How to setup java remote debugging in eclipse?

How to setup java remote debugging in eclipse?

Remote debugging is not a new concept and many of you are aware of this just for who don’t know what is remote debugging? It’s a way of debugging any process could be Java or C++ running on some other location from your development machine. Since debugging is essential part of development and ability to debug your application not only saves time but also increase productivity. Local debugging is the best way in my opinion and should always be preferred over remote debugging but if local debugging is not possible and there is no way to debug your process then remote debugging is the solution.

Many of us work on a project which runs on Linux operating system and we do development mostly on Windows. Since I am working in Investment banking and finance domain I have seen use of Linux server for running electronic trading application quite a lot, which makes development difficult because you don't have code running on your development machine.

Some time we managed to run the project in windows itself which is essential for development and debugging purpose but many times its not possible due to various reason e.g. your project depends upon some of the platform dependent library or some Linux module whose windows version may not be available or your project is too big to run on windows and its heavily connected to upstream and downstream system its almost impossible to create same environment in your windows machine for development.
On such situation my approach to work is isolate the work I am doing and test that with the help of mock objects, Threads or by trying to run that module independently but this is also not a desired solution in some cases where you need to debug the project at run time to find out some subtle issues.

Eclipse provides us most useful feature called "Remote debugging" by using which you can debug your Linux running process from your windows machine. believe me this become absolutely necessary in some condition and knowing how to setup remote debugging and working of remote debugging in eclipse can greatly improve your productivity. In this Eclipse tutorial I will try to explain eclipse remote debugging or how to setup remote debugging in eclipse.

Now let's see how we can setup remote debugging in Eclipse:

1) First setup your java project in Eclipse.

2) Select your project, go to "Run" Menu option and select "Debug Configurations"

3) This will open Debug Configuration window select "Remote Java Application" icon on left side, Right click and say "New".4) After clicking on New, Eclipse will create Remote Java Application configuration for your selected project. Now next step is to setup host and port for remote debugging.

5) Now put the host name and port on which your process is listening for debugger in Linux machine. Check the "Allow termination of remote VM" check box if you would like to close java application running on Linux from eclipse.

6) Now you are all set to remote debug your project. but before starting to debug make sure your java process is started with java debug settings and listening on same host and port, otherwise eclipse will not able to connect successfully.

7) To debug just click the "Debug" button in last screen where we have setup host and port.

8) You can also debug by going to "Debug Configurations" selecting your project in "Remote Java Application” and clicking on "DEBUG".

Java remote debug setting and JVM debug options

In order to remote debug a java application, that application must be started with following JVM debug options:

java -Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y suspend=y -jar stockTradingGUI.jar

This will start java applicaiton stockTradingGUI into debug mode using Java Debug Wire Protocol (jdwp) protocol and it will listen on port 8001
suspend=y will ensure that that application will not start running until eclipse connect it on speicified debug port.It also important to note
That application must be start before eclipse tries to connect it other wise Eclipse will throw error "Failed to connect to remote VM. Connection refused" or "Connection refused: connect"

Enjoy remote debugging in Eclipse

Tip: In JVM DEBUG parameters there is a parameter called "suspend" which takes value as "y" or "n". so if you want to debug the process from start set this parameter as "suspend=y" and your Java application will wait until Eclipse remotely connect to it. Otherwise if you want to run your program and later want eclipse to be connected that set this as "suspend=n" so your java application will run normally and after eclipse remotely connected to it, it will stop on breakpoints.

Tip: Use start up script to put JVM debug parameter and use a variable e.g. isDebugEnabled and also REMOTE_DEBUG_PORT in the script export this variable when you want to remote debug your Java application. This will be very handy and will require just one time setup work.

Tip: if you get error "Failed to connect to remote VM. Connection refused" or "Connection refused: connect" then there might be two possibility one your java program is not running on remote host and other you are giving incorrect port or host name after verifying these two things if issue still persists then try giving full name of the host.

Tip: You also need to ensure that you run the same codebase in eclipse which is deployed in your remote machine so that what you debug and see in eclipse is true and real. you also need to ensure that your code is compile with debug option "-g" so that eclipse can easily gather debug info e.g. information about local variable. by default java only generate line numbers and source file information.with debug option -g your class file size might be more because it would contain some debug information.


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