The little DebugView application from Microsoft can be very useful to see the debug messages from various applications. If you run it as admin on Windows and set the option in the menu to capture global Win32 messages, it will show the debug messages from our plugin used by FileMaker Server:
As you see MBS FileMaker Plugin on Server always prints this welcome line including version, platform, 32/64bit, which FileMaker process and the version of the FileMaker SDK reported by the loading FileMaker application.
If you use MBS("Trace") without a file path, you will see all calls to plugin functions in the log, too. This is very handy to have a live view on what's going on with the plugin. If you set the option to trace only errors with Trace.ErrorsOnly, you only see the calls which return an error message.