How to suscribe an application to pulse events?

[jlainez-asts]

Hi,
Using as a base the subscribe_to_events.c example, how can I subscribe an application to a recurring event? I supose I need to subscribe to tns1:UserAlarm/tnsaxis:Recurring/tnsaxis:Pulse, but I don't get how to adapt the sample.

Thanks!!

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[vivekatoffice]

Hi @jlainez-asts ,
I have used the AXIS Metadata Monitor to get the correct AXEventKeyValueSet.

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Code

/**
 * Copyright (C) 2021, Axis Communications AB, Lund, Sweden
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * - subscribe_to_event.c -
 *
 * This example illustrates how to setup an subscription to
 * an ONVIF event.
 *
 * Error handling has been omitted for the sake of brevity.
 */

#include <axsdk/axevent.h>
#include <glib-object.h>
#include <glib.h>
#include <syslog.h>

/**
 * brief Callback function which is called when event subscription is completed.
 *
 * This callback will be called when the subscription has been registered
 * with the event system. The event subscription can now be used for
 * subscribing to events.
 *
 * param subscription Subscription id.
 * param event Subscribed event.
 * param token Token as user data to the callback function.
 */
static void subscription_callback(guint subscription, AXEvent* event, guint* token) {
    const AXEventKeyValueSet* key_value_set;
    gchar *my_string ;

    // The subscription id is not used in this example
    (void)subscription;

    // The token is not used in this example
    (void)token;

    // Extract the AXEventKeyValueSet from the event
    key_value_set = ax_event_get_key_value_set(event);

    // Get the Value of the Processor Usage
    ax_event_key_value_set_get_string(key_value_set, "id", NULL, &my_string, NULL);

    // Print a helpful message
    syslog(LOG_INFO, "Received event with id: %s\n", my_string);
    g_free(my_string);
    /*
     * Free the received event, n.b. AXEventKeyValueSet should not be freed
     * since it's owned by the event system until unsubscribing
     */
    ax_event_free(event);
}

/**
 * brief Setup a subscription for an event.
 *
 * Initialize a subscription for AXEventKeyValueSet that matches
 * ProcessorUsage, which is using the ONVIF namespace "tns1".
 *
 * Topic: tns1:Monitoring/ProcessorUsage
 *
 * param handler Event handler.
 * param token Token as user data to the callback function.
 * return subscription id as integer.
 */
static guint onviftrigger_subscription(AXEventHandler* event_handler, guint* token) {
    AXEventKeyValueSet* key_value_set = NULL;
    guint subscription                = 0;

    key_value_set = ax_event_key_value_set_new();
    
    
    // Set keys and namespaces for the event to be subscribed
    // tns1:UserAlarm/tnsaxis:Recurring/Pulse
    ax_event_key_value_set_add_key_values(key_value_set,
        NULL,
        "topic0", "tns1", "UserAlarm", AX_VALUE_TYPE_STRING,
        "topic1", "tnsaxis", "Recurring", AX_VALUE_TYPE_STRING,
        "topic2", "tnsaxis", "Pulse", AX_VALUE_TYPE_STRING,
         "id", NULL,NULL, AX_VALUE_TYPE_STRING,
        NULL);

    /*
     * Time to setup the subscription. Use the "token" input argument as
     * input data to the callback function "subscription callback"
     */
    ax_event_handler_subscribe(event_handler,
                               key_value_set,
                               &subscription,
                               (AXSubscriptionCallback)subscription_callback,
                               token,
                               NULL);

    syslog(LOG_INFO, "And here's the token: %d", *token);

    // The key/value set is no longer needed
    ax_event_key_value_set_free(key_value_set);
    
    return subscription;
}

/**
 * brief Main function which subscribes for an event.
 */
int main(void) {
    GMainLoop* main_loop          = NULL;
    AXEventHandler* event_handler = NULL;
    guint subscription            = 0;
    guint token                   = 1234;

    // Set up the user logging to syslog
    openlog(NULL, LOG_PID, LOG_USER);
    syslog(LOG_INFO, "Started logging from subscribe event application");

    // Event handler
    event_handler = ax_event_handler_new();
    subscription  = onviftrigger_subscription(event_handler, &token);

    // Main loop
    main_loop = g_main_loop_new(NULL, FALSE);
    g_main_loop_run(main_loop);

    // Cleanup event handler
    ax_event_handler_unsubscribe(event_handler, subscription, NULL);
    ax_event_handler_free(event_handler);

    // Free g_main_loop
    g_main_loop_unref(main_loop);

    // Cleanup syslog
    closelog();

    return 0;
}

Reference

1. ax_event_subscription_example.c
2. subscribe_to_event
3. subscribe_to_events

Output

[jlainez-asts]

Hi @vivekatoffice
I'll give it a try this morning.
thanks for your help!