An OPC Server is a software module that enables applications to provide their data to the outside world using OPC. OPC is based on client/server architecture.

Many OPC Servers are used strictly as “protocol converters.” In other words, they connect to an automation controller (such as a PLC, DCS, RTU, etc), using one communication protocol, and convert the data and calls to OPC. OPC Servers enable application to read and write data. They enable users to conduct supervisory control and data acquisition (SCADA).

Other OPC Servers are used to enable users to retrieve data from an HMI, Historian, Maintenance system, etc. In that sense, the OPC Server is used to expose the data from that application to the outside world in a standards-based manner.

OPC Servers can handle an unlimited number of OPC Client connections. In addition, OPC Servers can handle multiple OPC specifications simultaneously. An OPC Server can support OPC DA (Data Access), OPC HDA (Historical Data Access), OPC A&E (Alarms & Events), and even OPC UA (Unified Architecture) inside the same OPC Server.

See also: OPC Client, Server