How to debug a web application?

Question

Java

I am writing an application with the ability to work through the network in the same mode as if it worked not through the network but with the native console. I'm trying to test it through the telnet utility, the lines I enter reach the application, but I don't get any answers, what should I do? How else can you test the application? I understand that the easiest way is to write some simple "client" of your own, but still?

Answer 1

And the application in response writes something in principle?