open62541/examples/client_connect_loop.c

/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
 * See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */

/**
 * Client disconnect handling
 * --------------------------
 * This example shows you how to handle a client disconnect, e.g., if the server
 * is shut down while the client is connected. You just need to call connect
 * again and the client will automatically reconnect.
 *
 * This example is very similar to the tutorial_client_firststeps.c
 */


#include "open62541.h"
#include <signal.h>

#ifdef _WIN32
# include <windows.h>
# define UA_sleep_ms(X) Sleep(X)
#else
# include <unistd.h>
# define UA_sleep_ms(X) usleep(X * 1000)
#endif

UA_Boolean running = true;
UA_Logger logger = UA_Log_Stdout;

static void stopHandler(int sign) {
    UA_LOG_INFO(logger, UA_LOGCATEGORY_CLIENT, "Received Ctrl-C");
    running = 0;
}

int main(void) {
    signal(SIGINT, stopHandler); /* catches ctrl-c */

    UA_ClientConfig config = UA_ClientConfig_default;
    /* default timeout is 5 seconds. Set it to 1 second here for demo */
    config.timeout = 1000;
    UA_Client *client = UA_Client_new(config);

    /* Read the value attribute of the node. UA_Client_readValueAttribute is a
     * wrapper for the raw read service available as UA_Client_Service_read. */
    UA_Variant value; /* Variants can hold scalar values and arrays of any type */
    UA_Variant_init(&value);

    /* Endless loop reading the server time */
    while (running) {
        /* if already connected, this will return GOOD and do nothing */
        /* if the connection is closed/errored, the connection will be reset and then reconnected */
        /* Alternatively you can also use UA_Client_getState to get the current state */
        UA_StatusCode retval = UA_Client_connect(client, "opc.tcp://localhost:4840");
        if (retval != UA_STATUSCODE_GOOD) {
            UA_LOG_ERROR(logger, UA_LOGCATEGORY_CLIENT, "Not connected. Retrying to connect in 1 second");
            /* The connect may timeout after 1 second (see above) or it may fail immediately on network errors */
            /* E.g. name resolution errors or unreachable network. Thus there should be a small sleep here */
            UA_sleep_ms(1000);
            continue;
        }

        /* NodeId of the variable holding the current time */
        const UA_NodeId nodeId =
                UA_NODEID_NUMERIC(0, UA_NS0ID_SERVER_SERVERSTATUS_CURRENTTIME);

        retval = UA_Client_readValueAttribute(client, nodeId, &value);
        if (retval == UA_STATUSCODE_BADCONNECTIONCLOSED) {
            UA_LOG_ERROR(logger, UA_LOGCATEGORY_CLIENT, "Connection was closed. Reconnecting ...");
            continue;
        }
        if (retval == UA_STATUSCODE_GOOD &&
            UA_Variant_hasScalarType(&value, &UA_TYPES[UA_TYPES_DATETIME])) {
            UA_DateTime raw_date = *(UA_DateTime *) value.data;
            UA_String string_date = UA_DateTime_toString(raw_date);
            UA_LOG_INFO(logger, UA_LOGCATEGORY_CLIENT, "string date is: %.*s", (int) string_date.length, string_date.data);
            UA_String_deleteMembers(&string_date);
        }
        UA_sleep_ms(1000);
    };

    /* Clean up */
    UA_Variant_deleteMembers(&value);
    UA_Client_delete(client); /* Disconnects the client internally */
    return UA_STATUSCODE_GOOD;
}