After starting tomcat with jpda on, while at my company I can remote debug a bunch of web applications in eclipse. For a number of reasons I am now in need of developing and remote debugging those same webapps from outside the company firewall, and i can only access that server via ssh on port 22.
I tunneled most needed ports (svn, nexus, tomcat itself, from the server or via the server) to localhost and those services work fine, but I cannot start the eclipse debugger in any way; i'm getting "connection timed out while waiting for packet XXX" or "connection refused" from the second time i try on.
Checking with nmap on the server, it reports the port open before the first connection attempt, and it becomes closed after that. I get no interesting output log in catalina.out
The command i use to start the tunnel is:
ssh -L 8000:localhost:8000 user#mycompany.com
iptables was temporarily stopped both on the server and in the local machine for testing.
Am i missing something? Do I need to forward some other port to localhost? Or is it in some way involved name resolution?
EDIT
Open ports before connection attemp from eclipse:
root#lnxulisse:/opt/apache-tomcat-6.0.32/bin# lsof -p 2147 -n |grep TCP
java 2147 root 4u IPv4 640850 0t0 TCP *:8000 (LISTEN)
java 2147 root 38u IPv6 640859 0t0 TCP *:http-alt (LISTEN)
java 2147 root 40u IPv6 640865 0t0 TCP *:https (LISTEN)
java 2147 root 46u IPv6 640908 0t0 TCP 127.0.0.1:18005 (LISTEN)
java 2147 root 48r IPv6 642625 0t0 TCP 172.24.0.82:48347->172.24.0.82:mysql (ESTABLISHED)
java 2147 root 181u IPv6 640891 0t0 TCP 172.24.0.82:60353->172.24.0.82:mysql (ESTABLISHED)
and after:
java 2147 root 4u IPv6 642769 0t0 TCP 172.24.0.82:48956->172.24.0.82:mysql (ESTABLISHED)
java 2147 root 5u IPv4 640851 0t0 TCP 127.0.0.1:8000->127.0.0.1:34193 (ESTABLISHED)
java 2147 root 38u IPv6 640859 0t0 TCP *:http-alt (LISTEN)
java 2147 root 40u IPv6 640865 0t0 TCP *:https (LISTEN)
java 2147 root 46u IPv6 640908 0t0 TCP 127.0.0.1:18005 (LISTEN)
java 2147 root 181u IPv6 640891 0t0 TCP 172.24.0.82:60353->172.24.0.82:mysql (ESTABLISHED)
exact eclipse error returned is:
Exception occurred during launch
Failed to connect to remote JVM. Connection timed out.
Timeout occurred while waiting for packet 204.
(the packet number varies on each attempt).
in workspace/.metadata/.log i get:
!ENTRY org.eclipse.osgi 2 0 2011-07-17 18:43:53.024
!MESSAGE While loading class "org.eclipse.core.net.proxy.IProxyService", thread "Thread[main,6,main]" timed out waiting (5000ms) for thread "Thread[Thread-6,5,main]" to finish starting bundle "org.eclipse.core.net_1.2.1.r35x_20090812-1200 [232]". To avoid deadlock, thread "Thread[main,6,main]" is proceeding but "org.eclipse.core.net.proxy.IProxyService" may not be fully initialized.
!STACK 0
org.osgi.framework.BundleException: State change in progress for bundle "reference:file:plugins/org.eclipse.core.net_1.2.1.r35x_20090812-1200.jar" by thread "Thread-6".
at org.eclipse.osgi.framework.internal.core.AbstractBundle.beginStateChange(AbstractBundle.java:1073)
at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:278)
[...]
!ENTRY org.eclipse.ui.ide 4 4 2011-07-17 18:43:53.028
!MESSAGE Proxy service could not be found.
eclipse is configured for direct internet connection.
EDIT 2
I think the solution might be here:
http://blog.cantremember.com/debugging-with-jconsole-jmx-ssh-tunnels/
but i have some trouble understanding his JNDI/RMI settings, and to what extent that applies to my configuration.
EDIT 3
This is a clarification for those answering "use <lan|local ip address> instead of <localhost>"
computer A: my workstation in the company
computer B: my workstation at home
computer C: server running tomcat
B and C are in two different sub-networks in the same network infrastructure; only connections to port 22 of C from outside are allowed (and somewhat "proxied", I don't know network internals).
A is "outside" (my dsl connection with dynamic ip address).
Debugging on C from B via ssh tunnel -> works
Debugging on C from A via ssh tunnel -> connection timed out while waiting for packet XXX
This article suggests that the default port on which the remote Java virtual machine (JVM) is listening in debugging mode is 1044. You should tunnel the port on which the remote JVM is running as well.
More generally, you could run wireshark/tcpdump to see to which port connection attempts are made when starting the debugger.
EDIT:
A few more things I would try:
check on the remote host (e.g. with ps auxwww if it's Linux) with which arguments (look for what comes behind -Xrunjdwp or with lsof -p PID_OF_JVM_TO_BE_DEBUGGED on which TCP port it listens (look for lines with TCP and LISTEN in the lsof output)
make sure that the JVM on the remote host listens on the lo interface, not the network interface (that's what you specify with the localhost in the -L option to ssh).
Does starting the debugger by hand on the machine where you start eclipse with jdb -attach localhost:8000 work ? (you could also try this on the remote host to ensure the debugger is running on the port 8000)
make sure that eclipse tries to connect to localhost (when not specifying a bind address before the first 8000 with the -L option ssh listens on the lo interface)
I often had this problem when doing remote debugging. I do not know the exact reason for this problem, but I used the below solution and maybe it works for you, too:
instead of
ssh -L 8000:localhost:8000 user#remotehost
is used
ssh -L 8000:remotehost:8000 user#remotehost
for creating the SSH tunnel (note the remotehost instead of localhost between the port numbers in the second example). Instead of the remote host's name, you can also use the normal IP address of the remote host (not the loopback address 127.0.0.1, but the true local network IP address).
Hope it helps and good luck!
Assuming the remote Tomcat instance has been started with something like -Xrunjdwp:transport=dt_socket,server=y,address=8000,suspend=n, try this command:
ssh -L 8000:0.0.0.0:8000 user#mycompany.com -N
On my Mac, I tried out ssh -L 10701:localhost:10700 user#localhost -N locally, where a Tomcat instance was started with -Xrunjdwp:transport=dt_socket,server=y,address=10700,suspend=n, and attempting to attach on port 10701 within Eclipse, I kept seeing "Failed to connect to remote VM com.sun.jdi.connect.spi.ClosedConnectionException". By changing the tunnel command to ssh -L 10701:0.0.0.0:10700 user#localhost -N, Eclipse was able to attach.
Can you please give the exact parameters of the -Xrunjdwp parameter?
Also do you have tried different methods for debugging (server=y/n, suspend=y/n)?
Perhaps inversing the connection (let the tomcat connect to the debugger instead of letting the debugger connect to tomcat) may help.
Well I am answering myself after a long time; in my specific case, the solution was to put eclipse JVM in listening mode:
Connection Type: "Standard (Socket Listen)"
and reverse the direction of the tunnel:
ssh -L 8001:localhost:8001 user#work (run on server (S), "localhost" is W)
ssh -R 8001:localhost:8001 user#work (run at home (H), "localhost" is W)
Some explanation: as in the question, my situation was:
H -------------------> S not working ( ssh -L 8001:S:8001 user#S from H)
H W -------> S working ( ssh -L 8001:S:8001 user#S from W)
home work server
While reversing like this:
H <------- W S ssh -R 8001:localhost:8001 user#W (from H)
H W <------- S ssh -L 8001:localhost:8001 user#W (from S)
home work server
did the trick. In other words, whatever is written on S:8001, is forwarded to W:8001, and whatever in turn is written to W:8001, is forwarded to H:8001, where my eclipse JVM is listening.
The tomcat JVM on S should be started with server=n, with arguments:
-agentlib:jdwp=transport=dt_socket,server=n,suspend=n,address=8001
Related
I'm trying to connect to a jmx port remotely but I can't seem to connect to it even though the port is open. Its a java process running in a container on a server thats a Nomad worker. Its running on 29406.
Here is what netstat shows:
netstat -tulpn | grep 29406
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 10.137.2.166:29406 0.0.0.0:* LISTEN -
udp 0 0 10.137.2.166:29406 0.0.0.0:* -
And this is whats in /etc/hosts
cat /etc/hosts
127.0.0.1 localhost
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
I've downloaded jmxterm on the server to try and connect to it, and noticed an interesting behavior. When I try using localhost to connect to the port, I get this:
#RuntimeIOException: Runtime IO exception: Failed to retrieve RMIServer stub: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: localhost; nested exception is:
java.net.ConnectException: Connection refused (Connection refused)]
When I use its own IP address, it then seems to work:
$>open 10.137.2.166:29406
#Connection to 10.137.2.166:29406 is opened
$>
Curious to understand why localhost doesn't work when I'm running this on the server itself...
The only way I've gotten jconsole (running on my laptop) to connect to it is by using an ssh tunnel like this:
ssh -Nf -D 7777 10.137.2.166
jconsole -J-DsocksProxyHost=localhost -J-DsocksProxyPort=7777 service:jmx:rmi:///jndi/rmi://10.137.2.166:29406/jmxrmi -J-DsocksNonProxyHosts=
I feel like I should be able to connect to it without creating a tunnel but unsure why I can't. If I run telnet locally from my laptop to the host, the connection does seem to open...
telnet 10.137.2.166 29406
Trying 10.137.2.166...
Connected to 10.137.2.166.
Escape character is '^]'.
To successful JMX handshake
the jmx server should be available by a host name outside (should also be declared on server jvm via java.rmi.server.hostname system property)
in addition to one open port (can be explicitly declared via com.sun.management.jmxremote.rmi.port jvm property) the jmx server chooses random another that's used for new jmx connection. It's quite problematic because you can't foresee particular port in order to exclude it from server's firewall restrictions, so the tunneling is necessary.
Server listened at only 10.137.2.166.
When you trying to create new socket with localhost domain, your application tying to establish 127.0.0.1 adress but your application not listening at this ip.
If you want to connect with localhost domain you have few options for solving.
Change your server configuration to listen on 127.0.0.1 and 10.137.2.166 at same time.
Change your server configuration to listen on 0.0.0.0 .
Listening at 0.0.0.0 its not recommended for security reasons .
Use iptables to forward port. Requires root privileges.
sysctl net.ipv4.ip_forward=1
iptables -t nat -A PREROUTING -p tcp -i lo --dport 29406 -j DNAT --to-destination 10.137.2.166:29406
iptables -A FORWARD -p tcp -d 10.137.2.166 --dport 29406 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
if you don't have root privileges you can use socat.
socat TCP-LISTEN:29406,fork,bind=127.0.0.1 TCP:10.137.2.166:29406
I only used jmx for visualvm connection and in this case they are two ports required to be available:
com.sun.management.jmxremote.port=9010
com.sun.management.jmxremote.rmi.port=9011
Also the java.rmi.server.hostname need to be set accordingly to the right network interface as the port will be bound only on that interface.
Once the ports are available from your client, you can use the jmx connection on the jmxremote.port port.
I try configure jmx according this instruction: http://activemq.apache.org/jmx.html
On localhost all works well. But when i try connect to FreeBSD server over VPN jconsole can't establish connection.
I use such settings for ACTIVEMQ_SUNJMX_START variable:
ACTIVEMQ_SUNJMX_START="
-Dcom.sun.management.jmxremote.port=1616
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.password.file=${ACTIVEMQ_BASE}/conf/jmx.password
-Dcom.sun.management.jmxremote.access.file=${ACTIVEMQ_BASE}/conf/jmx.access
-Djava.rmi.server.hostname=vpn_id_address
-Dcom.sun.management.jmxremote.local.only=false"
What i do wrong?
Confirm the port is listening, using netstat or other tool.
netstat -na | grep 1616
... should show an entry as LISTENING
Try to telnet to the port and send garbage. The server will disconnect you
$ telnet localhost 1099
Trying ::1...
Connected to localhost.
Escape character is '^]'.
garbage
Connection closed by foreign host.
There are a million other reasons why it may not be working. Firewall settings on the server, VPN port mapping, etc.. etc.. Until #1 and #2 are confirmed there isn't anything else to go on.
open command prompt/terminal then type: jconsole
then your jconsole will open and connect to activemq from it
service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi
I need to debug my app remotely, but I unable to do that, due to the following error:
Unable to open debugger port (X.X.X.X:8000): java.net.ConnectException "Connection timed out: connect"
I have:
Java app running in Tomcat on a remote server (Debian)
IntelliJ Idea running locally (Windows)
I came to the conclusion that cause of problem is that port 8000, used for remote debugging, is inaccessible via external ip, only via 'localhost'. Following are causes, why I think so:
A remote debug is working on an expected port:
root#victor-app-server:/opt/tomcat-home/bin# netstat -tulpn | grep 8000
tcp 0 0 0.0.0.0:8000 0.0.0.0:* LISTEN 3773/java
I able to telnet to it via 'localhost':
root#victor-app-server:/opt/tomcat-home/bin# telnet localhost 8000
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Connection closed by foreign host.
But unable to telnet via external ip:
root#victor-app-server:/opt/tomcat-home/bin# telnet X.X.X.X 8000
Trying X.X.X.X...
telnet: Unable to connect to remote host: Connection timed out
Here is output of iptables:
root#victor-app-server:/opt/tomcat-home/bin# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
How can I fix this issue with 8000 port? Or maybe there is other cause to my main problem?
This is the command that did the trick for me:
sudo ufw allow <debug_port>
I had a same problem via Java 11 and address property such as these JVM arguments:
-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=6565
However my problem is solved by change value of address property like this sample:
-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=*:6565
Now 6565 port is accessible externally.
Try "iptables -F" which unblocks the firewalls
I am trying to profile remote JVM using VisualVM. I have a remote production ubuntu machine on which my Java application is running and that's what I need to profile. I was following this tutorial to profile a remote server.
I started jstatd on my ubuntu production machine like this -
root#productionMachineA:/home/david# /usr/lib/jvm/java-1.7.0-openjdk-amd64/bin/jstatd -J-Djava.security.policy=permissions.txt -J-Djava.rmi.server.hostname=100.41.76.19 -J-Djava.rmi.server.logCalls=true -J-Djava.net.preferIPv4Stack=true
Here 100.41.76.19 is the IP Address of my production ubuntu machine. After starting jstatd on the ubunut machine, I did -
netstat -nlp | grep jstatd
And I can see this -
root#productionMachineA:~$ netstat -nlp | grep jstatd
tcp 0 0 0.0.0.0:1099 0.0.0.0:* LISTEN 32103/jstatd
tcp 0 0 0.0.0.0:60707 0.0.0.0:* LISTEN 32103/jstatd
which looks to me jstatd is running fine I guess. Now I opened VisualVM on my desktop, right click on Remote and select Add Remote Host, and finally type the IP address of the production machineA. And afterwards I don't see anything happening on VisualVM which makes me think something is wrong for sure.
Can anyone tell me what's wrong and what are the things I should try on? If anyone can provide steps by steps what I am supposed to do then it will be of great help.
Update:-
After adding port 1099 on my remote connection.
I got this error. Cannot connect to 100.41.76.19 using service:jmx:rmi.....
From my local desktop, I tried telnet on remote machine on port 1099 and this is what I got -
david#localDesktop ~
$ telnet 100.41.76.19 1099
david#localDesktop ~
$
I'm working on a Java 10 application that uses an embedded Jetty server to provide control from a local network, and I'm attempting to connect to the JVM and failing. It's running on Ubuntu 18.04 LTS desktop.
My startup script has the following lines:
java -Xdebug -agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=n -Djava.library_path=${LIB_PATH} -classpath ${CP} -jar ${APP_DIR}/app.jar
I have ufw on the system, and I've verified that the port is open. My output from ufw status includes:
8000 ALLOW Anywhere
8000 (v6) ALLOW Anywhere
In IntelliJ, my debug configuration is
-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:8000
When I try to connect, I get an error message that the connection is refused.
with the IP of the machine in the config's address box.
Looking at the output of netstat -l, I see the following:
tcp 0 0 localhost:8000 0.0.0.0:* LISTEN
Does this mean that the debugger is only listening for connection on the localhost? Do I need to do something to have it listen on a network?
So I found the answer fairly quick. I needed to modify the line I use for the server so that it reads:
java -Xdebug -agentlib:jdwp=transport=dt_socket,address=*:8000,server=y,suspend=n -Djava.library_path=${LIB_PATH} -classpath ${CP} -jar ${APP_DIR}/app.jar
So that is listens on all interfaces.