By default, communication between SharePoint servers and service applications within a farm takes place by using HTTP with a binding to TCP 32843. When you publish a service application, you can select either HTTP or HTTPS with the following bindings:
- HTTP binding: TCP 32843
- HTTPS binding: TCP 32844
You can change the protocol and port binding for each service application. On the Service Applications page in Central Administration, select the service application, and then click Publish.
Reference: Plan security hardening for SharePoint Server
This answer is semi-valid, as it only obfuscates HTTP-traffic to another TCP-port instead of disabling it. No documentation or practical experience exists on the question
how to disable HTTP for SharePoint service-communication?.
My idea: You could route the inter-farm-traffic to a separate pair of NICs and encapsulate them to a
inter-farm-VLAN on your network. This won't be a simple approach, as the number of internal and external WebService-calls in SharePoint is huge.