resolve: Host not found (authoritative), while using http_listener() of CPPrest sdk

Question

below is the piece of server side code, written in c++:

utility::string_t port = U("8080");
utility::string_t address = U("http://service-ricxapp-bouncer-xapp-http.ricxapp:");
address.append(port);
address.append(U("/ric/v1/subscriptions/response"));
uri_builder uri(address);
auto addr = uri.to_uri().to_string();
http_listener listener(addr);
cout<<uri::validate(addr)<<"\n"; //--------> this is printing 1

I am running this piece of code in Ubuntu 18