I have set the default port to 81
What operating system are you using? If you are running on Linux, are you running as root? Do you have a firewall, and if so, is port 81 open? When JBoss comes up, what port does it say it opened? You should see a line that looks like this:
13:42:56,437 INFO [Http11BaseProtocol] Starting Coyote HTTP/1.1 on http-0.0.0.0-8080
Are you getting an errors when JBoss starts?
I am using SUSE 9.3 and there is no errors.
When I change the default port to 80 it works.
I have no firewall between server and internet.
Do you have a firewall, such as iptables, running on the server? If you have not opened port 81 in iptables, it will not work.
Are you running SELinux? Can't recall if that is on SUSE (lately I am using Fedora) but SELinux can cause various issues if not properly configured.