http credentials setting gets 401 error

[serenity103]

//Basic Authorization Setting
http_client_config config;
credentials creds(L"name", L"password");
config.set_credentials(creds);
http_client client(U("http://severip/"), config);

// create header
http_request req(methods::GET);

//// Add base64 result to header
req.headers().add(L"Authorization", L"Basic bmFtZTpwYXNzd29yZA");
pplx::task<http_response> responses = client.request(req);
pplx::task<web::json::value> jvalue = responses.get().extract_json();
web::json::value v = jvalue.get();
utility::string_t jsonval = v.serialize();
wcout << jsonval << endl;

//with base64 encoding.
//bmFtZTpwYXNzd29yZA = name:password

I'm trying to set a credentials through cpprestsdk aka casablanca.

And I've received 401 error which is failed to authenticate user, it means password error.

The server where I wanna send a query is elastic-search's cluster.

Any advice would be thankful.