Question

I am trying to send an object in java over a physical network (not over localhost) but it seems I have something wrong.

The interface to the object (client and server have this):

public interface distributable extends Serializable {

      public void test();
}

The Object I am trying to send (only server has this):

class ObjectToSend implements distributable {

       public ObjectToSend() {
       }

       public void test() {
            system.out.println("worked!");
       } 
}

Server:

private ObjectToSend obj = new ObjectToSend();

obj_out_stream.writeObject(obj);
obj_out_stream.flush();

Client:

private distributable ReceivedObj = null;

try {
       ReceivedObj = (distributable) obj_in_steam,readObject();
} catch (ClassNotFoundException e) {
       System.err.println("Error<w_console>: Couldn't recieve application code!");
} 
ReceivedObj.test();

Everything was working when the ObjectToSend class implemented Serializable and I wasn’t using an interface because all my classes were in one directory so the client ‘knew’ about the object. Now I want it to work across a physical network so the client only has the interface to the object. It seems that client can not receive the object as the exception is thrown every time.

Answer 1

As the other answers suggest, the Client also has to know the class of the object you want to send.

Usually, one creates three packages/projects for such a classic client-server example:

Common: Code that is used by client and server; the class definition of the objects you want to send from the server to the client belongs here

Client: All code only the client needs to know about

Server: All code only the server needs to know about