What is the most convenient way to check the passage of traffic through the network?

Question

Computer networks

Greetings gentlemen.
A question.
I set up a test bench from a series of machines (Mikrotik, Linux, Win) to work with VPN channels, routing different networks, etc.
And then I came to the question ...
HOW and WHAT is it easier to generate traffic for a specific protocol / port and receive it on a remote machine?
Maybe there are some utilities that can work in client-server mode (listener-sender).
At the same time, it is very desirable to see from which IP packets come to the listener (server). Speeds/delays - are not interesting.
The task is to check the work of NAT, routing.

THANK YOU VERY MUCH IN ADVANCE.

Answer 1

For routing - mtr
For a higher level - iperf, netcat

Answer 2

nc (netcat) - a console utility for various tasks, including listening to a port and sending data (the simplest console tcp chat works after a connection).

Answer 3

iperf