coding: "write a socket listener that reads from a buffer and converts it into a null-terminated string".

solving a problem: write a program that does (some open-ended business problem). Or generalize the socket listener so that it works on any platform, OS, hardware, network configuration, etc.

A coder might do great on confined problem space, but when you ask them to write a larger program they dont normally know how to design it. This isn't just true of bootcamp coders though. Tons of CS grads wouldn't do any better. Otherwise FizzBuzz would have never been a thing.