Is it possible to programmatically fill out third-party application forms?

Question

PHP

I have always been interested in solving non-standard problems, and for a very long time a thought has been sitting in my head. Is it possible remotely, for example, by sending requests from a web server, to access the form of a compiled program installed on Windows, suppose it is KeyCoollector or any other program. Fill out the form, get a response and send back. It is clear that you can ask developers for access to the API, however, very often, it is not possible to get good and old API tools.
The following solution comes to mind, there are programs for executing macros on Windows - according to a given scenario, move the mouse and fill in data in certain programs, at certain coordinates, etc. You can algorithmize and automate almost any user action. The essence of the idea: to receive commands from outside to fill in certain fields in certain coordinates, and take the answer from other fields and send it back. In other words, imitate the action of the "intermediary-operator".
I understand that this decision is a cruel perversion and blasphemy, but this will solve the problem. I would be glad to listen to any perversions that will help to suggest an idea for solving this problem.
Here is the problem
"The computer and the Web service are mine, I want the result of the calculation of the software installed on MY computer to be received by the user on the site. And in fact, the user on the site gave the data and the command to MY software about the calculation. However, the software installed ON MY computer was NOT developed by ME.
Sample task in real
life.I have a KeyCollector on my computer.My website has a form to submit keywords.I need a way to deliver the keywords in the KeyCollector to my computer, calculate and return the price to the user on the
site.Question How to link the html form on the site with the form KeyCollectora on my local computer and provide interoperability.

Answer 1

Request to moderators to delete the question.
The author naturally does not know what he wants, all the time bustles, unreasonably complicates the task.
This beaver-suffering is anything but a question.
If, as you say, the client computer belongs to you, then it is not clear what kind of "task" you are basically solving. You write a program that listens to the port, "receives commands from the outside to fill in certain fields in certain coordinates, and from other fields to take the answer and send it back." The task is trivial, but strange. It is not clear why from a web server to climb to a home computer. I have the impression that you need a VPN. Well, or the same radmin/VNC.

Answer 2

https://ru.wikipedia.org/wiki/RAT