How do you understand the work of the following command?

Question

linux

there is a command:

#!/bin/bash
if [ "$(echo PING | nc localhost 3010)" = "PONG" ]; then
  echo "ping successful"
else
  echo "ping failed"
  exit 1
fi

why does it return PONG (we have a tcp server running on 3010)? Is this the response to start establishing a tcp connection?

Answer 1

It all depends on the software that hangs on port 3010 - if in response to the PING line it in some cases answers PONG.