The second program in the request-response example, server.cpp, uses the reply-to property as the routing key for responses.

The main body of server.cpp creates an exclusive queue for requests, then waits for messages to arrive.

string request_queue = "request";

session.queueDeclare(arg::queue=request_queue);
session.exchangeBind(arg::exchange="amq.direct", arg::queue=request_queue, arg::bindingKey=request_queue);

SubscriptionManager subscriptions(session);
Listener listener(subscriptions, session);
subscriptions.subscribe(listener, request_queue);

subscriptions.run();

The listener's received() method converts the request's content to upper case, then sends a response to the broker, using the request's reply-to property as the routing key for the response.

void Listener::received(Message& request) {

  Message response;
  string routingKey;

  if (request.getMessageProperties().hasReplyTo()) {
    routingKey = request.getMessageProperties().getReplyTo().getRoutingKey();
  } else {
    std::cout << "Error: " << "No routing key for request (" << request.getData() << ")" << std::endl;
    return;
  } 

  std::cout << "Request:: " << request.getData() << "  (" << routingKey << ")" << std::endl;

  // Transform message content to upper case
  std::string s = request.getData();
  std::transform (s.begin(), s.end(), s.begin(), toupper);
  response.setData(s);

  // Send it back to the user
  response.getDeliveryProperties().setRoutingKey(routingKey);
  session.messageTransfer(arg::content=response, arg::destination="amq.direct");
  
  if ( request.getData() == "That's all, folks!" )
    dispatcher.stop();
}