Remote debug question

Hi, this is a question about remote debugging in IDEA 3.0.5, not about EAP. But I can't find a good place to ask this question, so here it is.

I tried to do the remote debug on IDEA to tomcat server 4.1.27. I started the tomcat server by adding the remote debug options. If the tomcat and idea are running on the same host, the remote debug connection connect successfully. I can step in, out, over on my servlet code without any problem. But if I started the tomocat on another host,(the same start up script), then configure the IDEA to connect to the host, it looks that the connection is fine, but all the breakpoints didn't work. Why is that?

OS: Both machines are window 2000 server
JDK: 1.4.2
IDEA: 3.0.5
Tomcat: 4.1.27

Question: if the remote debug can work on remote host (not the localhost), then my questions is that remote machine has its own all java compiled classes file. It is the same source code on both machine, but how the remote JVM can map the class java files info with the java source code on the client machine? I was told that remote debug can debug on the remote JVM. And I can't figure it out, Anything I did wrong?

Thanks