'jdb' - The Java Debugger

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(Continued from previous part...)

The target application is launched in "shared memory server" mode. Its execution is suspended. Now open another command window and run:

>jdb -attach MyHello
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
>
VM Started: No frames on the current call stack

main[1] stop in Hello.main
Deferring breakpoint Hello.main.
It will be set after the class is loaded.

main[1] cont
> Set deferred breakpoint Hello.main

Breakpoint hit: "thread=main", Hello.main(), line=3 bci=0
3          System.out.println("Hello world!");

main[1] list
1    public class Hello {
2       public static void main(String[] a) {
3 =>       System.out.println("Hello world!");
4       }
5    }

main[1] cont
>
The application exited

As you can see, the debugger successfully connected to the target application. I used "next" command to let the target application to execute the current statement.

Let's try option #3 first. Open a command window on a windows system and run:

>java -agentlib:jdwp=transport=dt_socket,address=localhost:8888,server=y,
   suspend=y Hello

Listening for transport dt_socket at address: 8888

The target application is launched in "socket server" mode. Its execution is suspended. Now open another command window and run:

>jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=8888
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
>
VM Started: No frames on the current call stack

main[1] stop in Hello.main
Deferring breakpoint Hello.main.
It will be set after the class is loaded.

main[1] cont
> Set deferred breakpoint Hello.main

Breakpoint hit: "thread=main", Hello.main(), line=3 bci=0
3          System.out.println("Hello world!");

main[1] quite

Cool. I know how to run "jdb" to debug an application running on a remote machine now!

However, the command suggested in the JPDA documentation did not work:

>jdb -attach localhost:8888
java.io.IOException: shmemBase_attach failed: The system cannot find
   the file specified
        at com.sun.tools.jdi.SharedMemoryTransportService.attach0(...
        ...

My guess is that the Windows version of "jdb" assumes "shared memory" as the default transport mode.

(Continued on next part...)

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