How to debug with WAS 5.0

I'm not sure if I'm doing right or not. I'm trying to debug the application
running on WAS 5.0 but debug the source code in WSAD. I followed the WSAD infocenter's to set up the WAS in debug mode. I changed, one field startup checkbox in servers -> server1 -> configuration -> debugging service but keep the others as default. I'm confused now and it doesn't work. WSAD said "cannot attach to localhost:7777". It seems that WSAD is doing right, but what is wrong with WAS 5.0. How can I attach WSAD to WAS and debug the code running in WAS? What does the agent controller do for me?