getnameinfo

Input
sockaddr
Flags to indicate what you want to get
Output
FQDN, or numeric IP address in string
Service name, or numeric servicde number in string

int getnameinfo(sa, salen, host, hlen, port,
        plen, flags)
    const struct sockaddr *sa;
    socklen_t salen;
    char *host;
    size_t hlen;
    char *port;
    size_t plen;
    int flags;