How do I configure the firewall to allow the connects from the internal server to the reverse invoke?

Why does the port change on the reverse invoke server (admin tool,security|ports|reverse invoke setting-> connections from the Servers, Host:port) everytime I re-register connections. Will that cause any problems?

Also, I have a test page that will http post an xml document to TN on my internal server, http://host:port/invoke/wm.tn/receive. but I now I want to test my reverse invoke server connections, by using a similar test page to submit my test xml document to the proxy port on the reverse invoke server, how do I configure the reverse invoke server to receive that xml document and foward it on to trading networks on the internal server. I have configured my proxy port for protocol = http, type = proxy, Package = WmRoot, enable = yes, Access Mode = allow by default, ip Access = allow by default
I have configured my Registration port for protocol = SOCK, Type = Registration, Package = WMRoot, enable =yes, Access Mode = allow by default, ip Access = allow by default. This is a development environment, so no firewall and allow by default is set for both access levels on both ports.