Easiest way to get MAC address from a (non-local) IP address in IPv4

Question

Is there an easy way to get a MAC address of a machine connected to my app via a TCP/IPv4 socket?

Or in more general terms:

If I have the IP address, what

Answer 1

It is the ARP table's job to keep that information. The best thing to do would be to read it out of there.

You might consider reading the answers to Query ARP cache to get MAC ID. The questioner was using Java, but otherwise its your identical question.