opc source code

third_party/open62541/examples/tutorial_client_firststeps.c

@@ -0,0 +1,81 @@
+/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
+ * See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */
+
+/**
+ * Building a Simple Client
+ * ------------------------
+ * You should already have a basic server from the previous tutorials. open62541
+ * provides both a server- and clientside API, so creating a client is as easy as
+ * creating a server. Copy the following into a file `myClient.c`: */
+
+#include <open62541/client_config_default.h>
+#include <open62541/client_highlevel.h>
+#include <open62541/plugin/log_stdout.h>
+
+int main(void) {
+    UA_Client *client = UA_Client_new();
+    UA_ClientConfig_setDefault(UA_Client_getConfig(client));
+    UA_StatusCode retval = UA_Client_connect(client, "opc.tcp://localhost:4840");
+    if(retval != UA_STATUSCODE_GOOD) {
+        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
+                    "The connection failed with status code %s",
+                    UA_StatusCode_name(retval));
+        UA_Client_delete(client);
+        return 0;
+    }
+
+    /* 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);
+
+    /* 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_GOOD &&
+       UA_Variant_hasScalarType(&value, &UA_TYPES[UA_TYPES_DATETIME])) {
+        UA_DateTime raw_date = *(UA_DateTime *) value.data;
+        UA_DateTimeStruct dts = UA_DateTime_toStruct(raw_date);
+        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
+                    "date is: %u-%u-%u %u:%u:%u.%03u",
+                    dts.day, dts.month, dts.year, dts.hour,
+                    dts.min, dts.sec, dts.milliSec);
+    } else {
+        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
+                    "Reading the value failed with status code %s",
+                    UA_StatusCode_name(retval));
+    }
+
+    /* Clean up */
+    UA_Variant_clear(&value);
+    UA_Client_delete(client); /* Disconnects the client internally */
+    return 0;
+}
+
+/**
+ * Compilation is similar to the server example.
+ *
+ * .. code-block:: bash
+ *
+ *     $ gcc -std=c99 myClient.c -lopen62541 -o myClient
+ *
+ * In a MinGW environment, the Winsock library must be added.
+ *
+ * .. code-block:: bash
+ *
+ *    $ gcc -std=c99 myClient.c -lopen62541 -lws2_32 -o myClient.exe
+ *
+ * Further tasks
+ * ^^^^^^^^^^^^^
+ *
+ * - Try to connect to some other OPC UA server by changing
+ *   ``opc.tcp://localhost:4840`` to an appropriate address (remember that the
+ *   queried node is contained in any OPC UA server).
+ *
+ * - Try to set the value of the variable node (ns=1,i="the.answer") containing
+ *   an ``Int32`` from the example server (which is built in
+ *   :doc:`tutorial_server_firststeps`) using "UA_Client_write" function. The
+ *   example server needs some more modifications, i.e., changing request types.
+ *   The answer can be found in ``examples/client.c``. */