have as much experience with programming yet and I need at least an idea of ​​how it is done.

Answer 1

1.) socket programming
normally you have good libraries to make it not too difficulty(actually it might be difficult for you)

2.)
The first prog writes data to a file, the second one reads them.

3.) Instead of a file use some other cache: mqtt, cookies,whatever...

Answer 2

Thanks a lot