RMI-NAT Problem with random ports

Hi,
I had a RMI server in a machine with the private IP 10.XX.XX.XX and a firewall with the public IP 196.XX.XX.XX
I am using the property: java.rmi.server.hostname to 196.XX.XX.XX and a small test application. The server is behind the firewall/NAT machine with a limited set of open ports (including the non standard 8001 port that I am using instead 1099)
1. The server start perfectly
2. The client can connect to the server and execute the method Naming.list() successfully
3. At the moment that the client attempt to perform the bind, the client hang up for almost 7 minutes and finally throws and exception due time-outs.
According a "strace" and "netstat" commands under Linux and also the flag: java.rmi.server.logCalls we obtain the next data:
1. The server open the port 8001 (PERFECT)
2. But also open a random port and the client -at the bind moment- use that port (in the range 34000-35000). And of course our firewall block all the ports except 8001.
So, is that the expect behaviour? If that is true then RMI is not functional under NAT/Firewall.
Am I missing something?
Thanks!!
Gerardo

Hello,
Let me see if I got it right:
1. You're starting the registry (programatically) in port 8001.
2. You're creating a server implementation object.
3. Next you bind/rebind your server to this registry.
4. Your client hangs at Naming.lookup().
If this is the problem then that random port you mentioned is the server's attributed port (a ServerSocket that is hanging on accept) at the time of creation. You can avoid this by instead of using the super() call in you serverimpl constructor using the UnicastRemoteObject constructor that specifies a port (check the interface). That way you can configure your firewall to allow traffic through that port too.
However, what puzzles me is the fact that it hangs on step 4 instead of in a subsequent remote call. step 4 should be using port 8001. Can you confirm that it's hanging in Naming.lookup ?
(two other sources of data you may find usefull are the Firewall logs and a tcpdump analisys of the traffic between the firewall and the server machine)
Nuno

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