What homework test for junior C++ would you recommend?

Question

C++ / C#

Citizens!
We need to come up with a short test task for Junior, which would test the most basic knowledge of multithreading and networking (TCP or UDP). It will be offered to candidates BEFORE the interview.
I have this idea so far: the client sends the coefficients of the quadratic equation to the server, the server solves it asynchronously and returns the answer. But something it does not shine with originality, and not as short and simple as we would like.
Thank you!

Answer 1

Build a histogram of "War and Peace" in one thread.
Build it in several.
Measure the time, justify the choice.

Answer 2

Distributed vector-matrix multiplication.
Complications:

• Use UDP-multicast
  
• Ensure that all cores are fully loaded on all machines.
  

Answer 3

Distributedly compile an application from multiple .cpps