getpeername

getpeername 
socket

Returns the packed socket address of the other end of the socket connection. For example:

use Socket;
$hersockaddr = getpeername SOCK;
($port, $heraddr) = unpack_sockaddr_in($hersockaddr);
$herhostname = gethostbyaddr($heraddr, AF_INET);
$herstraddr = inet_ntoa($heraddr);