An OPC UA Client wishing to connect to an OPC UA Server needs the address of the Server. UA Discovery defines the means to find OPC UA Servers, their supported protocols, security policies and other capabilities.
Discovery has to consider different configurations
- Client and Server on the same host
- on the same network or
- on completely different locations in a system (a plant, an enterprise).
Furthermore, Servers may be installed on different types of host devices like a sensor, a control device, or a workstation. A single device may host more than one Server.
Servers may have multiple endpoints if they support multiple addresses, protocols, or multiple levels of security. Clients can discover these endpoints and choose the proper one based on a system-wide policy or based on manual selection.
Note - Discovery is specified in OPC UA Part 12, the Discovery Services are specified in OPC UA Part 4