Convert a struct sockaddr address to a string, IPv4 and IPv6

sockaddr_tostr.h

// Convert a struct sockaddr address to a string, IPv4 and IPv6:

char *get_ip_str(const struct sockaddr *sa, char *s, size_t maxlen)
{
    switch(sa->sa_family) {
        case AF_INET:
            inet_ntop(AF_INET, &(((struct sockaddr_in *)sa)->sin_addr),
                    s, maxlen);
            break;

        case AF_INET6:
            inet_ntop(AF_INET6, &(((struct sockaddr_in6 *)sa)->sin6_addr),
                    s, maxlen);
            break;

        default:
            strncpy(s, "Unknown AF", maxlen);
            return NULL;
    }

    return s;
}

Or, even better, just call getnameinfo()

char name[INET6_ADDRSTRLEN];
char port[10];
getnameinfo(sa, sizeof(sa), name, sizeof(name), port, sizeof(port), NI_NUMERICHOST | NI_NUMERICSERV);
printf("%s:%s\n", name, port);