finished client first steps tutorial with reading nodes's values

doc/tutorial_firstStepsClient.rst

@@ -9,9 +9,9 @@ You should already have a basic server from the previous tutorial. open62541 pro
 
 As a recap, your directory structure should now look like this::
  
-  :myServerApp> rm *.o open62541.*
-  :myServerApp> ln -s ../open62541/build/*so ./
-  :myServerApp> tree
+  :myApp> rm *.o open62541.*
+  :myApp> ln -s ../open62541/build/*so ./
+  :myApp> tree
   .
   ├── include
   │   ├── logger_stdout.h
@@ -35,7 +35,7 @@ As a recap, your directory structure should now look like this::
 
 Note that I have linked the library into the folder to spare me the trouble of copying it every time I change/rebuild the stack.
 
-To create a really basic client, navigate back into the MyServerApp folder from the previous tutorial and create a client::
+To create a really basic client, navigate back into the myApp folder from the previous tutorial and create a client::
 
     #include <stdio.h>
 
@@ -59,7 +59,7 @@ To create a really basic client, navigate back into the MyServerApp folder from
 
 Let's recompile both server and client - if you feel up to it, you can create a Makefile for this procedure. I will show a final command line compile example and ommit the compilation directives in future examples.::
 
-    :myServerApp> gcc -Wl,-rpath=./ -L./ -I ./include -o myClient myClient.c  -lopen62541
+    :myApp> gcc -Wl,-rpath=./ -L./ -I ./include -o myClient myClient.c  -lopen62541
 
 We will also make a slight change to our server: We want it to exit cleanly when pressing ``CTRL+C``. We will add signal handler for SIGINT and SIGTERM to accomplish that to the server::
 
@@ -95,17 +95,17 @@ We will also make a slight change to our server: We want it to exit cleanly when
     }
 And then of course, recompile it::
 
-    :myServerApp> gcc -Wl,-rpath=./ -L./ -I ./include -o myServer myServer.c  -lopen62541
+    :myApp> gcc -Wl,-rpath=./ -L./ -I ./include -o myServer myServer.c  -lopen62541
 
 You can now start and background the server, run the client, and then terminate the server like so::
 
-    :myServerApp> ./myServer &
+    :myApp> ./myServer &
     [xx/yy/zz aa:bb:cc.dd.ee] info/communication	Listening on opc.tcp://localhost:16664
     [1] 2114
-    :myServerApp> ./myClient && killall myServer
+    :myApp> ./myClient && killall myServer
     Terminated
     [1]+  Done                    ./myServer
-    :myServerApp> 
+    :myApp> 
 
 Notice how the server received the SIGTERM signal from kill and exited cleany? We also used the return value of our client by inserting the ``&&``, so kill is only called after a clean client exit (``return 0``).
 
@@ -114,5 +114,157 @@ Asserting success/failure
 
 Almost all functions of the open62541 API will return a ``UA_StatusCode``, which in the C world would be represented by a ``unsigned int``. OPC UA defines large number of good and bad return codes represented by this number. The constant UA_STATUSCODE_GOOD is defined as 0 in ``include/ua_statuscodes.h`` along with many other return codes. It pays off to check the return code of your function calls, as we already did implicitly in the client.
 
+Minimalistic introduction to OPC UA nodes and node IDs
+-----------------------
+OPC UA nodespace model defines 9 standard attribute for every node:
 
++---------------+----------------+
+| Type          | Name           |
++===============+================+
+| NodeId        | nodeID         |
++---------------+----------------+
+| NodeClass     | nodeClass      |
++---------------+----------------+
+| QualifiedName | browseName     |
++---------------+----------------+
+| LocalizedText | displayName    |
++---------------+----------------+
+| LocalizedText | description    |
++---------------+----------------+
+| UInt32        | writeMask      |
++---------------+----------------+
+| UInt32        | userWriteMask  |
++---------------+----------------+
+| Int32         | referencesSize |
++---------------+----------------+
+|ReferenceNode[]| references     |
++---------------+----------------+
 
+Furthermore, there are different node types that are stored in NodeClass. 
+For different classes, nodes have additional properties.
+
+In this tutorial we are interested in one of these types: "Variable". In this case a node will have an additional attribute called "value" which we are going to read.
+
+Let us go on with node IDs. A node ID is a unique identifier in server's context. It is composed of two members:
+
++-------------+-----------------+---------------------------+
+| Type        | Name            | Notes                     |
++=============+=================+===========================+
+| UInt16      | namespaceIndex  |  Number of the namespace  |
++-------------+-----------------+---------------------------+
+| Union       | identifier      |  One idenifier of the     |
+|             |  * String       |  listed types             |
+|             |  * Integer      |                           |
+|             |  * GUID         |                           |
+|             |  * ByteString   |                           |
++-------------+-----------------+---------------------------+
+
+The first parameter is the number of node's namespace, the second one may be a numeric, a string or a GUID (Globally Unique ID) identifier. 
+
+Reading variable's node value
+-----------------------------
+
+In this example we are going to read node (n=0,i=2258), i.e. a node in namespace 0 with a numerical id 2258. This node is present in every server (since it is located in namespace 0) and contains server current time (encoded as UInt64).
+
+Let us extend the client with with an action reading node's value::
+
+    #include <stdio.h>
+
+    #include "ua_types.h"
+    #include "ua_server.h"
+    #include "logger_stdout.h"
+    #include "networklayer_tcp.h"
+
+    int main(void) {
+      //variable to store data
+      UA_DateTime raw_date = 0;
+
+      UA_ReadRequest rReq;
+      UA_ReadRequest_init(&rReq);
+      rReq.nodesToRead = UA_ReadValueId_new();
+      rReq.nodesToReadSize = 1;
+      rReq.nodesToRead[0].nodeId = UA_NODEID_NUMERIC(0, 2258);
+      rReq.nodesToRead[0].attributeId = UA_ATTRIBUTEID_VALUE;
+
+      UA_ReadResponse rResp = UA_Client_read(client, &rReq);
+      if(rResp.responseHeader.serviceResult == UA_STATUSCODE_GOOD &&
+         rResp.resultsSize > 0 && rResp.results[0].hasValue &&
+         UA_Variant_isScalar(&rResp.results[0].value) &&
+         rResp.results[0].value.type == &UA_TYPES[UA_TYPES_DATETIME]) {
+             raw_date = *(UA_DateTime*)rResp.results[0].value.data;
+             printf("raw date is: %llu\n", raw_date);
+      }
+      
+      UA_ReadRequest_deleteMembers(&rReq);
+      UA_ReadResponse_deleteMembers(&rResp);
+
+      UA_Client_disconnect(client);
+      UA_Client_delete(client);
+      return 0;
+    } 
+
+You should see raw time in milliseconds since January 1, 1601 UTC midnight::
+
+    :myApp> ./myClient
+    :myApp> raw date is: 130856974061125520
+    
+Firstly we constructed a read request "rReq", it contains 1 node's attribute we want to query for. The attribute is filled with the numeric id "UA_NODEID_NUMERIC(0, 2258)" and the attribute we are reading "UA_ATTRIBUTEID_VALUE". After the read request was sent, we can find the actual read value in the read response.
+
+As the last step for this tutorial, we are going to convert the raw date value into a well formatted string::
+
+    #include <stdio.h>
+    
+    #include "ua_types.h"
+    #include "ua_server.h"
+    #include "logger_stdout.h"
+    #include "networklayer_tcp.h"
+    
+    int main(void) {
+      UA_Client *client = UA_Client_new(UA_ClientConfig_standard, Logger_Stdout_new());
+      UA_StatusCode retval = UA_Client_connect(client, ClientNetworkLayerTCP_connect, "opc.tcp://localhost:16664");
+      if(retval != UA_STATUSCODE_GOOD) {
+        UA_Client_delete(client);
+        return retval;
+      }
+    
+      //variables to store data
+      UA_DateTime raw_date = 0;
+      UA_String* string_date = UA_String_new();
+
+      UA_ReadRequest rReq;
+      UA_ReadRequest_init(&rReq);
+      rReq.nodesToRead = UA_Array_new(&UA_TYPES[UA_TYPES_READVALUEID], 1);
+      rReq.nodesToReadSize = 1;
+      rReq.nodesToRead[0].nodeId = UA_NODEID_NUMERIC(0, 2258);
+      rReq.nodesToRead[0].attributeId = UA_ATTRIBUTEID_VALUE;
+
+      UA_ReadResponse rResp = UA_Client_read(client, &rReq);
+      if(rResp.responseHeader.serviceResult == UA_STATUSCODE_GOOD &&
+         rResp.resultsSize > 0 && rResp.results[0].hasValue &&
+         UA_Variant_isScalar(&rResp.results[0].value) &&
+         rResp.results[0].value.type == &UA_TYPES[UA_TYPES_DATETIME]) {
+             raw_date = *(UA_DateTime*)rResp.results[0].value.data;
+             printf("raw date is: %llu\n", raw_date);
+             UA_DateTime_toString(raw_date, string_date);
+             printf("string date is: %.*s\n", string_date->length, string_date->data);
+      }
+      
+      UA_ReadRequest_deleteMembers(&rReq);
+      UA_ReadResponse_deleteMembers(&rResp);
+      UA_String_delete(string_date);
+
+      UA_Client_disconnect(client);
+      UA_Client_delete(client);
+      return 0;
+    }
+    
+Now you should see raw time and a formatted date::
+
+    :myApp> ./myClient
+    :myApp> raw date is: 130856981449041870
+            string date is: 09/02/2015 20:09:04.904.187.000
+
+Further tasks
+-------------
+* Display the value of the variable node (ns=1,i="the.answer") containing an "Int32" from the example server (which is built in :doc:`tutorial_firstStepsServer`). Note that the identifier of this node is a string type: use "UA_NODEID_STRING_ALLOC". The answer can be found in "examples/exampleClient.c".
+* 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_firstStepsServer`) using "UA_Client_write" function. The example server needs some more modifications, i.e., changing request types. The answer can be found in "examples/exampleClient.c".

doc/tutorials.rst

@@ -1,7 +1,7 @@
 Tutorials
 =========
 
-First steps with open62541-server
+Tutorial 1: First steps with open62541-server
 ------------------------------
 
 :doc:`tutorial_firstStepsServer`
@@ -16,7 +16,7 @@ Contents:
 
 * Compiling built-in server and client examples
 
-First steps with open62541-client
+Tutorial 2: First steps with open62541-client
 ------------------------------
 
 :doc:`tutorial_firstStepsClient`
@@ -27,4 +27,8 @@ Contents:
 
 * Creating a minimal client
 
+* Minimalistic introduction to OPC UA nodes and node IDs
+
 * Reading a variable
+
+* Introduction to stings

examples/client.c

@@ -1,240 +1,44 @@
-#ifdef UA_NO_AMALGAMATION
-# include "ua_types.h"
-# include "ua_client.h"
-# include "ua_nodeids.h"
-# include "networklayer_tcp.h"
-# include "logger_stdout.h"
-# include "ua_types_encoding_binary.h"
-#else
-# include "open62541.h"
-# include <string.h>
-# include <stdlib.h>
-#endif
-
 #include <stdio.h>
 
-void handler_TheAnswerChanged(UA_UInt32 handle, UA_DataValue *value);
-void handler_TheAnswerChanged(UA_UInt32 handle, UA_DataValue *value) {
-    printf("The Answer has changed!\n");
-    return;
-}
-
-int main(int argc, char *argv[]) {
-    UA_Client *client = UA_Client_new(UA_ClientConfig_standard, Logger_Stdout_new());
-    UA_StatusCode retval = UA_Client_connect(client, ClientNetworkLayerTCP_connect,
-                                             "opc.tcp://localhost:16664");
-
-    if(retval != UA_STATUSCODE_GOOD) {
-        UA_Client_delete(client);
-        return retval;
-    }
-    // Browse some objects
-    printf("Browsing nodes in objects folder:\n");
-
-    UA_BrowseRequest bReq;
-    UA_BrowseRequest_init(&bReq);
-    bReq.requestedMaxReferencesPerNode = 0;
-    bReq.nodesToBrowse = UA_BrowseDescription_new();
-    bReq.nodesToBrowseSize = 1;
-    bReq.nodesToBrowse[0].nodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER); //browse objects folder
-    bReq.nodesToBrowse[0].resultMask = UA_BROWSERESULTMASK_ALL; //return everything
-
-    UA_BrowseResponse bResp = UA_Client_browse(client, &bReq);
-    printf("%-9s %-16s %-16s %-16s\n", "NAMESPACE", "NODEID", "BROWSE NAME", "DISPLAY NAME");
-    for (int i = 0; i < bResp.resultsSize; ++i) {
-        for (int j = 0; j < bResp.results[i].referencesSize; ++j) {
-            UA_ReferenceDescription *ref = &(bResp.results[i].references[j]);
-            if(ref->nodeId.nodeId.identifierType == UA_NODEIDTYPE_NUMERIC) {
-                printf("%-9d %-16d %-16.*s %-16.*s\n", ref->browseName.namespaceIndex,
-                       ref->nodeId.nodeId.identifier.numeric, ref->browseName.name.length,
-                       ref->browseName.name.data, ref->displayName.text.length, ref->displayName.text.data);
-            } else if(ref->nodeId.nodeId.identifierType == UA_NODEIDTYPE_STRING) {
-                printf("%-9d %-16.*s %-16.*s %-16.*s\n", ref->browseName.namespaceIndex,
-                       ref->nodeId.nodeId.identifier.string.length, ref->nodeId.nodeId.identifier.string.data,
-                       ref->browseName.name.length, ref->browseName.name.data, ref->displayName.text.length,
-                       ref->displayName.text.data);
-            }
-            //TODO: distinguish further types
-        }
-    }
-    UA_BrowseRequest_deleteMembers(&bReq);
-    UA_BrowseResponse_deleteMembers(&bResp);
-    
-#ifdef ENABLE_SUBSCRIPTIONS
-    // Create a subscription with interval 0 (immediate)...
-    UA_Int32 subId = UA_Client_newSubscription(client, 0);
-    if (subId)
-        printf("Create subscription succeeded, id %u\n", subId);
-    
-    // .. and monitor TheAnswer
-    UA_NodeId monitorThis;
-    monitorThis = UA_NODEID_STRING_ALLOC(1, "the.answer");
-    UA_UInt32 monId = UA_Client_monitorItemChanges(client, subId, monitorThis, UA_ATTRIBUTEID_VALUE, &handler_TheAnswerChanged );
-    if (monId)
-        printf("Monitoring 'the.answer', id %u\n", subId);
-    UA_NodeId_deleteMembers(&monitorThis);
-    
-    // First Publish always generates data (current value) and call out handler.
-    UA_Client_doPublish(client);
-    
-    // This should not generate anything
-    UA_Client_doPublish(client);
-#endif
-    
-    UA_Int32 value = 0;
-    // Read node's value
-    printf("\nReading the value of node (1, \"the.answer\"):\n");
-    UA_ReadRequest rReq;
-    UA_ReadRequest_init(&rReq);
-    rReq.nodesToRead = UA_ReadValueId_new();
-    rReq.nodesToReadSize = 1;
-    rReq.nodesToRead[0].nodeId = UA_NODEID_STRING_ALLOC(1, "the.answer"); /* assume this node exists */
-    rReq.nodesToRead[0].attributeId = UA_ATTRIBUTEID_VALUE;
+#include "ua_types.h"
+#include "ua_server.h"
+#include "logger_stdout.h"
+#include "networklayer_tcp.h"
 
-    UA_ReadResponse rResp = UA_Client_read(client, &rReq);
-    if(rResp.responseHeader.serviceResult == UA_STATUSCODE_GOOD &&
-       rResp.resultsSize > 0 && rResp.results[0].hasValue &&
-       UA_Variant_isScalar(&rResp.results[0].value) &&
-       rResp.results[0].value.type == &UA_TYPES[UA_TYPES_INT32]) {
-        value = *(UA_Int32*)rResp.results[0].value.data;
-        printf("the value is: %i\n", value);
-    }
-
-    UA_ReadRequest_deleteMembers(&rReq);
-    UA_ReadResponse_deleteMembers(&rResp);
-
-    value++;
-    // Write node's value
-    printf("\nWriting a value of node (1, \"the.answer\"):\n");
-    UA_WriteRequest wReq;
-    UA_WriteRequest_init(&wReq);
-    wReq.nodesToWrite = UA_WriteValue_new();
-    wReq.nodesToWriteSize = 1;
-    wReq.nodesToWrite[0].nodeId = UA_NODEID_STRING_ALLOC(1, "the.answer"); /* assume this node exists */
-    wReq.nodesToWrite[0].attributeId = UA_ATTRIBUTEID_VALUE;
-    wReq.nodesToWrite[0].value.hasValue = UA_TRUE;
-    wReq.nodesToWrite[0].value.value.type = &UA_TYPES[UA_TYPES_INT32];
-    wReq.nodesToWrite[0].value.value.storageType = UA_VARIANT_DATA_NODELETE; //do not free the integer on deletion
-    wReq.nodesToWrite[0].value.value.data = &value;
-    
-    UA_WriteResponse wResp = UA_Client_write(client, &wReq);
-    if(wResp.responseHeader.serviceResult == UA_STATUSCODE_GOOD)
-            printf("the new value is: %i\n", value);
-    UA_WriteRequest_deleteMembers(&wReq);
-    UA_WriteResponse_deleteMembers(&wResp);
-
-#ifdef ENABLE_SUBSCRIPTIONS
-    // Take another look at the.answer... this should call the handler.
-    UA_Client_doPublish(client);
-    
-    // Delete our subscription (which also unmonitors all items)
-    if(!UA_Client_removeSubscription(client, subId))
-        printf("Subscription removed\n");
-#endif
-    
-#ifdef ENABLE_METHODCALLS
-    /* Note:  This example requires Namespace 0 Node 11489 (ServerType -> GetMonitoredItems) 
-       FIXME: Provide a namespace 0 independant example on the server side
-     */
-    UA_Variant input;
-    
-    UA_String argString = UA_STRING("Hello Server");
-    UA_Variant_init(&input);
-    UA_Variant_setScalarCopy(&input, &argString, &UA_TYPES[UA_TYPES_STRING]);
-    
-    UA_Int32 outputSize;
-    UA_Variant *output;
-    
-    retval = UA_Client_CallServerMethod(client, UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-                                        UA_NODEID_NUMERIC(1, 62541), 1, &input, &outputSize, &output);
-    if(retval == UA_STATUSCODE_GOOD) {
-        printf("Method call was successfull, and %i returned values available.\n", outputSize);
-        UA_Array_delete(output, &UA_TYPES[UA_TYPES_VARIANT], outputSize);
-    } else {
-        printf("Method call was unsuccessfull, and %x returned values available.\n", retval);
-    }
-    UA_Variant_deleteMembers(&input);
-
-#endif
-
-#ifdef ENABLE_ADDNODES 
-    /* Create a new object type node */
-    // New ReferenceType
-    UA_AddNodesResponse *adResp = UA_Client_createReferenceTypeNode(client,
-        UA_EXPANDEDNODEID_NUMERIC(1, 12133), // Assign this NodeId (will fail if client is called multiple times)
-        UA_QUALIFIEDNAME(0, "NewReference"),
-        UA_LOCALIZEDTEXT("en_US", "TheNewReference"),
-        UA_LOCALIZEDTEXT("en_US", "References something that might or might not exist."),
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-        UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
-        (UA_UInt32) 0, (UA_UInt32) 0, 
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-        UA_LOCALIZEDTEXT("en_US", "IsNewlyReferencedBy"));
-    if (adResp->resultsSize > 0 && adResp->results[0].statusCode == UA_STATUSCODE_GOOD ) {
-        printf("Created 'NewReference' with numeric NodeID %u\n", adResp->results[0].addedNodeId.identifier.numeric );
-    }
-    UA_AddNodesResponse_deleteMembers(adResp);
-    free(adResp);
-    
-    // New ObjectType
-    adResp = UA_Client_createObjectTypeNode(client,    
-        UA_EXPANDEDNODEID_NUMERIC(1, 12134), // Assign this NodeId (will fail if client is called multiple times)
-        UA_QUALIFIEDNAME(0, "NewObjectType"),
-        UA_LOCALIZEDTEXT("en_US", "TheNewObjectType"),
-        UA_LOCALIZEDTEXT("en_US", "Put innovative description here."),
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-        UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
-        (UA_UInt32) 0, (UA_UInt32) 0, 
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER));
-        if (adResp->resultsSize > 0 && adResp->results[0].statusCode == UA_STATUSCODE_GOOD ) {
-        printf("Created 'NewObjectType' with numeric NodeID %u\n", adResp->results[0].addedNodeId.identifier.numeric );
-    }
-    
-    // New Object
-    adResp = UA_Client_createObjectNode(client,    
-        UA_EXPANDEDNODEID_NUMERIC(1, 0), // Assign new/random NodeID  
-        UA_QUALIFIEDNAME(0, "TheNewGreatNodeBrowseName"),
-        UA_LOCALIZEDTEXT("en_US", "TheNewGreatNode"),
-        UA_LOCALIZEDTEXT("de_DE", "Hier koennte Ihre Webung stehen!"),
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-        UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
-        (UA_UInt32) 0, (UA_UInt32) 0, 
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER));
-    if (adResp->resultsSize > 0 && adResp->results[0].statusCode == UA_STATUSCODE_GOOD ) {
-        printf("Created 'NewObject' with numeric NodeID %u\n", adResp->results[0].addedNodeId.identifier.numeric );
-    }
-    
-    UA_AddNodesResponse_deleteMembers(adResp);
-    free(adResp);
-    
-    // New Integer Variable
-    UA_Variant *theValue = UA_Variant_new();
-    UA_Int32 *theValueDate = UA_Int32_new();
-    *theValueDate = 1234;
-    theValue->type = &UA_TYPES[UA_TYPES_INT32];
-    theValue->data = theValueDate;
-    
-    adResp = UA_Client_createVariableNode(client,
-        UA_EXPANDEDNODEID_NUMERIC(1, 0), // Assign new/random NodeID  
-        UA_QUALIFIEDNAME(0, "VariableNode"),
-        UA_LOCALIZEDTEXT("en_US", "TheNewVariableNode"),
-        UA_LOCALIZEDTEXT("en_US", "This integer is just amazing - it has digits and everything."),
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-        UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
-        (UA_UInt32) 0, (UA_UInt32) 0, 
-        UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
-        UA_NODEID_NUMERIC(0, UA_NS0ID_INT32),
-        theValue);
-    if (adResp->resultsSize > 0 && adResp->results[0].statusCode == UA_STATUSCODE_GOOD ) {
-        printf("Created 'NewVariable' with numeric NodeID %u\n", adResp->results[0].addedNodeId.identifier.numeric );
-    }
-    UA_AddNodesResponse_deleteMembers(adResp);
-    free(adResp);
-    free(theValue);
-    /* Done creating a new node*/
-#endif
-    UA_Client_disconnect(client);
+int main(void) {
+  UA_Client *client = UA_Client_new(UA_ClientConfig_standard, Logger_Stdout_new());
+  UA_StatusCode retval = UA_Client_connect(client, ClientNetworkLayerTCP_connect, "opc.tcp://localhost:16664");
+  if(retval != UA_STATUSCODE_GOOD) {
     UA_Client_delete(client);
-    return UA_STATUSCODE_GOOD;
+    return retval;
+  }
+
+  UA_DateTime raw_date = 0;
+  UA_String* string_date = UA_String_new();
+  // Read node's value
+  UA_ReadRequest rReq;
+  UA_ReadRequest_init(&rReq);
+  rReq.nodesToRead = UA_Array_new(&UA_TYPES[UA_TYPES_READVALUEID], 1);
+  rReq.nodesToReadSize = 1;
+  rReq.nodesToRead[0].nodeId = UA_NODEID_NUMERIC(0, 2258);
+  rReq.nodesToRead[0].attributeId = UA_ATTRIBUTEID_VALUE;
+
+  UA_ReadResponse rResp = UA_Client_read(client, &rReq);
+  if(rResp.responseHeader.serviceResult == UA_STATUSCODE_GOOD &&
+     rResp.resultsSize > 0 && rResp.results[0].hasValue &&
+     UA_Variant_isScalar(&rResp.results[0].value) &&
+     rResp.results[0].value.type == &UA_TYPES[UA_TYPES_DATETIME]) {
+      raw_date = *(UA_DateTime*)rResp.results[0].value.data;
+      printf("raw date is: %llu\n", raw_date);
+      UA_DateTime_toString(raw_date, string_date);
+      printf("string date is: %.*s\n", string_date->length, string_date->data);
+  }
+
+  UA_ReadRequest_deleteMembers(&rReq);
+  UA_ReadResponse_deleteMembers(&rResp);
+  UA_String_delete(string_date);
+
+  UA_Client_disconnect(client);
+  UA_Client_delete(client);
+  return 0;
 }
-