Is there any reason why a message can't be sent to an applet via JMS?
No. It all boils down to the standard applet limitations and your chosen implementation of JMS.
- An applet can connect only to the server it came from.
- An applet could be on the wrong side of several firewalls, so if your JMS implementation requires specific ports to be open, you might be facing some problems.
To get around the firewall issue, nothing could stop you from implementing a simple JMS client using HTTP stream (i.e. keep the connection open) to communicate with a servlet that would register on your async backbone. Soon, some commercial JMS implementation could implement it.