Clarification for multiple clients with MAVProxy?

I’m slowly building my perfect GCS solution and at the moment, I’m looking at MAVProxy on an RPi3 as a central component. In my current planning, MAVProxy maintains the telemetry link to the UAS. I plan to build some switch modules as simulated joysticks with ATMEGA 32U4s and map the buttons to some actions, such as mode change, etc.
I have been doing some experiments with connecting multiple UDP clients to the MAVProxy. I noticed that if I connect multiple clients, e.g. 2 laptops with QGC, at the same time to the same UDP port, both report connection issues. If I use 2 different ports, they don’t.

So, just to be sure I don’t run into anything later - if I connect multiple UDP clients to one MAVProxy, what is the best (required) practice? One port per client? Different MAVLink IDs per client? Anything else?