You need to start the server in debug mode (rightclick at server, choose Debug instead of Start) and add breakpoints to the code. You can add breakpoints to the code by doubleclicking on the gray bar area at the left side from the code line. You'll get a blue dot there. When the JVM is about to process this line, then it will stop there until you take actions in the debug perspective (step into, step over, step return, next breakpoint).