zkArpaInet.h is a portable wrapper for the Unix 98 header <arpa/inet.h>. It is part of the libzk library because <arpa/inet.h> doesn't exist in Standard C.

zkArpaInet.h - Supported Functions from <arpa/inet.h>
htonl
htons
ntohl
ntohs

zkArpaInet.h - Deprecated Functions from <arpa/inet.h>
Don't Call This Instead, Call This Reason
inet_addr zkInet_addr Not in Standard C.
inet_ntoa zkInet_ntoa Not in Standard C.
inet_aton zkInet_aton Not in Standard C.