Webshop in a DMZ

Greetings to all. I had Webshop running fine right up until I moved my webshop server into a DMZ Zone. Now my dispatcher message queues can not see the Webshop server which is the PEC for the message queues. I have re-installed the PEC controller on the webshop box since I did make a change of IP when I moved it. My problem is that when trying to re-install the IC portion of the message queues on the dispatcher it can not find the PEC and so can not continue the installation. Does anyone know if there are specific ports that need to be opened on the DMZ side in order to facilitate the communication between the two boxes or of anyway I can get them to talk to each other at all. Thanks for any input Eric (Frustrated) Watkins