How to remotely shut down a Java RMI server

Question

I have a very simple Java RMI Server that looks like this:

import java.rmi.*; import java.rmi.server.*; public class CalculatorImpl extends UnicastRemoteObject implements Calculator { private String mServerName; public CalculatorImpl(String serverName) throws RemoteException { super(); mServerName = serverName; } public int calculate(int op1, int op2) throws RemoteException { return op1 + op2; } public void exit() throws RemoteException { try{ Naming.unbind(mServerName); System.out.println("CalculatorServer exiting."); } catch(Exception e){} System.exit(1); } public static void main(String args[]) throws Exception { System.out.println("Initializing CalculatorServer."); String serverObjName = "rmi://localhost/Calculator"; Calculator calc = new CalculatorImpl(serverObjName); Naming.rebind(serverObjName, calc); System.out.println("CalculatorServer running."); } } 

When I call the exit method, System.exit (1) throws the following exception:

 CalculatorServer exiting. java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is: java.io.EOFException at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:203) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:126) at CalculatorImpl_Stub.exit(Unknown Source) at CalculatorClient.<init>(CalculatorClient.java:17) at CalculatorClient.main(CalculatorClient.java:29) Caused by: java.io.EOFException at java.io.DataInputStream.readByte(DataInputStream.java:243) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:189) ... 4 more [2]+ Exit 1 java CalculatorImpl 

What am I doing wrong in this method?

Answer 1

In case someone faces a similar problem, I myself figured out the answer. Here is my exit () method:

 public void exit() throws RemoteException { try{ // Unregister ourself Naming.unbind(mServerName); // Unexport; this will also remove us from the RMI runtime UnicastRemoteObject.unexportObject(this, true); System.out.println("CalculatorServer exiting."); } catch(Exception e){} } 

Answer 2

Actually, only an unregistered and immediately calling System.exit does not close cleanly. This basically terminates the connection before informing the client that the message was completed. What works is to start a small thread that shuts down the system, for example:

 public void quit() throws RemoteException { System.out.println("quit"); Registry registry = LocateRegistry.getRegistry(); try { registry.unbind(_SERVICENAME); UnicastRemoteObject.unexportObject(this, false); } catch (NotBoundException e) { throw new RemoteException("Could not unregister service, quiting anyway", e); } new Thread() { @Override public void run() { System.out.print("Shutting down..."); try { sleep(2000); } catch (InterruptedException e) { // I don't care } System.out.println("done"); System.exit(0); } }.start(); } 

This thread is needed to allow something to happen in the future, still returning from the quit method.