public RegistryServer(int port) {
		try {
			// listen at a given port
			serverSocket = new ServerSocket(port);
		} catch (IOException e) {
			System.out.println(e.getMessage());
			System.out.println("Fail to listen on port " + port);
		}
		System.out.println("Registry server started, listening on port " + port);
		rortbl = new Hashtable<String, RemoteObjectRef>();
	}