To start the Nexaweb Server in debug mode:
Click Run Nexaweb Server > Debug Nexaweb Server; or
Click the 
toolbar button.
This will start the Nexaweb Server in debug mode and switch the Studio to the Debug Perspective, allowing you to monitor all threads, variables, and the output console for the server. From here, you can open source code for your server-side logic, such as Servlet Java source files, and add breakpoints. See Adding Breakpoints for more information.