You can use set property method for changing the IP address of Ethernet Equipment keeping the parameter for this property as "CON_IPAddress". The methods to be used as follows:
int[] ipAddress = {192, 168, 1, 10};
ModbusEquipment01.openConfig();
ModbusEquipment01.setProperty("Con_IPAddress", ipAddress);
ModbusEquipment01.commitConfig();
Please take note that this is not limited to only Modbus TCP equipments but it can be used for all the Ethernet type Equipments.