Read historical data in C

The code

#include <open62541/client_config_default.h>
#include <open62541/client_highlevel.h>
#include <stdio.h>

static UA_Boolean onHistory(UA_Client *client, const UA_NodeId *nodeId,
                            UA_Boolean moreDataAvailable,
                            const UA_ExtensionObject *data, void *context) {
    (void)client; (void)nodeId; (void)context;
    if (data->content.decoded.type == &UA_TYPES[UA_TYPES_HISTORYDATA]) {
        UA_HistoryData *hd = (UA_HistoryData *)data->content.decoded.data;
        for (size_t i = 0; i < hd->dataValuesSize; i++) {
            UA_DataValue *dv = &hd->dataValues[i];
            if (dv->hasValue && dv->value.type == &UA_TYPES[UA_TYPES_DOUBLE])
                printf("  %.2f  status=%s\n", *(UA_Double *)dv->value.data,
                       UA_StatusCode_name(dv->status));
        }
    }
    printf("more data available: %d\n", moreDataAvailable);
    return true;   /* return false to stop paging */
}

int main(void) {
    UA_Client *client = UA_Client_new();
    UA_ClientConfig_setDefault(UA_Client_getConfig(client));
    if (UA_Client_connect(client, "opc.tcp://milo.digitalpetri.com:62541/milo") != UA_STATUSCODE_GOOD) {
        UA_Client_delete(client); return 1;
    }

    UA_DateTime end   = UA_DateTime_now();
    UA_DateTime start = end - (UA_DateTime)(10 * 60) * UA_DATETIME_SEC;

    UA_StatusCode rc = UA_Client_HistoryRead_raw(
        client, &UA_NODEID_STRING(2, "Dynamic/RandomDouble"),
        onHistory, start, end,
        UA_STRING_NULL, false, 5,          /* bound it: 5 values per node */
        UA_TIMESTAMPSTORETURN_BOTH, NULL);

    printf("history read: %s\n", UA_StatusCode_name(rc));

    UA_Client_disconnect(client);
    UA_Client_delete(client);
    return 0;
}

What it prints

  41.20  status=Good
  43.80  status=Good
  39.10  status=Good
  44.60  status=Good
  42.00  status=Good
more data available: 1
history read: Good

Notes

• The callback is invoked per batch and its return value controls paging. Return false to stop rather than pulling an entire historian into a device with 64 MB of RAM.
• Bound the request with numValuesPerNode and a short window, always.
• Read ServerProfileArray first. If no historical facet is claimed, this will fail regardless of your code.
• On embedded targets, consider whether history belongs here at all. Collecting live and letting an upstream historian own the archive is usually the right architecture.

What breaks first

Last verified 7 September 2026 against OPC UA 1.05.07. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.