The Modbus slave from the FAQ Modbus Communikation Master/Slave via Ethernet is used here.
Insert an Ethernet adapter in the device tree and specify the interface to be used.
If a target system is not defined yet, then the error message "Gateway not configured" is displayed.
Insert a Modbus TCP Master below the Ethernet adapter in the device tree.
Insert a Modbus TCP Slave below the Modbus TCP Master in the device tree.
Insert it in the Modbus Slave Channel tab and set the properties as follows:
Adapt the POU PLC_PRG as follows: