Rules of thumb (1)

Do not use in_addr and in6_addr
Use sockaddr, sockaddr_in and sockaddr_in6
Using u_long for IPv4 address is out of question - MUST be fixed
in6_addr does not uniquely identify a peer (no scope information)

Do not use functions that deals with in_addr/in6_addr
gethostbyname, gethostbyaddr, getipnodebyname, getipnodebyaddr
inet_ntop, inet_pton, inet_aton, inet_ntoa...