The OPC DataExchange server enables OPC Client applications to share data. Each OPC Client writes to the OPC DataExchange Server. Other OPC Client applications such as SCADA or HMI packages can read the data automatically. In this way, OPC Clients can pass data from one to the other. For example, a custom VB (Visual Basic) application can write to OPC DataExchange Server and an off-the-shelf SCADA system can automatically receive the OPC update.