I have a problem that I can not set up my application in debug mode with IntelliJ IDE, but run mode is OK.
My OS is Windows 7, IDE is IntelliJ IDEA, web container is Tom
I came in this scenario and as the above answers I tried to change the port like Edit Configuration -> Startup/Connection -> debug -> change the Port but it didn't solve my problem cause I was running my application in debug mode so once try to run the application as normal without debug. it solved my problem!