Are the two JVM instances making confusion to remotely debug - java

To remotely debug my application running in tomcat7 over ubuntu server I set the following variables;
export CATALINA_HOME=/usr/share/tomcat7
export CATALINA_BASE=/var/lib/tomcat7/
export JPDA_ADDRESS=8090
export JRE_HOME=/usr/lib/jvm/java-1.7.0-openjdk-amd64
then I went to tomcat home folder /usr/share/tomcat7/bin and write the following line to run tomcat in debug mode.
\#./catalina.sh jpda start
then I try to remotely connect, I got Connection Refused. I checked with netstat -ln both 80 and 8090 ports were listening, then I stop tomcat using service tomcat7 stop , then my 80 port stops listening and I was able to remotely connect as well.
As a learner I need to know what is the reason of this? Is that something like 2 jvm started one with debugger and one simple and doing some confusion ? but I have it on another port why I am unable to connect to that?

Related

apache tomcat7 throws error after starting server

when I am adding server in eclipse and run getting error like "Several ports (8005, 8080, 8009) required by Tomcat v7.0 Server at localhost are already in use. The server may already be running in another process, or a system process may be using the port. To start this server you will need to stop the other process or change the port number(s)." and also changed port number in sever.xml to 8080 to 8085 but still getting the same error and still localhost:8080 showing welcome page.
Plase help me on this issue.
That means some of ports (8005, 8080, 8009) is already use by some other process. to solve this problem you have to stop that process or you can change your tomcat ports to other port like 8090,8091, 8092 etc.
for ubuntu :-
command for check process and ports : sudo netstat -tupln
kill process :- kill -9 4469

Unable to open debugger port through IntelliJ

I've got a server running on DigitalOcean and a JAR file that I want to debug. I first start the JAR on the remote server using
java -jar Server.jar -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005
but on the console I see no output like "listening on port 5005...".
When I press debug in IntelliJ it says
unable to open debugger port (198.xxx.xxx.xx:5005):
java.net.ConnectException "Connection refused"
This is my IntelliJ configuration:
I also tried using -Xdebug but it still didn't work.
If I set suspend=y it should wait until a debugger is connected, but instead, it starts without problems.
The command to start the remote Java process in debug mode looks correct. If you don't see "Listening to Port blah" when you start the server JAR, then it might mean that the debug args are not being picked up. Another way to quickly check this would be to test with a telnet localhost 5005 on the machine where the server JAR is being executed. The telnet will fail if that port is not being used.
I suggest that you try the following, since the order of the parameters might be significant (I'll add some official evidence for this later):
java "agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005" -jar Server.jar
this command worked for me:
export JAVA_OPTS='-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=0.0.0.0:5005'
by default idea remote dialog suggest:
'agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005'
change it to:
'agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=0.0.0.0:5005'
and issues port 5005.
This command worked for me:
java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005 -jar Server.jar
Thanks to suifengpiao14 but I'm going to describe the problem a bit more in detail.
I checked multiple things, and at the end found the reason: actually as like as a restful service we want to be accessible from out of the server we are running it that we should set 0.0.0.0 as the nameserver, here we should do a similar one.
I checked the difference between the server from which I can remotely debug and the one which I can't. using netstat command:
for the server which I was ok with:
tcp 0 0 0.0.0.0:5005 0.0.0.0:* LISTEN 8323/java
for the server which I had problem with:
tcp 0 0 127.0.0.1:5005 0.0.0.0:* LISTEN 8323/java
So, using below jvm options should be helpful:
'agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005'
'agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=0.0.0.0:5005'
In my case it was because under settings -> build, execution, deployment -> debugger I had a built in server running on the same port as which I was trying to attach my debugger to for some reason.
For people like me who sometimes forget to read...
Copy and paste the arguments to the command line when JVM is started
says the Run/Debug Configuration in IntelliJ, directly under:
-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005
Means:
Copy this line and go to your docker configuration. Add an environment variable (modify options dropdown). Paste it there with JAVA_OPTS= prepended.
Now when you did every correctly, you will have
Listening for transport dt_socket at address: 5005
and
Command line argument: -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005
This is who I solved it...
I've reproduced similar issue:
Unable to open debugger port (localhost:5005): java.net.ConnectException "Connection refused (Connection refused)"
I had it while running debugger w/ command line arguments for remote JVM using Run/Debug configurations:
-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005
by attaching IDE with exposed debug agent server.
Since I've used Kubernetes cluster, the reason was:
once the pod has been created and was running as expected, I needed to proceed to set up port forwarding with the kubectl port-forward command, with the port to expose locally for traffic from the application before running debugger.
Based on kubectl port-forward syntax:
kubectl port-forward <resource-type/resource-name> [local_port]:<pod_port>
In format like:
kubectl port-forward <pod-name> -n <namespace> 5005:5005
or in a shorter form:
kubectl port-forward <pod-name> 5005:5005
The client listens on port 5000 locally and forwards to 5000 in the
pod.
Accordingly entrypoint.sh file of the service was configured w/ the following command for Kubernetes cluster:
java -Djava.security.egd.=file:/dev/./urandom -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -Xmx400m -jar /service.jar
As result, running port-forward before debugger solved the issue.
One of the reason is that the port is not enabled. You can try by enabling the port using the below command
firewall-cmd --zone=public --permanent --add-port=8001/tcp
Once the port is up, restart tomcat & try connecting again.
Hope it helps.
This might help someone That port in JVM debug is not your web app port

Tomcat starts but home page cannot open with url http://localhost:8080

I am a newbie in Java, and I am trying to develop a web application.
I have Windows 7 32 bit. I have installed Java 7 and set the path and classpath as well. After that I installed Tomcat 7.
When I try to open tomcat home page using URL localhost:8080, it does not open and Tomcat stops automatically.
Please help me.
Make sure no other application using port 8080 before starting tomcat. If that's not the problem please paste tomcat log.
If you want to change tomcat's default port, go to tomcat folder and open conf folder, in which you can see server.xml. In that file you can see something like <Connector port= . Change the port value and start tomcat.
If you started tomcat through eclipse, It can be solved in different ways too.
Method 1:
Right click on server --> Properties
click on Switch location and apply.
Method2:
Double click in the server in eclipse.
Change Server location to Use tomcat installation(takes control of tomcat installation).
Your issue is not with port 8080, but with port 8005. Port 8005 is the shutdown port for Tomcat.
Rather than trying to figure out what is using port 8005, it may just be easier to edit TOMCAT_DIR/conf/server.xml and change the shutdown port to 8006
<Server port="8006" shutdown="SHUTDOWN">
For *Unix based systems, you can check the ports used by a particular application by issueing the following command in the terminal
[~/.]$ netstat -tuplen
You will get the list of all the ports that are being currently held and used by their respective process ID's
For windows user, type netstat -anin command prompt to see ports that are listening, this may come handy.
1) Using Terminal (On Linux), go to the apache-tomcat-directory/bin folder.
2) Type ./catalina.sh start
3) To stop Tomcat, type ./catalina.sh stop from the bin folder. For some reason ./startup.sh doesn't work sometimes.
For mac users
First Try : go to activity monitor -> search for java and kill the instance then restart the server and try.
Second Try:
Check log file for any errors under tomcat logs folder.
Use below command to check tomcat logs in terminal
tail -f {tomcatpath}/logs/catalina.out
Third Try:
Check if node or other apps using the same port. Use below command to check which app listening to a specific port. You will see list of apps with pid in second column.
lsof -i :8080 | grep LISTEN
Kill the process using below command
sudo kill -9 pid
If you are using eclipse to start the server then check for the server location being used and the deployment path:
In my case changing this to Tomcat installation instead of workspace metadata worked for me.
My issue has solved.I was getting log as below.
SEVERE: StandardServer.await: create[localhost:8005]:
java.net.BindException: Cannot assign requested address: JVM_Bind
My tomcat server was automatically stopping when I tried to open tomcat homepage with
URL.
So I just made some changes in windows->System32->drivers->etc->host file.
keep only 127.0.0.1 localhost and remove all other. your problem will be solved.
Thank you guys for your help :D
If you have your tomcat started (in linux check with ps -ef | grep java) and you see it opened the port 8080 or the one you configured in server.xml (check with netstat --tcp -na | grep <port number>) but you still cannot access it in your browser check the following:
It may start but with a delay of 3-5 minutes. Check the logs/catalina.out. You should see something like this when the server started completely.
INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 38442 msIf you don't have this INFO line your server startup is not complete yet. The problem may occur due to the SecureRandom class responsible to provide random Session IDs and which can cause big delays during startup.
Check more details and the solution here.
Check your firewall (on linux iptables -L -n): You can try to reset your firewall completely iptables -F if you are not into an exposed environment. However, pay attention, that leaves you without protection therefore it can be dangerous.
Check your selinux (if you are on linux).
These are some of the most forgotten and not obvious issues in having your Apache Tomcat up and running.
I am using Eclipse Java EE IDE for Web Developers. Version: Oxygen.1a Release (4.7.1a) in Windows 8.1 x64 with Apache Tomcat 8.5.24 (for testing purpose).
Port Name & Numbers for my Tomcat Server are :
Tomcat admin port : 8005
HTTP/1.1 : 8081 (my Tomcat Listening Port Number)
AJP/1.3 : 8009
Peoples, for those the Tomcat were running good earlier, and sometimes sudden after stopping tomcat server explicitly by pressing the below shown image button or may be other reasons.
Either they continuously failed to start/restart the tomcat with below said error:
Server Tomcat vX.Y Server at localhost failed to start.
or sometimes the Tomcat Server is started but instead of showing Tomcat Homepage in web browser, it is throwing client exception HTTP Status 404 – Not Found. in preferred web browser.
possibly, there are many reasons i.e. wrong Host name defined, Wrong Tomcat Server Locations defined in eclipse, project JDK/JRE version mismatch with Tomcat JRE dependent version, maven project version mismatch due to maven.compiler.source and maven.compiler.target version not defined under properties tag, mismatch version of project facet Dynamic Web Module to 2.5/3.0, Sometimes Tomcat Server is running on Windows Services level, previous stopped Tomcat port number were still listening and the processing pid were not killed in Tomcat defined timespan Timeouts Stop (in seconds): 15(by default) in eclipse and pid still running, failed to start in defined Start (in seconds): XX, etc.
Here I will give the resolution on, how to check and kill the running existing Tomcat port number's processing pid(beware, you must be aware with after effects).
In Windows, open you command prompt, and follow steps(my tomcat HTTP port is 8081):
netstat -ano | findstr :8081
TCP 0.0.0.0:8081 0.0.0.0:0 LISTENING 2284
TCP [::]:8081 [::]:0 LISTENING 2284
if any listening is being there, above command will list details of port listening along with processing pid at last of the line(here pid is 2284).
now kill the running pid like:
taskkill /PID 2284 /F
SUCCESS: The process with PID 2284 has been terminated.
also illustrated the above two steps like following:
Now, after resolving above illustrated reason, start the Tomcat Server.
I had the same issue. My tomcat was started but I was getting HTTP 404 page not found.However, in my situation, I installed tree instances of tomcat. Each instance contains conf, temp, work, webapps and logs folders. Unless I forgot, to copy the global web.xml under conf folder of each tomcat.
e.g: /opt/tomcat/mytomcatInstance/conf/web.xml
The web.xml Deployment Descriptor file describes how to deploy a web application in a servlet container.
So even if my tomcat was up, my web apps could not be deployed properly.
The problems may happen because of memory issue.
java.lang.OutOfMemoryError: Java heap space
please verify the logfile, any issues related to hardware(memory).
Look in TomcatDirectory/logs/catalina.out for the logs. If the logs are too long, delete the catalina.out file and rerun the app.
In my case, the port that tomcat was running on was defined in an application.properties file for 8000, not 8080. In my case, it looked like the same problem described here. Just leaving this here in case anyone has a similar setup and issue! :)

Connect to remote server and start/stop the Tomcat that's running on that particular server using Ant?

The purpose is to:
connect to a remote server maybe via host: ip , port: 8181
stop Tomcat that's running on that server
deploy a .war file
restart Tomcat
Underneath are few approaches I have taken so far to achieve this task:
Approaches taken so far:
I have looked at the following solutions but none of them worked for me:
http://www.linuxquestions.org/questions/linux-newbie-8/start-tomcat-server-remotely-824472/ --Not efficient
http://tomcat.apache.org/tomcat-6.0-doc/manager-howto.html#Start_an_Existing_Application
http://raibledesigns.com/wiki/Wiki.jsp?page=TomcatAntTasks
--only start/stop application not the actual tomcat itself
http://cargo.codehaus.org/Remote+Container
-- Which does't start/stop tomcat that's running on that server
If you have ssh access to the server, then you might like to consider the JSch library which you can use in combination with SSHExec Ant Task to start and stop your server:
<sshexec host="somehost"
username="dude"
password="yo"
command="/etc/init.d/tomcat restart"/>
For start/stop tomcat
In linux environment
use SSH to reach the terminal of the remote machine.
from the terminal You can start/stop the tomcat
to start startup.sh
to stop shutdown.sh
Under windows environment
Install OpenSSHD for Windows - this will allow remote "console" sessions.
If you looking for something very "unix-like" then you can install cygwin.
http://www.worldgoneweb.com/2011/installing-openssh-on-windows-7/
to start startup.bat
to stop shutdown.bat
For deployment
Simply go to tomcat manager link on the below page(on any environment)
http://your_server_ip:port_number/
user credential are specified in tomcat-users.xml inside conf di

java.net.BindException: Address already in use:8080

I am trying to run a Java webapp build instance but it stops in the middle of the build with this error:
java.net.BindException: Address already in use:8080
It's obviously trying to bind to the 8080 port but another process has already done so and wont share.
So, I checked to see what process is using the 8080 (netstat -anp | grep 8080). Apparently the jsvc.exec process is listening to my 8080 port. Upon checking (ps -fp) I find out that this is Tomcat (boostrap.jar).
So, to see if the build would at least complete, I killed the process. And yeah!! The Webapp build installed completely. But when I navigated my browser to localhost:8080 it says the service is not running - coz I killed Tomcat! I even tried localhost:8080/manager/list. Still said service not running.
So I restart Tomcat, checked localhost:8080 and Tomcat was back up. Checked localhost:8080/manager/list but did not see the Webapp instance I had just built.
What I am not getting here! My webapp wont build if I run tomcat (cant share 8080). And If i kill tomcat to complete the build, the webapp obviously cant run coz Tomcat is dead.
Please help me. Running Tomcat 5.5 in a LAMP environment on a remote server. NOTE: I am running a pre-built webapp build application (war) which I cant make changes to.
During a build? A build process usually doesn't require a port to be open. The issue is that two programs are attempting to use the same port. Without fixing the underlying issue, the immediate fix is to change the port Tomcat is running on. To change the port Tomcat runs on, edit install_dir/conf/server.xml and change the port attribute of the Connector element from 8080 to 8081.
If this is your first time running Confluence or you have recently added applications or made changes to the system, investigate what's running on port 8080.
If Confluence was not shut down properly, you can restart the machine or kill the process:
On Windows:
Hit Ctrl-alt-delete and look at open programs. Look for {{java.exe}}.
From a command window, run {{netstat -an}}. Check which ports are in use. You can identify which application is running this way, then close it from the Task Manager.

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