simple secured remote procedure call

I have an application written in C++. The application is compiled into a library. I am looking for an experienced guru to achieve: 1) provide server-client service: when client sends data, the server will return output to client. Both input and output data are simple. (See below) 2) it will be machine independent. Ideally, the server OS will be UNIX/Linux/C++. At the client side, It will work on both linux and windows. 3) client can use C++ language to program/call. As client code can be built into a library (dll, lib, so), other language can also call the library directly. As such, I feel that C++ at the client side would be sufficient. 4) there will be no database. 5) security: As service is based on a secure connection, client's identity will need to be verified in order to connect with the cloud server and use cloud services. 6) I will install an AWS server. You provide code and make it work. 7) There will not be more than 5 clients in total. 8) I heard something called remote procedure call can solve. 9) The speed of call has to be quick. For illustration purpose, input data in C++ struct Parameter { double d1; double d2; double d3; double d4; int i1; int i2; vector v1; }; struct Product { int i1; int i2; double d1; }; struct Data { double d1; int i1; vector v1; }; The data will send to server. For illustration, services include vector helloworld1(Parameter p, Data d); boolen helloworld2(Data d); The outputs (vector , boolen) from calls will send back to the client. !!! It is worth mentioning that the helloworld1, helloworld2 functions will be implemented by me, You don't need to code them. !!! I just need a bit support on the deployment side. Please let me know what approach you will use, how long it will take and your proposed budget. If you have any question, please let me know.