Use Case: Let's take for example a set of Fronius SnapINverters in a daisy chain connection and let's try to control them through a Droplet. 

Firstly, we would only activate Modbus TCP Port 502 on the MASTER inverter.

(If you are not familiar with this setup, please refer to your OEM documentation. In this case, you would need to download the Fronius Datamanager Modbus TCP & RTU document and follow the instructions from page 72 onwards)

After the Master inverter is ready to communicate with your Droplet, follow this steps:
1) Connect your Fronius Smart meter to Fronius inverters as usual.
2) Connect your Fronius inverters in a daisy chain configuration.
3) Connect the MASTER inverter to the same network and subnet as the Droplet (Ethernet preferred/Wifi is fine as well)