We Keep Coding

How to connect remotely via tcp to the h2 database?

I am trying to start H2 in server mode to connect an application from another computer. But no matter how hard I have tried, I have not succeeded.
I have seen the documentation and to start the server from the command line is executed:
java -cp h2-2.1.214.jar org.h2.tools.Server -tcpAllowOthers
output:
TCP server running at tcp://127.0.1.1:9092 (others can connect)
PG server running at pg://127.0.1.1:5435 (only local connections)
Web Console server running at https://127.0.1.1:8082 (others can connect)
now from the other pc, as I understand I must execute the connection in the following way:
jdbc:h2:tcp://[server][:port]/[path]/[databaseName]
then it should be:
jdbc:h2:tcp://127.0.1.1:9092/home/mateo/database
But I have read that 127.0.1.1 only works locally. I have also noticed that when I open H2 Console in the examples I have seen, the machine's ip appears, that is to say: 192.168.X.
What am I doing wrong?
(Update)
I am currently using Linux.
I have launched the server from Windows and managed to connect it from Linux successfully following the above steps. But, I still don't understand why it doesn't work in Linux, in Windows it loads the server with the IP address of the machine. It makes me think that I have to do some additional configuration for Linux.
server running

You need to replace local IP address in your JDBC URL with real non-local IP address of your server (jdbc:h2:tcp://127.0.1.1:9092/*** -> jdbc:h2:tcp://192.168.1.4:9092/***, for example). H2 listens all network interfaces of the host, it doesn't matter which address was reported in “runnig at …” message.
You also may need to protect ports 8082 and 9092 from connections from untrusted systems if you have them in your internal network and from connections from external network (make sure your router or whatever you have doesn't redirect connections to the host with database server).

Profiling tomcat application with VisualVM

I am trying to run visualvm under the username tomcat6 because apparently visualvm can only find applications running under its username. So by default it is only finding applications running under my username. I have been able to connect visualvm with tomcat6 through jmx but that lacks the fine granularity of instrumented profiling.
I tried the following to run visualvm under the username tomcat6 but got the following error that I don't understand.
$ sudo -u tomcat6 jvisualvm
No protocol specified
Exception in thread "main" java.awt.AWTError: Can't connect to X11 window server using ':0' as the value of the DISPLAY variable.
at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
at sun.awt.X11GraphicsEnvironment.access$200(X11GraphicsEnvironment.java:65)
at sun.awt.X11GraphicsEnvironment$1.run(X11GraphicsEnvironment.java:115)
...

If the computer running your application is remote -- like a server -- then you can't run GUI applications without some work. It's probably going to be easier to enable remote access to VisualVM.
You can use two techniques to attach to a remote JVM: using jstatd or using JMX. I'm not sure what you think you are losing by using JMX, but evidently jstatd doesn't give you access to profiling tools, CPU monitor, etc.).
You need to configure your JVM and Tomcat to allow for remote access. That requires 3 steps:
Enable remote JMX. Turns out, there's a guide for that.
Fix the "wandering port" used for RMI. There's a guide for that, too.
(Optional) Arrange for secure remote-access to the server. The easiest way to do that would be to use ssh -Lport:localhost:port with a series of -L arguments to forward multiple ports from your workstation to your server. Map all the ports you had to configure in steps #1 and #2. If you don't do this, you'll need to have non-firewalled access to all the aforementioned ports.
Restart your JVM and connect with JVisualVM.
Update 2022-06-01
Note that the "wandering port" problem has been fixed at the JVM level, so there is no need for application (i.e. Tomcat) support for that. Item #1 for Tomcat 8.5 and later contains updated instructions making item #2 unnecessary with a recent JVM.

Unfortunately only sampling is available in remote mode so JMX will lack instrumentation tools.
Actually your approach to running visualvm under tomcat6 user is correct. You should take a look at this question on how to run X11 applications under sudo.
The easiest way to pass DISPLAY and XAUTHORITY environment variables is to use sudo -E command to preserve current user environment.
Also if you can't see your process under tomcat6 user you should check if CATALINA_TMPDIR is pointing to /tmp. Otherwise you should pass it to visualvm
jvisualvm -J-Djava.io.tmpdir="${CATALINA_TMPDIR}"
Actually there is a lot of alternatives like yourkit or jprofiler shipped with java agents which allows remote instrumentation profiling.

The easiest is to open a remote JXM port on Tomcat in order to be able to remotely (from your desktop computer) connect to your remote Tomcat (on your server) with jvisualvm.
You need to pass the following system properties to your JVM :
-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.port=<whatever_port_you_want>
-Dcom.sun.management.jmxremote.ssl=false
Then open jvisualvm on your local computer (JVM version needs to be the same or newer), File -> Add Remote Host -> Enter the name on the Host. It will create an entry for this host. Right lick on this Entry -> Add JMX connection -> Enter the port -> OK
jvisualvm will then be able to access remotely to your application.
You can also secure the connection if needed by using the following system properties (you need to create the files and locate them where you want :
-Dcom.sun.management.jmxremote.password.file=jmxremote.password
-Dcom.sun.management.jmxremote.access.file=jmxremote.access
These properties needs to be added to the CATALINA_OPTS environment variable. Fr exemple :
export CATALINA_OPTS = "$CATALINA_OPTS -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=8888 "
More info on JMX lies here : https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html

I tried to do something similar but I was not allowed to install JVisualVM on the server. Having JVisualVM connect to the remote machine never seemed to work correctly. I suspect firewall rules were blocking part of the the network connections.
The only way I found to remotely profile the server was via an ssh tunnel.
Set the JMX port in CATALINA_OPTS on the server
CATALINA_OPTS="$CATALINA_OPTS -Dcom.sun.management.jmxremote.port=13333 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false; export CATALINA_OPTS
On your desktop machine open an ssh connection to the server
ssh -D 61444 username#tomcat.server.address
Add a flag to JVisualVM so that it will proxy its network connection
"C:\Program Files\Java\jdk1.7.0_79\bin\jvisualvm.exe" -J-Dnetbeans.system_socks_proxy=localhost:61444 -J-Djava.net.useSystemProxies=true
Have JVisualVM connect to the jmxport and the network traffic is tunneled via ssh.
Good luck.

Unable to connect to remote JMX using VisualVM but OK with JConsole

I'm attempting to connect to a remote JMX service using VisualVM 1.3.8 with JRE 1.8.0. Making exactly the same connection with JConsole works perfectly, however the attempt to use the same parameters with VVM just hangs at the 'Adding services' stage. I've looked in the VVM log but there is literally nothing logged.
I also read here at the VVM remote JMX doc:
Note: To retrieve and display information on applications running on the remote host, the jstatd utility needs to be running on the remote host.
That puzzles me since I can make the remote JMX connection using JConsole and as far as I can tell, jstatd is not running on the remote.
Does anyone know if jstatd a requirement only for VVM as a remote JMX client? As the JMX connection can be made with JConsole between the same client and server endpoints, then there's no problem with network/firewall etc.
Other than that I'm really puzzled where else to look for clues?

I had the same trouble when I switched from Java 7 to 8, while using SOCKS where I was updating proxy settings through VisualVM -> Tools -> Plugins -> Settings -> Proxy Settings. However, I have been successful with the following:
Run your JVM with the following options:
-Dcom.sun.management.jmxremote.port=<JMX_PORT>
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.authenticate=false
Note that you could obviously do something more secure, both w.r.t SSL and authentication.
Setup a SOCKS proxy from your localhost to the remote server:
ssh -D<SOCKS_PORT> -vvv -N <REMOTE_HOST>
Run either of these commands on your localhost:
jconsole -J-DsocksProxyHost=localhost -J-DsocksProxyPort=<SOCKS_PORT> service:jmx:rmi:///jndi/rmi://<REMOTE_HOST:JMX_PORT>/jmxrmi
jvisualvm -J-DsocksProxyHost=localhost -J-DsocksProxyPort=<SOCKS_PORT> --openjmx <REMOTE_HOST>

jprofiler jpcontroller can't connect to jvm when called with host:port

i want to profile my web application now this is what i do:
run jpenable.exe and after it finds thi jvm, it gives me a port so i can connect to it using JProfiler GUI(for instance:12121)! now as I want to have commandline control i then try to connect jpcontroller using this command:
jpcontroller.exe localhost:12121
but it cannot connect and sticks there with no error! now if i use this command:
jpcontroller.exe <port>
then it works!
but actually i can't do this as i want to connect to a remote jvm!!
am i wrong some where?

jpcontroller does not connect to the port that is opened by the profiling agent, but it uses JMX to connect to the process. For that to work on a remote computer, add the VM parameter
-Djprofiler.jmxServerPort=[port]
to the profiled process and use that port in jpcontroller. Then, an MBean server will be created that listens on that port.

VisualVM through firewalls - RMI troubleshooting

Sorry for this question which must have been asked many times, but I can't succeed in resolving my problem.
I've read a lot of blogs, sites, forums, .... and didn't find any solution in my case.
Case :
I need to connect VisualVM on my box to distant servers (tomcats, weblogics) for performance / threads / memory monitoring.
Those servers are installed on (physical or virtual) machines which are protected by a firewall.
Large intervals of ports are open in the firewall and can be used, but not all ports.
Tests
I've tried direct connections through JMX in VisualVM, using following JVM options on the server-side at server startup :
-Djava.rmi.server.hostname=[hostname]
-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.port=[port]
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.authenticate=false
I've precised the hostname because from my network the hostname and the IP address of the server are not the same than those from the network of the remote server.
No success, VisualVM always seems searching for an unknown server.
tried starting jstatd on the server-side on a port accessible (-p option) from my box (telnet on this port works), but when launching visualVM on this host with the jstatd port, it still seems waiting for something unreachable.... Same behavior with jps connecting to this remote host.
tried using the same tools on a server with less network protection, and it works. So I have seen the connections between my box and the server and they are done on ports different from what I've specified to jstatd.
I understand that this port is needed for first communication (kind of handshake) and real communications are done on other ports, but not predictible (ex: 60305, 55197, ...).
Not sure I understand very well how RMI works.
Please, help me, I'm going crazy !

Unfortunately JMX tries to open ports other than the one you configure. Just yesterday I succeeded connecting to tomcat behind firewall via JMX. The two tricky parts are:
put a file called jmxremote.access in CATALINA_HOME/conf, which contains the following lines:
monitorRole readonly
controlRole readwrite
in server.xml set the ports that will be used by jmx, via a special tomcat listener (catalina-jmx-remote.jar required in /lib):
<Listener className="org.apache.catalina.mbeans.JmxRemoteLifecycleListener"
rmiRegistryPortPlatform="9009" rmiServerPortPlatform="9010" />
Then open these two ports on the firewall. It works. But that's just for tomcat.
Another option is to use ssh tunnelling. In short - you connect via SSH and configure it to forward some local port (where the jmx client is running) to some ports on the other side of the tunnel.
References:
Connecting to JMX on Tomcat 6 through a firewall
Connecting MySQL server on Amazon EC2 instance using ssh tunnel

Here are the steps to do this:
Launch an ejstatd in your remote host this way (in ejstatd folder): mvn exec:java -Djava.rmi.server.hostname=[remote_host_name] -Dexec.args="-pr 1099 -ph 1100 -pv 1101" (used for "jstatd" type connection)
Launch your Java application with those additional Java parameters: -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.port=1102 -Dcom.sun.management.jmxremote.rmi.port=1102 -Djava.rmi.server.hostname=[remote_host_name] (used for "JMX" type connection) (java.rmi.server.hostname is required here only because the IP and hostname from your network is not the same as the server point of view)
Open those 4 ports on your remote host and make them available to your local machine: 1099, 1100, 1101 and 1102
Launch JVisualVM
Right-click on "Remote" > "Add Remote Host..." and enter your remote host name in "Host name" (if you don't use the port 1099, you can change this in the "Advanced Settings")
Right-click on the remote host you've just created > "Add JMX Connection..." and enter "[remote_host_name]:1102" in "Connection" input, and check "Do not require SSL connection"
Your Java process will appear twice: one from the "jstatd" connection type, and one from the "JMX" connection type.
Disclaimer: I'm the author of the open source ejstatd tool.

On your [hostname], open up [port] and tcp port range 40000-60000 for your IP only.
This did the trick for me fairly well.