jps can't connect to a remote jstatd

Question

I'm trying query a remote JVM with jps using jstatd, in order to eventually monitor it using VisualVM.

I got jstatd running with the following security policy:

grant codebase "file:${java.home}/../lib/tools.jar" {

    permission java.security.AllPermission;
};

jstatd is running on a 64-bit Linux box with a 1.6.0_10 version HotSpot vm. The jstatd command is:

jstatd -J-Djava.security.policy=jstatd.tools.policy -J-Djava.rmi.server.logCalls=true

I'm trying to run jps from a Windows 7 machine. Due to firewall restrictions, I'm tunneling the RMI data through an SSH tunnel to my Windows machine such that the jps command line is:

 .\jps.exe -m -l rmi://localhost

When I run jps, I see the connection attempt in the jstatd log, which looks like this:

Feb 1, 2011 11:50:34 AM sun.rmi.server.UnicastServerRef logCall
FINER: RMI TCP Connection(3)-127.0.0.1: [127.0.0.1: sun.rmi.registry.RegistryImpl[0:0:0, 0]: java.rmi.Remote lookup(ja   va.lang.String)]

but on the jps side I get the following error:

Error communicating with remote host: Connection refused to host: 192.168.1.137; nested exception is:
    java.net.ConnectException: Connection refused: connect

Based on the connection attempt listed in the jstatd log, I think jps is actually reaching the host, but for some reason is getting blocked. Is there some security policy I have set or some other setting somewhere I can change so that I can get jps to pull stats from the remote jstatd?

It could be that I haven't set the jmxremote properties in the application I want to monitor, as described here: http://stackoverflow.com/questions/726643/get-heap-dump-from-a-remote-application-in-java-using-jvisualvm — afrosteve, Feb 02 '11 at 20:04

score 12 · Accepted Answer · answered Feb 01 '11 at 17:39

12

My guess is that you're only forwarding the RMI registry port (1099), but you need to also open another port.

Check which ports on the remote side

# netstat -nap | grep jstatd

tcp        0      0 :::1099     :::*       LISTEN      453/jstatd          
tcp        0      0 :::58204    :::*       LISTEN      453/jstatd

In this case you will need to forward port 58204 as well as 1099

answered Feb 01 '11 at 17:39

fg.

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No, that didn't help. I tunneled to the other port, 45998 in my case, but jps still could not connect. – afrosteve Feb 01 '11 at 20:18
1

The tunneling didn't help, but opening more ports did. You were right. Thanks. – afrosteve Feb 07 '11 at 17:20
1

@afrosteve: can you explain which other ports you opened and which one you tunneled? – Anthony O. Oct 28 '16 at 15:52

Anthony O. · Answer 2 · 2016-11-03T14:52:29.323

Here is how you could easily do this.

Launch ejstatd in your remote host this way (executing from the ejstatd folder): mvn exec:java -Dexec.args="-pr 2000 -ph 2001 -pv 2002"
Open those 3 ports on your remote host and make them available to your local machine: 2000, 2001 and 2002
On your local machine, you will be able to use jps replacing <remotehost> with your remote host name: jps -m -l rmi://<remotehost>:2000

Disclaimer: I'm the author of the open source ejstatd tool

jps can't connect to a remote jstatd

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