The discovery process allows applications to find other applications on the network and then discover how to connect to them. Note that this discussion builds on the discovery related concepts defined in OPC 10000-4. Discoverable applications are generally Servers, however, some Clientswill support reverse connections as described in OPC 10000-6and want Serversto be able to discover them.

Clientsand Serverscan be on the same host, on different hosts in the same subnet, or even on completely different locations in an administrative domain. The following clauses describe the different configurations and how discovery can be accomplished.

The mechanisms for Clientsto discover Serversare specified in 4.3.

The mechanisms for Serversto make themselves discoverable are specified in 4.2.

The Discovery Servicesare specified in OPC 10000-4. They are implemented by individual Serversand by dedicated DiscoveryServers. The following dedicated DiscoveryServersprovide a way for applications to discover registered OPC UA applications in different situations:

LDS and LDS-ME are specified in Clause 5. The GDS is specified in Clause 6.