Using the shared memory send / recieve from inside an ndisplay config

I have two ndisplay configs in a level. They are the same setup.

What I need to do is send all the pixels from one and update the other.

There are settings for exactly this, it seems:

I have set one to be a shared memory sender, and one to be the receiver.

However, nothing happens.

Is there a trick to this?

How can i use the shared memory send / receive inside an ndiplay config, in editor?