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tutorial_server_events.c
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/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
* See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */
#include "open62541.h"
#include <signal.h>
/**
* Generating events
* -----------------
* To make sense of the many things going on in a server, monitoring items can be useful. Though in many cases, data
* change does not convey enough information to be the optimal solution. Events can be generated at any time,
* hold a lot of information and can be filtered so the client only receives the specific attributes he is interested in.
*
* Emitting events by calling methods
* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
* The following example will be based on the server method tutorial. We will be
* creating a method node which generates an event from the server node.
*
* The event we want to generate should be very simple. Since the `BaseEventType` is abstract,
* we will have to create our own event type. `EventTypes` are saved internally as `ObjectTypes`,
* so add the type as you would a new `ObjectType`. */
static UA_NodeId eventType;
static UA_StatusCode
addNewEventType(UA_Server *server) {
UA_ObjectTypeAttributes attr = UA_ObjectTypeAttributes_default;
attr.displayName = UA_LOCALIZEDTEXT("en-US", "SimpleEventType");
attr.description = UA_LOCALIZEDTEXT("en-US", "The simple event type we created");
return UA_Server_addObjectTypeNode(server, UA_NODEID_NULL,
UA_NODEID_NUMERIC(0, UA_NS0ID_BASEEVENTTYPE),
UA_NODEID_NUMERIC(0, UA_NS0ID_HASSUBTYPE),
UA_QUALIFIEDNAME(0, "SimpleEventType"),
attr, NULL, &eventType);
}
/**
* Setting up an event
* ^^^^^^^^^^^^^^^^^^^
* In order to set up the event, we can first use ``UA_Server_createEvent`` to give us a node representation of the event.
* All we need for this is our `EventType`. Once we have our event node, which is saved internally as an `ObjectNode`,
* we can define the attributes the event has the same way we would define the attributes of an object node. It is not
* necessary to define the attributes `EventId`, `ReceiveTime`, `SourceNode` or `EventType` since these are set
* automatically by the server. In this example, we will be setting the fields 'Message' and 'Severity' in addition
* to `Time` which is needed to make the example UaExpert compliant.
*/
static UA_StatusCode
setUpEvent(UA_Server *server, UA_NodeId *outId) {
UA_StatusCode retval = UA_Server_createEvent(server, eventType, outId);
if (retval != UA_STATUSCODE_GOOD) {
UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_SERVER,
"createEvent failed. StatusCode %s", UA_StatusCode_name(retval));
return retval;
}
/* Set the Event Attributes */
/* Setting the Time is required or else the event will not show up in UAExpert! */
UA_DateTime eventTime = UA_DateTime_now();
UA_Server_writeObjectProperty_scalar(server, *outId, UA_QUALIFIEDNAME(0, "Time"),
&eventTime, &UA_TYPES[UA_TYPES_DATETIME]);
UA_UInt16 eventSeverity = 100;
UA_Server_writeObjectProperty_scalar(server, *outId, UA_QUALIFIEDNAME(0, "Severity"),
&eventSeverity, &UA_TYPES[UA_TYPES_UINT16]);
UA_LocalizedText eventMessage = UA_LOCALIZEDTEXT("en-US", "An event has been generated.");
UA_Server_writeObjectProperty_scalar(server, *outId, UA_QUALIFIEDNAME(0, "Message"),
&eventMessage, &UA_TYPES[UA_TYPES_LOCALIZEDTEXT]);
UA_String eventSourceName = UA_STRING("Server");
UA_Server_writeObjectProperty_scalar(server, *outId, UA_QUALIFIEDNAME(0, "SourceName"),
&eventSourceName, &UA_TYPES[UA_TYPES_STRING]);
return UA_STATUSCODE_GOOD;
}
/**
* Triggering an event
* ^^^^^^^^^^^^^^^^^^^
* First a node representing an event is generated using ``setUpEvent``. Once our event is good to go, we specify
* a node which emits the event - in this case the server node. We can use ``UA_Server_triggerEvent`` to trigger our
* event onto said node. Passing ``NULL`` as the second-last argument means we will not receive the `EventId`.
* The last boolean argument states whether the node should be deleted. */
static UA_StatusCode
generateEventMethodCallback(UA_Server *server,
const UA_NodeId *sessionId, void *sessionHandle,
const UA_NodeId *methodId, void *methodContext,
const UA_NodeId *objectId, void *objectContext,
size_t inputSize, const UA_Variant *input,
size_t outputSize, UA_Variant *output) {
UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Creating event");
/* set up event */
UA_NodeId eventNodeId;
UA_StatusCode retval = setUpEvent(server, &eventNodeId);
if(retval != UA_STATUSCODE_GOOD) {
UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
"Creating event failed. StatusCode %s", UA_StatusCode_name(retval));
return retval;
}
retval = UA_Server_triggerEvent(server, eventNodeId,
UA_NODEID_NUMERIC(0, UA_NS0ID_SERVER),
NULL, UA_TRUE);
if(retval != UA_STATUSCODE_GOOD)
UA_LOG_WARNING(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
"Triggering event failed. StatusCode %s", UA_StatusCode_name(retval));
return retval;
}
/**
* Now, all that is left to do is to create a method node which uses our callback. We do not
* require any input and as output we will be using the `EventId` we receive from ``triggerEvent``. The `EventId` is
* generated by the server internally and is a random unique ID which identifies that specific event.
*
* This method node will be added to a basic server setup.
*/
static void
addGenerateEventMethod(UA_Server *server) {
UA_MethodAttributes generateAttr = UA_MethodAttributes_default;
generateAttr.description = UA_LOCALIZEDTEXT("en-US","Generate an event.");
generateAttr.displayName = UA_LOCALIZEDTEXT("en-US","Generate Event");
generateAttr.executable = true;
generateAttr.userExecutable = true;
UA_Server_addMethodNode(server, UA_NODEID_NUMERIC(1, 62541),
UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
UA_NODEID_NUMERIC(0, UA_NS0ID_HASORDEREDCOMPONENT),
UA_QUALIFIEDNAME(1, "Generate Event"),
generateAttr, &generateEventMethodCallback,
0, NULL, 0, NULL, NULL, NULL);
}
/** It follows the main server code, making use of the above definitions. */
UA_Boolean running = true;
static void stopHandler(int sig) {
running = false;
}
int main (void) {
/* default server values */
signal(SIGINT, stopHandler);
signal(SIGTERM, stopHandler);
UA_ServerConfig *config = UA_ServerConfig_new_default();
UA_Server *server = UA_Server_new(config);
addNewEventType(server);
addGenerateEventMethod(server);
/* return value */
UA_StatusCode retval = UA_Server_run(server, &running);
UA_Server_delete(server);
UA_ServerConfig_delete(config);
return (int) retval;
}