Wt

#include <Wt/WServer>

#include <Wt/WResource>

#include <Wt/Http/Client>

#include <Wt/Http/Response>

#include <memory>

#include <atomic>

#include <iostream>

// CMD:

// C:> server.exe --http-address 0.0.0.0 --docroot .

// Terminal (in parallel):

// $ while [ "$(curl -s 'http://localhost/FetchData')" == "done" ]; do   echo -n '.';   sleep 1; done

class FetchData : public Wt::WResource {

public:

   FetchData (Wt::WServer& server) : server(server) { }

   ~FetchData () override { beingDeleted(); }

   void handleRequest (const Wt::Http::Request& /*request*/, Wt::Http::Response& response) override 

   {

      std::atomic<bool> done = false;

      auto client = std::make_unique<Wt::Http::Client>();

      client->done().connect([&] (boost::system::error_code err, const Wt::Http::Message& /*response*/, ...) {

         if (err) server.log("error") << err.message();

         done = true;

      });

      if (client->get("http://localhost/data")) {

         while (!done) {

            boost::this_thread::sleep_for(boost::chrono::milliseconds{25});

         }

      } 

      else {

         server.log("error") << "something is wrong with the url";

      }

      response.out().write("done", 4);

   }

private:

   Wt::WServer& server;

};

class ServeData : public Wt::WResource {

public:

   ServeData () = default;

   ~ServeData () override { beingDeleted(); }

   void handleRequest (const Wt::Http::Request& /*request*/, Wt::Http::Response& /*response*/) override 

   {

   }

};

int main (int argc, char** argv) 

try {

   Wt::WServer wserver{argc, argv};

   FetchData fetchdata(wserver);

   wserver.addResource(&fetchdata, "/FetchData");

   ServeData servedata;

   wserver.addResource(&servedata, "/Data");

   wserver.run();

   return 0;

}

catch (std::exception& e) {

   std::cerr << e.what() << std::endl;

   return 10;

}