Computers may use either big-endian or little-endian byte order. On the Internet, data are always in network order, which is big-endian. For little-endian machines, such as Intel x86 based PCs, a set of library functions, htons(), htonl(), ntohs(), ntohl(), are available for converting data between host order and network order. For example, a port number 1234 in a PC is an unsigned short integer in host (little- endian) byte order. It must be converted to network order by htons(1234) before using. Conversely, a port number received from the Internet must be converted to host order by ntohs(port).
Source: Wang K.C. (2018), Systems Programming in Unix/Linux, Springer; 1st ed. 2018 edition.