These routines convert 16 and 32 bit quantities between network byte order and host byte order. On some architectures these routines are defined as NULL macros in
the include file <netinet/in.h>. On other architectures, if their host byte order is different from network byte order, these routines are functional.
These routines are most often used in conjunction with Internet addresses and ports as returned by gethostent() and getservent(). See gethostbyname(3NSL) and getservbyname(3SOCKET).