I want to set something up on my computer where if something (program, browser, whatever) makes a request (to a certain domain, I guess) I can send my own response to the request. I once saw a program that did that, and I was wondering how it did it. How would it be done?
How about just editing hosts file? Popular operating systems have it. Just use it to redirect to whereever you want. To me it looks like the simplest solution to this question.