std::string connection_string = "mongodb://user:cooPh5ohcei0Iewe@xxxx:27017/";
mongocxx::instance inst{};
mongocxx::client conn{mongocxx::uri{connection_string}};

std::cout << "username: " << conn.uri().username() << std::endl;
std::cout << "password: " <<  conn.uri().password() << std::endl;

auto db = conn["fastnetmon"];
std::string collection_name = "configuration";

if (!db.has_collection(collection_name)) {
    std::cout << "Connection failed" << std::endl;
}
{/code}

From Mongo's side I haven't saw any auth tries: