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

MAC addresses are used only for the next hop. This basically means the client's original MAC address won't be visible after it's first hop. In the general sense, if you are not on the same physical segment as the client, you have NO way of taking an IP and getting the MAC (or vice/versa).