What is OPC UA ?
OPC-UA stands for OPC Unified Architecture. OPC-UA is the newest and fastest-growing OPC specification. It was designed to address some of the pitfalls of the OPC-DA specification (most notably the difficulty of establishing connections when the client and server are not running on the same computer) and has a service-oriented architecture.
OPC-UA servers provide services to OPC-UA clients, such as Read or Subscribe (ask the server to send updates when a value changes), where the clients can get the data they are looking for. The OPC-UA client must know the endpoint URL for the OPC-UA server, and the Node (called a “tag” in OPC-DA terminology) in that server that it wants the information from. With the OPC Data Client, it’s possible to read the value of a Node from an OPC-UA server with just two lines of code: