Using the same instructions that are available for CFEclipse and CF8, I was able to get a debugger that works with CF9 and Eclipse 4.2 (Juno) with the CFEclipse plugin. After a long search, I found RDS configuration entries in the menu Window-> Preferences-> Adobe-> RDS Configuration. How I configured it:
You have to make sure that the port that starts the Debug RDS server is open: I use Windows Server 2008 and basically open the port to which I added the JVM Arguments parameters in the ColdFusion admin (otherwise Coldfusion starts it using some random port and it may be closed, which will mean that it does NOT accept incoming requests). syntax:
-server -Xdebug -Xrunjdwp: transport = dt_socket, server = y, suspend = n, address = 5005 -DDEBUGGER_SERVER_PORT = 49208
You will have to restart Coldfusion as this is used by the JVM at startup.
In the RDS configuration, I used the host name and port number of the application server, and not the Debug Server port itself. So in my case, I run IIS, which listens on port 80, so this is the host name and port number that I used.
Now a litmus test, if you can successfully connect, then check the debugger. If not, do not try to debug the application. In a related note, I am having some problems with breakpoints that sometimes don't hit, so this still bothers me as a production solution, but I might be doing something wrong too.
Of course, I curtailed it, but the fact is that it is apparently achievable. I am new to Coldfusion, so I know little about these options, but I just wanted to point out some of the configurations that, as soon as I enabled them, I was able to achieve linear debugging.