In d.3 config under Java/Groovy, activate the setting Java Remote Debugging (JAVA_REMOTE_DEBUGGING) to fix errors in Groovy code. If you activate the setting, the d.3 server processes start the Java Virtual Machine in debug mode. You can then connect to a d.3 server process via Remote Java Debugger to fix the errors in the Groovy hooks.

The port 43400 is used for communication. As each d.3 process starts its own Java Virtual Machine (JVM), the ports used are incremented, i.e. the first process started using JAVA_REMOTE_DEBUGGING opens port 43400, the second process opens port 43401 and so on. The ports appear when the JVM is started with the message Java Remote Debugging Port in the d.3 log.

Further information on the subject of debugging can be found in the usual technical literature and on the Internet.