Discovery allows Clients to find OPC UA Servers, their supported protocols, security policies and other capabilities. An OPC UA Client wishing to connect to an OPC UA Server needs the address of the Server. Client and Server can be on the same host, on the same network or even on completely different locations in a system (a plant, an enterprise). Servers may be installed on many different types of host devices like a sensor, a control device, or a workstation. A single device may host more than one Server.
The OPC UA discovery process allows Clients to find Servers on the network and then discover how to connect to them. The information required to connect is provided in the form of an endpoint. An
endpoint includes information about the address, the protocol to use, the manner to encode data and security level.
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