Java RMI UnmarshalException and AWS EC2 Server

Question

I'm trying to implement the RMI Compute PI tutorial found on the Sun/Oracle website here. The server is located on an Amazon windows EC2 Server. The client is located on my personal computer at home. Just to keep things simple, I have disabled the firewall on the server and open all the port on the EC2 security group. I can ping the machine, have access to files, etc... My aim is just to have a basic RMI program worked on AWS. I will oversee security issues later.

Lauching the server is not a problem. And it's correctly bound to the RMI Registry. I'm using the following command to launch it :

java -Djava.security.manager -Djava.security.policy=C:\AWSTest\security.policy -Djava.rmi.server.codebase=file:/C:/AWS/Sources/sun-rmi-tutorial-server/bin/ file:/C:/AWS/Sources/sun-rmi-tutorial-common/bin/ -classpath C:\AWS\Sources\sun-rmi-tutorial-server\bin;C:\AWS\Sources\sun-rmi-tutorial-common\bin engine.ComputeEngine ec2-XX-XX-XX-XXX.ap-southeast-1.compute.amazonaws.com

The RMI registry is started on the server side.
I have declared a new security manager on the server side System.setSecurityManager(new RMISecurityManager())
I'm using a security.policy file where I'm granted all permission.

When I'm launching the client side, on my local computer, I'm ending with an UnmarshalException:

ComputePi exception: error unmarshalling return; nested exception is: 
    java.lang.ClassNotFoundException: engine.ComputeEngine_Stub
java.rmi.UnmarshalException: error unmarshalling return; nested exception is: 
    java.lang.ClassNotFoundException: engine.ComputeEngine_Stub
    at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
    at java.rmi.Naming.lookup(Naming.java:101)
    at client.ComputePi.main(ComputePi.java:14)
Caused by: java.lang.ClassNotFoundException: engine.ComputeEngine_Stub
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:453)
    at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:184)
    at java.rmi.server.RMIClassLoader$2.loadClass(RMIClassLoader.java:637)
    at java.rmi.server.RMIClassLoader.loadClass(RMIClassLoader.java:264)
    at sun.rmi.server.MarshalInputStream.resolveClass(MarshalInputStream.java:216)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1593)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1514)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1750)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1347)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
    ... 3 more

Do you have any suggestions of what is wrong ? Why can't the client find the correct Stub ? I'm using Eclipse Juno, Genady RMI Plugin and Java 1.7.0_07.

Thanks for your help

EDIT 1 :

The Java workspace is organized around 3 projects : the Client side, the Server Side and a Common project where both the server and the client share classes.

I can read the remote registry from my local computer. The RMI plugin can connect remotely to the server and inspect the registry.
If instead of making 3 projects I put all the classes under the same project, everything is working fine... But I notice that no stubs where generated (or needed).
If, on the client side, I'm putting a reference in the classpath to the server classes (everything being build locally), i have a connection timeout error instead of the unmarshalling error.

ComputePi exception: Connection refused to host: XX.XXX.XX.XX; nested exception is: java.net.ConnectException: Connection timed out: connect java.rmi.ConnectException: Connection refused to host: XX.XXX.XXX; nested exception is: java.net.ConnectException: Connection timed out: connect at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619) at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216) at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:128) at engine.ComputeEngine_Stub.executeTask(ComputeEngine_Stub.java:35) at client.ComputePi.main(ComputePi.java:19) Caused by: java.net.ConnectException: Connection timed out: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:69) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:157) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391) at java.net.Socket.connect(Socket.java:579) at java.net.Socket.connect(Socket.java:528) at java.net.Socket.(Socket.java:425) at java.net.Socket.(Socket.java:208) at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40) at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:146) at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613) ... 5 more

Java RMI UnmarshalException and AWS EC2 Server

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