Add support to the Modbus TCP driver for redundant slaves, via primary and secondary hostnames. This should monitor the health of both connections, and automatically failover between the two based on which is healthy. The data read/written by the two hostnames are connected to the same data / PLC tags.

Devices with redundant Modbus slaves are not uncommon. One example is the Triconex safety PLC with redundant TCM comms cards. Another example is an Allen Bradley ControlLogix PLC with two Prosoft Modbus cards. It’s also common on GE/BH Mark VIe PLCs.