Does anyone even use JBoss on a WinXP 'server' behind a firewall?
If so, do you also use RMI or something else?
XP as a production server? Probably (hopefully?) not because the Windows XP EULA does not allow it - the EULA permits a maximum of 10 inbound connections. Though I image the are some running on Windows Server 2003/2008.
Regarding the port issue, I think that the RMI port is sort of a centralized control, and when a client connect a custom port for that client is negotiated. (Please take the previous statement with a grain of salt; I am by no means a networking expert and am simply attempting to explain mostly to myself the behavior I have seen.)
I have JBoss Portal + AS running on XP IA32, Server2003 X64, and Server2003 IA32. I forget why at the moment but I altered the port number in jboss-server for both RMI and JNDI from 1098 and 1099 to 10098 and 10099. I believe there was a port conflict for some other MS service, I'm pretty sure it was 1099 JNDI though, not 1098.
I found the details in my notes, it should be "obvious" it is a conflict with WINS services and WINS replication and it is both ports 1098 and 1099.