Hello @jake.lu

You can register for login stream to get an error callback whenever a RDMLogin failed. The error is in a status message and come to onStatusMsg(..) method. The example source code can be found in:

• example330__Login__Streaming in Elektron SDK Java package
• 330__Login__Streaming in Elektron SDK C++ package

The example result from example330__Login__Streaming:

Received Status. Item Handle: 1 Closure: null 
Item Name: jala 
Service Name: <not set> 
Item State: Closed / Suspect / Not entitled / 'jala, unknown to system.' 

You can create a custom log handler to get log messages, as mentioned in this site.

Then, you can use the following code to register your custom log handler.

LogManager.getLogManager().reset();
Logger rootLogger = LogManager.getLogManager().getLogger("");
rootLogger.setLevel(Level.FINEST);
rootLogger.addHandler(new MyLogHandler());