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56 lines
2.2 KiB
C
56 lines
2.2 KiB
C
/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
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* See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */
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/**
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* Observing Attributes with Local MonitoredItems
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* ----------------------------------------------
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*
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* A client that is interested in the current value of a variable does not need
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* to regularly poll the variable. Instead, the client can use the Subscription
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* mechanism to be notified about changes.
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*
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* So-called MonitoredItems define which values (node attributes) and events the
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* client wants to monitor. Under the right conditions, a notification is
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* created and added to the Subscription. The notifications currently in the
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* queue are regularly sent to the client.
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*
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* The local user can add MonitoredItems as well. Locally, the MonitoredItems do
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* not go via a Subscription and each have an individual callback method and a
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* context pointer.
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*/
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#include <open62541/client_subscriptions.h>
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#include <open62541/server.h>
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#include <open62541/plugin/log_stdout.h>
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static void
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dataChangeNotificationCallback(UA_Server *server, UA_UInt32 monitoredItemId,
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void *monitoredItemContext, const UA_NodeId *nodeId,
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void *nodeContext, UA_UInt32 attributeId,
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const UA_DataValue *value) {
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UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Received Notification");
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}
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static void
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addMonitoredItemToCurrentTimeVariable(UA_Server *server) {
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UA_NodeId currentTimeNodeId = UA_NS0ID(SERVER_SERVERSTATUS_CURRENTTIME);
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UA_MonitoredItemCreateRequest monRequest =
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UA_MonitoredItemCreateRequest_default(currentTimeNodeId);
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monRequest.requestedParameters.samplingInterval = 100.0; /* 100 ms interval */
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UA_Server_createDataChangeMonitoredItem(server, UA_TIMESTAMPSTORETURN_SOURCE,
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monRequest, NULL,
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dataChangeNotificationCallback);
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}
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/** It follows the main server code, making use of the above definitions. */
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int main(void) {
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UA_Server *server = UA_Server_new();
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addMonitoredItemToCurrentTimeVariable(server);
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UA_Server_runUntilInterrupt(server);
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UA_Server_delete(server);
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return 0;
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}
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