RMI lookup connect timeout (private IP, proxy, firewall, CGI)
Yuri
I've written an academic application based on RMI and there's one
(last?) major problem that I can't get rid of. Can anybody tell me
what's wrong and whether it can be fixed and if yes how?
The server runs on a Linux machine in a DMZ behind the firewall,
ports 80 (Apache), 1099 (rmiregistry) as well as 4321 (for exported
objects) are open. The server makes callbacks.
Everything works if the client is on a machine with a permanent
IP address and direct Internet connection. It even seems to work
if the client dials in over an ISP.
Now _my_ computer on the campus LAN (different from where the server
runs) has a private IP only (172.x.x.x) and _has_ to use a (Web) proxy
on port 80 to accesss the Internet. A Socks proxy is not available.
DNS resolves the computer name (myhost.mydomain.de) to 172.x.x.x
(from remote subnetworks as well). When I start the client (either under
Windows or Linux), after a couple of _minutes_ an Exception is thrown:
<code>
java -classpath . -Djava.security.policy=./java.policy
-Djava.rmi.server.codebase=
http://serverhost.domain.de:80/path/myclasses.jar
-Djava.rmi.server.hostname=myhost.mydomain.de
-Djava.naming.provider.url=rmi://serverhost.domain.de:1099
-Dhttp.proxyHost=proxy.mydomain.de
-Djava.rmi.server.disable.Http=false
-jar ../client.jar
Objects will be exported to port # 12343
FixedPortSocketFactory.createSocket(serverhost.domain.de:1099)
java.rmi.ConnectException: Connection refused to host:
serverhost.domain.de; nested exception is:
java.net.ConnectException: Operation timed out: connect
java.net.ConnectException: Operation timed out: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:320)
at java.net.PlainSocketImpl.connectToAddress
(PlainSocketImpl.java:133)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:120)
at java.net.Socket.<init>(Socket.java:273)
at java.net.Socket.<init>(Socket.java:100)
at FixedPortSocketFactory.createSocket
(FixedPortSocketFactory.java:40)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:499)
at sun.rmi.transport.tcp.TCPChannel.createConnection
(TCPChannel.java:190)
at sun.rmi.transport.tcp.TCPChannel.newConnection
(TCPChannel.java:174)
at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:318)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Naming.java:84)
at MyMainClass.main(MyMainClass.java:94)
</code>
where
<code>
RMISocketFactory.setSocketFactory(new FixedPortSocketFactory(4321));
public class FixedPortSocketFactory extends RMISocketFactory {
// code skipped here
/** Ignores the parameter and always creates a server socket at
* the fixed port.
*/
public ServerSocket createServerSocket(int port) throws IOException {
return new ServerSocket(fixedPort);
}
public Socket createSocket(String host, int port) throws IOException {
return new Socket(host, port);
}}
</code>
This how I start the server on a remote machine:
<code>
java -classpath . -Djava.rmi.server.hostname=11.10.9.8
-Djava.rmi.server.useLocalHostname=true
-Djava.rmi.server.codebase=
http://serverhost.domain.de:80/path/myclasses.jar
-Djava.security.policy=./java.policy -jar server.jar
</code>
(all computer names and IPs changed for privacy reasons)
I've put java-rmi.cgi to Apache's cgi-bin/ on the server machine,
and it responds with an error message (Java RMI Client Error: can
only forward POST requests) to my "requests" a la
http://serverhost.domain.de/cgi-bin/java-rmi.cgi?forward=1099 in a
web browser - so it is at least launched. Setting
-Djava.rmi.server.disable.Http
to true or false when starting the client changes nothing.
It seems to me like either something has yet to be configured for
HTTP-tunneling (how?) - or the private IP is the problem (or the
proxy). The latter would probably mean that I _can't_ solve this
problem. (Or does FixedPortSocketFactory cause the error?)
Many thanks for your help.
--
Yuri Babich
Student of Computer Science
University of Erlangen-Nuremberg
Germany
Roedy Green
>Now _my_ computer on the campus LAN (different from where the server
>runs) has a private IP only (172.x.x.x) and _has_ to use a (Web) proxy
>on port 80 to accesss the Internet.
I seem to recall browsing a few days ago a paragraph about what you
have to do to force RMI to use HTTP in such a situation. Sorry I
can't give any details other than that the process did not appear to
be automatic.
The java glossary is at
http://www.mindprod.com/jgloss.html
or http://209.139.205.39
--
eagerly seeking telecommuting programming work.
canadian mind products, roedy green
DMB2Step67
your objects within XML and those can cleanly be tunneled though the
HTTP protocol. Hope that gives you a little sense of direction.