A C++ Remoting client isn't impossible, but I'm not aware that anyone has ever done it. The client would have to send data that the Remoting server could understand.
I can think of a couple of options.
1. Use the Java Native Interface to put a java layer between the C++ client and the network, where the java layer is a Remoting client.
2. The Remoting HTTP transport can process invocations sent by any HTTP client. So you could have the C++ client generate HTTP requests.