In the `on_message()` method in the `simple_recv` example, add the following lines:

std::string host = d.connection().virtual_host();
std::cout << "Message from " << host << std::endl;

Send a message. The hostname is empty. I have not been able to find a place in the lifecycle of a simple Proton program where this value is non-empty.

It would be helpful in scenarios where load balancing or failover are in use, to be able to log to which broker a client is connected. I seem to recall that this was possible in earlier versions of Proton.