ClassNotFoundException in Client when trying to access stub on a different server (Java RMI)

Hello Experts,

I have my server class running on another server. My client is trying to access the remote object and it is throwing the follwoing error:

error unmarshalling return; nested exception is:
      java.lang.ClassNotFoundException: JoptServer_Stub
java.rmi.UnmarshalException: error unmarshalling return; nested exception is:
      java.lang.ClassNotFoundException: JoptServer_Stub

The stub named JoptServer_Stub is available on the server. I am able to successfully bind the remote object to the RMI Engine. I am also attaching the files for your reference.

Please let me know the solution to this problem.

P.S: My client and server are not on the same machine.
Client.java
JoptRemoteCalls.java
JoptServer.java