Rules of thumb (2)

Use struct sockaddr if it is a pointer.
Use struct sockaddr_storage if it is an actual variable.
Never use sockaddr as placeholder, because sockaddr_in6 is larger.

Be careful about sizeof(struct sockaddr_in) or sizeof(sa)
"sa_len" should be used in most occasions
Linux/Solaris is a problem - maybe use SA_LEN?
ai_addrlen can be used when you use getaddrinfo().

Use getaddrinfo() and getnameinfo() throughout the system