gethostbyaddr

gethostbyaddr address, [addrtype]

Retrieves the hostname (and alternate addresses) of a packed binary network address. (addrtype indicates the type of address given. Since gethostbyaddr is used almost solely for Internet IP addresses, addrtype is not needed.) The return value in list context is:

($name, $aliases, $addrtype, $length, @addrs)

where @addrs is a list of packed binary addresses. In the Internet domain, each address is four bytes long and can be unpacked by saying something like:

($a, $b, $c, $d) = unpack('C4', $addrs[0]);

In scalar context, gethostbyaddr returns only the hostname.