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81 lines
3.1 KiB
C
81 lines
3.1 KiB
C
/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
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* See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */
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/**
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* Building a Simple Client
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* ------------------------
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* You should already have a basic server from the previous tutorials. open62541
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* provides both a server- and clientside API, so creating a client is as easy as
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* creating a server. Copy the following into a file `myClient.c`: */
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#include <open62541/client_config_default.h>
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#include <open62541/client_highlevel.h>
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#include <open62541/plugin/log_stdout.h>
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int main(void) {
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UA_Client *client = UA_Client_new();
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UA_ClientConfig_setDefault(UA_Client_getConfig(client));
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UA_StatusCode retval = UA_Client_connect(client, "opc.tcp://localhost:4840");
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if(retval != UA_STATUSCODE_GOOD) {
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UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
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"The connection failed with status code %s",
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UA_StatusCode_name(retval));
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UA_Client_delete(client);
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return 0;
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}
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/* Read the value attribute of the node. UA_Client_readValueAttribute is a
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* wrapper for the raw read service available as UA_Client_Service_read. */
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UA_Variant value; /* Variants can hold scalar values and arrays of any type */
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UA_Variant_init(&value);
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/* NodeId of the variable holding the current time */
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const UA_NodeId nodeId = UA_NS0ID(SERVER_SERVERSTATUS_CURRENTTIME);
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retval = UA_Client_readValueAttribute(client, nodeId, &value);
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if(retval == UA_STATUSCODE_GOOD &&
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UA_Variant_hasScalarType(&value, &UA_TYPES[UA_TYPES_DATETIME])) {
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UA_DateTime raw_date = *(UA_DateTime *) value.data;
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UA_DateTimeStruct dts = UA_DateTime_toStruct(raw_date);
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UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
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"date is: %u-%u-%u %u:%u:%u.%03u",
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dts.day, dts.month, dts.year, dts.hour,
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dts.min, dts.sec, dts.milliSec);
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} else {
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UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
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"Reading the value failed with status code %s",
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UA_StatusCode_name(retval));
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}
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/* Clean up */
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UA_Variant_clear(&value);
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UA_Client_delete(client); /* Disconnects the client internally */
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return 0;
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}
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/**
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* Compilation is similar to the server example.
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*
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* .. code-block:: bash
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*
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* $ gcc -std=c99 myClient.c -lopen62541 -o myClient
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*
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* In a MinGW environment, the Winsock library must be added.
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*
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* .. code-block:: bash
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*
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* $ gcc -std=c99 myClient.c -lopen62541 -lws2_32 -o myClient.exe
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*
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* Further tasks
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* ^^^^^^^^^^^^^
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*
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* - Try to connect to some other OPC UA server by changing
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* ``opc.tcp://localhost:4840`` to an appropriate address (remember that the
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* queried node is contained in any OPC UA server).
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*
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* - Try to set the value of the variable node (ns=1,i="the.answer") containing
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* an ``Int32`` from the example server (which is built in
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* :doc:`tutorial_server_firststeps`) using "UA_Client_write" function. The
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* example server needs some more modifications, i.e., changing request types.
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* The answer can be found in ``examples/client.c``. */
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