rmi - ConnectException - rmi

Question

This is my first time that I am using RMI, basically I manage to run the following RMI example locally on my PC but not via two separate Linux machines.
The server interface:
public interface PowerService extends Remote{
public BigInteger square ( int number )
throws RemoteException;
public BigInteger power ( int num1, int num2)
throws RemoteException;
}
The server:
public class PowerServiceServer extends UnicastRemoteObject implements
PowerService {
public PowerServiceServer() throws RemoteException {
super();
}
public BigInteger square(int number) throws RemoteException {
imp .....
return (bi);
}
public BigInteger power(int num1, int num2) throws RemoteException {
imp .....
return bi;
}
public static void main(String[] args) throws Exception {
PowerServiceServer svr = new PowerServiceServer();
// ... and bind it with the RMI Registry
Naming.bind("PowerService", svr);
System.out.println("Service bound....");
}
}
The client:
public class PowerServiceClient {
public static void main(String args[]) throws Exception {
// Call registry for PowerService
PowerService service = (PowerService) Naming.lookup("rmi://" + args[0]
+ "/PowerService");
DataInputStream din = new DataInputStream(System.in);
for (;;) {
System.out.println("1 - Calculate square");
System.out.println("2 - Calculate power");
System.out.println("3 - Exit");
System.out.println();
System.out.print("Choice : ");
String line = din.readLine();
Integer choice = new Integer(line);
int value = choice.intValue();
switch (value) {
case 1:
// Call remote method
....................
break;
case 2:
// Call remote method
....................
break;
case 3:
System.exit(0);
default:
System.out.println("Invalid option");
break;
}
}
}
and the client interfaces is the same like the server
This is what I did in order to run the rmi example:
1) On the server side I created the stub
2) Run rmiregisrty
3) Run the server
4) I copy the stub from the server side to the client side in to the same package
5) Run the client
After running the client I got the following error message:
Exception in thread "main" java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is:
java.net.ConnectException: Connection refused
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:601)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:198)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:184)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:110)
at compute.PowerServiceServer_Stub.square(Unknown Source)
is possible that due to some firewall I can’t connect or perhaps I am doing something wrong ??
Thanks

Answer 1

This is the problem addressed by java.rmi.server.hostname. See item A.1 in the RMI FAQ. You need to either fix the /etc/hosts misconfiguration that causes it, or set the system property java.rmi.server.hostname in the server JVM to the correct IP address of the server, before exporting any remote objects.