RMI app behind NAT firewall

[tobias.weih]

I have a problem getting my RMI application to work. Having a RMI
Server app running in a VMWare that forwards port 1099 in a NAT
enviroment.
Physical machines IP on the outside = 9.154.38.47
Physical machines IP in local area = 192.168.0.1
Virtual machines IP = 192.168.0.100

I start a rmiregistry on my virtual machine and since port 1099 is
NAT-forwarded I can connect to the registry from the outside using
telnet 9.154.38.47:1099.

I startup my serverside rmi-app on the virtual machine
-Djava.rmi.server.hostname=$HOST


and in my app I do the following binding:
System.getProperties().put("java.rmi.server.hostname", HOST);
Registry reg = LocateRegistry.createRegistry Registry.REGISTRY_PORT);
Naming.rebind("//"+ HOST + ":1099/" + CommandBroker.NAME, this);


This work fine with HOST=127.0.0.1 or HOST=192.168.0.100 but when
setting HOST=9.154.38.47 (the public IP address), startup fails with:

java.rmi.AccessException: Registry.Registry.rebind disallowed; origin
/9.154.38.47 is non-local host

When server is running with HOST=127.0.0.1 or HOST=192.168.0.100 (like
I said using HOST=9.154.38.47 doesn't work at all, the server is not
allowed to bind) the binding from the outside using my client-app works
(bind to 9.154.38.47 the public IP) , but however when trying to
actually use the remote object the client throws the following
exception:
Using HOST=127.0.0.1 on serverside

Operation timed out: connect:could be due to invalid address

or when server HOST=192.168.0.1

java.net.ConnectException: Connection refused: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:585)


I assume using the public IP on serverside by setting HOST= to
9.154.38.47 is the right way, but as stated above binding to the
rmiregistry is not allowed! What am I missing?

Thanks alot, your help is very much appreciated.
Cheers,
Tobi

 

[tobias.weih]

my problem is solved, finally. There are a couple of things that caused
my troubles:
First of all, binding to localhost is correct, since the host-address
is only used
to contact the registry for the rebind operation. When using the public
IP to bind
it fails because the connection to 9.154.38.47 is being routed out to
the NAT and
back in again, so its origin appears non-local. And as a rule binding
to a non l
ocalhost is forbidden.
As far as an external client being able to use the bound stub, the
important setting
is the java.rmi.server.hostname system property, which controls the
host name or
address that gets put into the stubs for remote objects exported in
this VM. Thus
it has to be 9.154.38.47 in my case.
Another very interessting thing is the need to explicitly define the
port the
Remote Object uses. Therefor I call super(1099) instead of just
super().
See
http://archives.java.sun.com/cgi-bin/wa?A2=ind0302&L=rmi-users&P=3663
for details.

tobi