Getaddrinfo Function

Input
hostname (a numeric IPv4/IPv6 addrss or FQDN)
service name (numeric or strings e.g. "http")
Output
all information for socket/bind/connect/whatever
e.g. sockaddr, protocol number, etc.
int getaddrinfo(host, port, hints, res)
    const char *host;
    const char *port;
    const struct addrinfo *hints;
    struct addrinfo **res;

struct addrinfo {
    int ai_flags;
    int ai_family;     /* PF_xxx */
    int ai_socktype;   /* SOCK_xxx */
    int ai_protocol;
    size_t ai_addrlen;
    char *ai_canonname;
    struct sockaddr *ai_addr;
    struct addrinfo *ai_next;
};