For queues, you can use standard QueueBrowser.
For topics I don't think there is any API.
Why you can't use mbeans ?
both messaging systems are in two different computer centers and I have only firewall access for jboss messaging to use bridges.
Maybe there is a way to use the naming service for mbean access?
If you have jndi access, the mbeans can be accessed through it, like:
please consult jboss doc for details.