In socket programming in C++ WIN32 / UNIX / LINUX , we use AF_INET for Address family and PF_NET for protocol family.

socket( AF_INET, SOCK_STREAM, IPPROTO_IP )
serv_addr.sin_f amily = AF_INET;

socket( PF_INET, SOCK_STREAM, IPPROTO_IP )
serv_addr.sin_f amily = PF_INET;

I would like to know where we need to use AF_NET & PF_NET respectively?