Line debugging, sometimes called step debugging, is the process of using a tool to set breakpoints in your code to pause execution. When a breakpoint is hit, you are able to review the state of the application at that particular line and step through your code.
This setting in the ColdFusion Administrator enables line debugging in ColdFusion. We advise leaving this disabled in your production environment, and also if you do not intend to use line debugging.
The debugger server listens for commands from the ColdFusion Builder client on a random available port. This could be a problem if ColdFusion (and hence the debugger server) is behind a firewall. As a workaround, you can specify a fixed debugger server port number and allow this port through the firewall. To set a fixed debugger server port number, specify the following JVM argument on the Java and JVM page of the ColdFusion Administrator (or the appropriate place for your JEEE Application Server), replacing portNumber with the port you want to use. You can also edit this directly in the `jvm.config` file:
-DDEBUGGER_SERVER_PORT={portNumber} (where {portNumber} is the port you wish to use).
Using line debugging can be enormously helpful when trying to track down a stubborn issue in your code. To setup line debugging, you will need a copy of ColdFusion Builder. You can download a trial version here. Then, head over to the instructions for getting it configured here.