I don’t have doubts that the question was asked — it just does not really belong to “API testing” topic. It’s common that some company want to test if the person they may hire is skilled with Java and Test NG, but that is not really about API testing.
You can run requests from Postman, SoapUI, Jmeter, many other tools in different languages. There is no any particular need to use TestNG for that.
I’d put the topic like you added it below the title: “How can I read the input data from HTTP source every x seconds in TestNG?”