JMS client behind a firewall

I am using OpenJMS 7.6.1 and have developed several applications that 
use OpenJMS to interchange messages.
Within a local area network everything works fine, but when a client is 
behind a firewall  it does not receive any messages from the OpenJMS server.
I am using Tomcat running on port 8080 and HTTP connector for OpenJMS.
I have checked that there are several connection tryals from the server 
to ports 43xx in the client, that are blocked by the client firewall.
Is there any possibility of avoiding these server-to-client connections 
thus allowing communication to clients behind a firewall?

Thanks in advance

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