基于open62541的opc ua 服务器开发实现（1）

关于opcua的介绍这里就不多说了，相信大家大都有了一些了解，open62541是一个开源C（C99）的opc-ua实现，开源代码可在官网或github上下载。

话不多说，首先搭建一个opcua服务器实例

 1 #include 
 2 #include "open62541.h"
 3    UA_Boolean running = true;
 4    static void stopHandler(int sig)
      {
 5    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "received ctrl-c");
 6    running = false;
 7    }
 8 int main(void) {
 9    signal(SIGINT, stopHandler);
10    signal(SIGTERM, stopHandler);
11    UA_ServerConfig *config = UA_ServerConfig_new_default();
12    UA_Server *server = UA_Server_new(config);
13    UA_StatusCode retval = UA_Server_run(server, &running);
14    UA_Server_delete(server);
15    UA_ServerConfig_delete(config);
16    return (int)retval;
17    }

以下代码演示如何使用数据类型以及如何向服务器添加变量节点。首先，我们向服务器添加一个新变量。查看UA变量属性结构的定义，以查看为变量节点定义的所有属性的列表。请注意，默认设置将变量值的访问级别设置为只读。有关使变量可写的信息，请参见下文。

 1 #include 
 2 #include 
 3 #include "open62541.h"
 4 static void
 5 addVariable(UA_Server *server) {
 6    /* Define the attribute of the myInteger variable node */
 7    UA_VariableAttributes attr = UA_VariableAttributes_default;
 8    UA_Int32 myInteger = 42;
 9    UA_Variant_setScalar(&attr.value, &myInteger, &UA_TYPES[UA_TYPES_INT32]);
10    attr.description = UA_LOCALIZEDTEXT("en-US","the answer");
11    attr.displayName = UA_LOCALIZEDTEXT("en-US","the answer");
12    attr.dataType = UA_TYPES[UA_TYPES_INT32].typeId;
13    attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
14    /* Add the variable node to the information model */
15    UA_NodeId myIntegerNodeId = UA_NODEID_STRING(1, "the.answer");
16    UA_QualifiedName myIntegerName = UA_QUALIFIEDNAME(1, "the answer");
17    UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
18    UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
19    UA_Server_addVariableNode(server, myIntegerNodeId, parentNodeId,
20    parentReferenceNodeId, myIntegerName,
21    UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE),attr, NULL, NULL);
22    }

现在我们用 写服务 更改节点值。也可以通过网络由OPC UA的客户端访问来修改值 。

 

 1 static void
 2 writeVariable(UA_Server *server) {
 3     UA_NodeId myIntegerNodeId = 
 4     UA_NODEID_STRING(1,"the.answer");
 5 
 6     /* Write a different integer value */
 7     UA_Int32 myInteger = 43;
 8     UA_Variant myVar;
 9     UA_Variant_init(&myVar);
10     UA_Variant_setScalar(&myVar, &myInteger, 
11     &UA_TYPES[UA_TYPES_INT32]);
12     UA_Server_writeValue(server, myIntegerNodeId, myVar);
13 
14     /* Set the status code of the value to an error code. The 
15     function
16     * UA_Server_write provides access to the raw service. The 
17     above
18     * UA_Server_writeValue is syntactic sugar for writing a specific 
19     node
20     * attribute with the write service. */
21     UA_WriteValue wv;
22     UA_WriteValue_init(&wv);
23     wv.nodeId = myIntegerNodeId;
24     wv.attributeId = UA_ATTRIBUTEID_VALUE;
25     wv.value.status = UA_STATUSCODE_BADNOTCONNECTED;
26     wv.value.hasStatus = true;
27     UA_Server_write(server, &wv);
28 
29     /* Reset the variable to a good statuscode with a value */
30     wv.value.hasStatus = false;
31     wv.value.value = myVar;
32     wv.value.hasValue = true;
33     UA_Server_write(server, &wv);
34     }

 

注意我们最初如何将变量节点的data type属性设置为int32数据类型的nodeid。这禁止写入非Int32的值。下面的代码显示了如何对每次写入执行一致性检查。

 1 static void
 2 writeWrongVariable(UA_Server *server) {
 3    UA_NodeId myIntegerNodeId = UA_NODEID_STRING(1, "the.answer");
 4 
 5    /* Write a string */
 6    UA_String myString = UA_STRING("test");
 7    UA_Variant myVar;
 8    UA_Variant_init(&myVar);
 9    UA_Variant_setScalar(&myVar, &myString, 
10    &UA_TYPES[UA_TYPES_STRING]);
11    UA_StatusCode retval = UA_Server_writeValue(server, 
12    myIntegerNodeId, myVar);
13    printf("Writing a string returned statuscode %s\n", 
14    UA_StatusCode_name(retval));
15    }

它遵循主服务器代码，使用上述定义。

 1 UA_Boolean running = true;
 2 static void stopHandler(int sign) {
 3 UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "received ctrl-c");
 4 running = false;
 5 }
 6 
 7 int main(void) {
 8    signal(SIGINT, stopHandler);
 9    signal(SIGTERM, stopHandler);
10  
11    UA_ServerConfig *config = UA_ServerConfig_new_default();
12    UA_Server *server = UA_Server_new(config);
13 
14    addVariable(server);
15    writeVariable(server);
16    writeWrongVariable(server);
17 
18    UA_StatusCode retval = UA_Server_run(server, &running);
19    UA_Server_delete(server);
20    UA_ServerConfig_delete(config);
21    return (int)retval;
22    }

在基于OPC UA的体系结构中，服务器通常位于信息源附近。在工业环境中，这意味着服务器接近物理过程，客户机在运行时使用数据。在前面的教程中，我们看到了如何向OPC UA信息模型添加变量。本实例演示如何将变量连接到运行时信息，例如从物理过程的测量中连接。为简单起见，我们以系统时钟为基础的“过程”。以下代码段分别与运行时更新变量值的不同方式有关。总之，代码片段定义了一个可编译的源文件。

作为起点，假设已在服务器中为datetime类型的值创建了一个标识符为“ns=1，s=current time”的变量。假设当一个新的值从底层进程到达时，我们的应用程序被触发，我们可以直接写入变量。

 1 #include 
 2 #include "open62541.h"
 3 #pragma comment(lib, "WS2_32")
 4 static void
 5 updateCurrentTime(UA_Server *server) {
 6     UA_DateTime now = UA_DateTime_now();
 7     UA_Variant value;
 8     UA_Variant_setScalar(&value, &now, &UA_TYPES[UA_TYPES_DATETIME]);
 9     UA_NodeId currentNodeId = UA_NODEID_STRING(1, "current-time");
10     UA_Server_writeValue(server, currentNodeId, value);
11 }
12 static void
13 addCurrentTimeVariable(UA_Server *server) {
14     UA_DateTime now = 0;
15     UA_VariableAttributes attr = UA_VariableAttributes_default;
16     attr.displayName = UA_LOCALIZEDTEXT("en-US", "Current time");
17     attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
18     UA_Variant_setScalar(&attr.value, &now, &UA_TYPES[UA_TYPES_DATETIME]);
19     UA_NodeId currentNodeId = UA_NODEID_STRING(1, "current-time");
20     UA_QualifiedName currentName = UA_QUALIFIEDNAME(1, "current-time");
21     UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
22     UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
23     UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE);
24     UA_Server_addVariableNode(server, currentNodeId, parentNodeId,
25         parentReferenceNodeId, currentName,
26         variableTypeNodeId, attr, NULL, NULL);
27     updateCurrentTime(server);
28 }

2.值回调

当一个值不断变化时，例如系统时间，在一个紧密的循环中更新该值将占用大量的资源。值回调允许将变量值与外部表示同步。它们将回调附加到每次读操作之前和每次写操作之后执行的变量。

 1 static void
 2 beforeReadTime(UA_Server *server,
 3     const UA_NodeId *sessionId, void *sessionContext,
 4     const UA_NodeId *nodeid, void *nodeContext,
 5     const UA_NumericRange *range, const UA_DataValue *data) {
 6     UA_DateTime now = UA_DateTime_now();
 7     UA_Variant value;
 8     UA_Variant_setScalar(&value, &now, &UA_TYPES[UA_TYPES_DATETIME]);
 9     UA_NodeId currentNodeId = UA_NODEID_STRING(1, "current-time");
10     UA_Server_writeValue(server, currentNodeId, value);
11 }
12 static void
13 afterWriteTime(UA_Server *server,
14     const UA_NodeId *sessionId, void *sessionContext,
15     const UA_NodeId *nodeId, void *nodeContext,
16     const UA_NumericRange *range, const UA_DataValue *data) {
17     UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
18         "The variable was updated");
19 }
20 static void
21 addValueCallbackToCurrentTimeVariable(UA_Server *server) {
22     UA_NodeId currentNodeId = UA_NODEID_STRING(1, "current-time");
23     UA_ValueCallback callback;
24     callback.onRead = beforeReadTime;
25     callback.onWrite = afterWriteTime;
26     UA_Server_setVariableNode_valueCallback(server, currentNodeId, callback);
27 }

3.变量数据源

    对于值回调，该值仍存储在变量节点中。所谓的数据源更进一步。服务器将每个读写请求重定向到回调函数。在读取时，回调提供当前值的副本。在内部，数据源需要实现自己的内存管理。

 1 static UA_StatusCode
 2 readCurrentTime(UA_Server *server,
 3     const UA_NodeId *sessionId, void *sessionContext,
 4     const UA_NodeId *nodeId, void *nodeContext,
 5     UA_Boolean sourceTimeStamp, const UA_NumericRange *range,
 6     UA_DataValue *dataValue) {
 7     UA_DateTime now = UA_DateTime_now();
 8     UA_Variant_setScalarCopy(&dataValue->value, &now,
 9         &UA_TYPES[UA_TYPES_DATETIME]);
10     dataValue->hasValue = true;
11     return UA_STATUSCODE_GOOD;
12 }
13 
14 static UA_StatusCode
15 writeCurrentTime(UA_Server *server,
16     const UA_NodeId *sessionId, void *sessionContext,
17     const UA_NodeId *nodeId, void *nodeContext,
18     const UA_NumericRange *range, const UA_DataValue *data) {
19     UA_LOG_INFO(UA_Log_out, UA_LOGCATEGORY_USERLAND,
20         "Changing the system time is not implemented");
21     return UA_STATUSCODE_GOOD;
22 }
23 
24 static void
25 addCurrentTimeDataSourceVariable(UA_Server *server) {
26     UA_VariableAttributes attr = UA_VariableAttributes_default;
27     attr.displayName = UA_LOCALIZEDTEXT("en-US", "Current time - data source");
28     attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
29     UA_NodeId currentNodeId = UA_NODEID_STRING(1, "current-time-datasource");
30     UA_QualifiedName currentName = UA_QUALIFIEDNAME(1, "current-time-datasource");
31     UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
32     UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
33     UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE);
34     UA_DataSource timeDataSource;
35     timeDataSource.read = readCurrentTime;
36     timeDataSource.write = writeCurrentTime;
37     UA_Server_addDataSourceVariableNode(server, currentNodeId, parentNodeId,
38         parentReferenceNodeId, currentName,
39         variableTypeNodeId, attr,
40         timeDataSource, NULL, NULL);
41 }

以下代码遵循主服务器代码，使用上述定义。

 1 UA_Boolean running = true;
 2 static void stopHandler(int sign) {
 3     UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "received ctrl-c");
 4     running = false;
 5 }
 6 int main(void) {
 7     signal(SIGINT, stopHandler);
 8     signal(SIGTERM, stopHandler);
 9     UA_ServerConfig *config = UA_ServerConfig_new_default();
10     UA_Server *server = UA_Server_new(config);
11     addCurrentTimeVariable(server);
12     addValueCallbackToCurrentTimeVariable(server);
13     addCurrentTimeDataSourceVariable(server);
14     UA_StatusCode retval = UA_Server_run(server, &running);
15     UA_Server_delete(server);
16     UA_ServerConfig_delete(config);
17     return (int)retval;
18 }

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转载于:https://www.cnblogs.com/yuexiachacha/p/10742492.html