I can’t really help and have no suggestions, but my setup works ok and is:

I have my Raspberry Pi2 on port 80 (serving my web pages) and it is port 80 on my router.

My uRadMonitor is accessible on port 8080 externally using port forwarding on my router to port uRadMonitor port80.

I also have some other software on port 3837 port forwarded to port 3837 via my router too.

They all work together just fine. When I hadn’t redirected incoming 8080 traffic to the uRadMonitor it was still transmitting data to the uRadMonitor server just fine even though my RPi had port 80 tied up and was serving pages.

Normally only if someone wanted to view the uRadMonitor webpage or json data externally would they need to worry about port forwarding / router changes. Inernally the IP address should be just fine.

e.g. depending local network settings, and to view data locally, it shouldn’t affect uploads to servers by each device.

192.168.0.1 = router (port 80)
192.168.0.3 = RPi (port 80)
192.168.0.5 = Arduino (port 80)
192.168.0.9 = uRadmonitor (port 80)

Then using port forwarding rules in the router to access externally the addresses would be

my_fixed_IP = Rpi
my_fixed_IP:8080 = uRadMonitor
my_fixed_IP:3837 = Inverter Data