Can devices send MQTT messages to Greengrass core on different port?

Hi,

I work in a convoluted corporate network environment where, for the time being, I have had to set up my Greengrass Core in a AWS VPC to test out IoT functionality. I have a KepServerEX environment on the internal network that I have set up as a thing in IoT and configured to send data to the Greengrass Core but traffic will not flow between device and core unless I can send it over port 443. Is there a way to configure the Core device to listen for MQTT messages on a port other than 8883? I have already configured it to talk to AWS IoT over 443 but I don't see similar configuration options for talking with devices.

Thanks for any help you can provide! If someone knows of a way to get AWS IoT to expose its core services inside of a VPC, that would be even better!