If while trying to use Java RMI you ever see an error like:

java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: scifly.scanner.rmi.SerialPortServer_Stub


Go and check the CLASSPATH that was set from where you started the rmiregistry.exe (ie. the middleware server, as I think of things). Chances are very good that your project classes were not in the classpath for the rmiregistry. That error message is the rmiregistry complaining that it can’t find your class, NOT your client code.

This took me a little while to work out, so I thought I’d preserve it here, for when I forget again …