Client

Client is a network client that interacts with an OPC UA server via a collection of abstract Remote Procedure Calls (RPC), which is a request/response protocol. An RPC is initiated by the client, which sends a request message to the server. The OPC UA server then sends a response to the client, and the application continues its process. While the OPC UA server is processing the call, the OPC UA client is blocked (it waits until the server has finished processing before resuming execution), unless the OPC UA client operates in asynchronous callback mode.

The OPC UA client can operate in standard blocking socket call (default) or nonblocking cosocket mode. Blocking sockets must run in the context of a native thread, such as a thread running an LSP page. See Asynchronous Cosocket Mode for details.