VScode Remote Debugging

VScode Remote Debugging | Generated by AI

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To perform remote debugging in Visual Studio Code (VSCode) for a WebSphere Liberty Server running in debug mode, you can use VSCode’s built-in Java debugging features. Below are the detailed steps to set this up without installing any WebSphere Liberty-specific plugins, assuming you have the standard Java Extension Pack (which includes the Debugger for Java) already installed.

Step 1: Start the WebSphere Liberty Server in Debug Mode

Open a terminal or command prompt.
Navigate to your WebSphere Liberty installation directory.
Run the following command to start your server in debug mode:
```
server debug default
```
- Replace default with your server’s name if it’s different.
The server will start with debugging enabled, typically listening on port 7777.
Check the server’s console output or logs for a message like:
```
Listening for transport dt_socket at address: 7777
```
- This confirms the debug port. If it’s a different port (e.g., due to a conflict), note the number displayed.

Step 2: Configure Remote Debugging in VSCode

Open Your Project in VSCode:
- Ensure your Java project (containing the source code deployed to the server) is open in VSCode. This allows the debugger to map breakpoints to the running code.
Access the Run and Debug View:
- Click the Run and Debug icon in the left sidebar (a play button with a bug) or press Ctrl+Shift+D (Windows/Linux) or Cmd+Shift+D (Mac).
Create or Edit the launch.json File:
- In the Run and Debug view, click the gear icon next to the configuration dropdown.
- If prompted to select an environment, choose Java. This creates a launch.json file in the .vscode folder of your workspace.
- If the file already exists, it will open for editing.
Add a Debug Configuration:
- In the launch.json file, ensure it contains a configuration for attaching to the remote JVM. Here’s an example:
```
{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "java",
            "name": "Attach to WebSphere Liberty",
            "request": "attach",
            "hostName": "localhost",
            "port": 7777
        }
    ]
}
```
- Explanation of Fields:
  - "type": "java": Specifies the Java debugger.
  - "name": "Attach to WebSphere Liberty": A descriptive name for this configuration.
  - "request": "attach": Indicates that VSCode will attach to an existing JVM process.
  - "hostName": "localhost": The hostname of the machine running the server. Use the server’s IP address or hostname if it’s on a different machine.
  - "port": 7777: The debug port from Step 1. Update this if the server is using a different port.
Save the File:
- Save the launch.json file after adding or editing the configuration.

Step 3: Start the Debugging Session

Ensure the Server is Running:
- Verify that the WebSphere Liberty Server is still running in debug mode from Step 1.
Select the Configuration:
- In the Run and Debug view, select “Attach to WebSphere Liberty” from the dropdown menu at the top.
Launch the Debugger:
- Click the green play button or press F5. VSCode will connect to the server’s JVM process.
Set Breakpoints:
- Open your Java source files in VSCode.
- Click in the gutter (left of the line numbers) to set breakpoints where you want execution to pause.
Interact with the Application:
- Use your application (e.g., send HTTP requests) to trigger the code paths with breakpoints. When a breakpoint is hit, VSCode will pause execution, allowing you to inspect variables, step through code, and debug.

Additional Notes

Local vs. Remote Server:
- If the server runs on a different machine, replace "localhost" with the server’s hostname or IP address in the launch.json file. Ensure the debug port is accessible through the network (e.g., not blocked by a firewall).
Debug Port Confirmation:
- If you’re unsure of the port, always check the server’s output after running server debug default. It will explicitly state the port it’s listening on.
Source Code Matching:
- The source code in VSCode must match the code running on the server for breakpoints to work correctly. Ensure your project is up-to-date and compiled with debug information (the default in most Java builds).
Server Behavior:
- With server debug default, the server starts immediately (not waiting for a debugger). You can attach VSCode at any time while it’s running.
Prerequisites:
- The Java Extension Pack (or at least the Debugger for Java extension) must be installed in VSCode. This is a standard tool for Java development and provides the necessary debugging capabilities.

By following these steps, you can effectively debug your WebSphere Liberty Server remotely using VSCode’s built-in features, without needing additional plugins specific to WebSphere.

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