Try the Admin Console for JBoss provided by Unisys. It has a page that lists all of the ports used by a particular instance of JBoss. It has been tested with 3.2.6, 3.2.7 and 4.0.2, on Windows and Linux.
You can download it from http://ecommunity.unisys.com. Click on the Java & J2EE hot link and then on the link for your platform.
Warning #1: Free registration to eCommunity is required.
Warning #2: You can download either the source or a binary distribution. The binary distribution catains several other softwares (including JBoss 3.2.6) which you may or may not want to install. The source distribution will compile successfully only against 3.2.6/7 (the apis changed in 4.0.2), but will run with 4.0.2.