The SCADA Modbus OPC Server manufactured by MatrikonOPC allows connections to Modbus-compliant devices. An Advanced Polling Engine is installed in this server to poll all devices, and exclude the disconnected ones. Disconnected devices will be added back to the polling cycle once it goes back online. With this, delays when multiple devices under one communication channel may be prevented. It is also compatible with Windows Server 2008, and supports function 21 for Write Operations.