bool isIPV6Net(const std::string ip_v4, std::string& out_ip)
{
    bool is_v6 = false;

    struct addrinfo* res0;
    struct addrinfo hints;
    struct addrinfo* res;

    memset(&hints, 0, sizeof(hints));
    hints.ai_flags = 0;
    hints.ai_family = PF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    int n = 0;
    if((n=getaddrinfo(ip_v4.c_str(), "http", &hints, &res0))!=0)
    {
        printf("getaddrinfo error: %s\n",gai_strerror(n));
        return false;
    }

    struct sockaddr_in6* addr6;
    struct sockaddr_in* addr;
    char ipbuf[32] = {‘\0‘};

    for(res = res0; res; res = res->ai_next)
    {
        if(res->ai_family == AF_INET6)
        {
            addr6 =( struct sockaddr_in6*)res->ai_addr;
            inet_ntop(AF_INET6, &addr6->sin6_addr, ipbuf, sizeof(ipbuf));
            is_v6 = true;
        }
        else
        {
            addr =( struct sockaddr_in*)res->ai_addr;
            inet_ntop(AF_INET, &addr->sin_addr, ipbuf, sizeof(ipbuf));
        }
        break;
    }
    out_ip = ipbuf;
    return is_v6;
}

char ipv4[4] = {192, 168, 2, 119};
char ipv4_str_buf[INET_ADDRSTRLEN] = { 0 };
const char *ipv4_str = inet_ntop(AF_INET, &ipv4, ipv4_str_buf, sizeof(ipv4_str_buf));

std::string out_ip;
bool is = isIPV6Net("64:ff9b::739f:62d", out_ip);