Erlang gen server and c++ client

[benefit]

Hello.
Please help me.
I need to make a erlang gen_server which works with an erlang port.
An c++ application must connect to erlang port and send a string. Server should return the same string to the application.

I have troubles working with erlang.
I found an example code :

connect(Message) ->
    Cmd = "./myqtwindowapp \n",
    Port = open_port({spawn,Cmd}, [stream,use_stdio,exit_status]),
    Payload = string:concat(Message, "\n"),
    erlang:port_command(Port, Payload),
    receive
        {Port, {data, Data}} ->
            ?DBG("Received data: ~p~n", [Data]),
        Other ->
            io:format("Unexpected data: ~p~n", [Other])
    after 15000 ->
            ?DBG("Received nothing~n", [])
    end.
 

But i dont know how to run this code. I tried erl -run serv start but recieved error in do_boot. And how to include this code into a small module? Even i recieved error in dbg macros.

Please help me. Suggest me how to finalize. I am newbie here, please suggest me how to run this code or other.
Any help is appreciated.