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

 #include <signal.h>
 #include "open62541.h"
    UA_Boolean running = true;
    static void stopHandler(int sig)
      {
    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "received ctrl-c");
    running = false;
    }
 int main(void) {
    signal(SIGINT, stopHandler);
    signal(SIGTERM, stopHandler);
    UA_ServerConfig *config = UA_ServerConfig_new_default();
    UA_Server *server = UA_Server_new(config);
    UA_StatusCode retval = UA_Server_run(server, &running);
    UA_Server_delete(server);
    UA_ServerConfig_delete(config);
    return (int)retval;
    }

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。

 #include <signal.h>
 #include <stdio.h>
 #include "open62541.h"
 static void
 addVariable(UA_Server *server) {
    /* Define the attribute of the myInteger variable node */
    UA_VariableAttributes attr = UA_VariableAttributes_default;
    UA_Int32 myInteger = ;
    UA_Variant_setScalar(&attr.value, &myInteger, &UA_TYPES[UA_TYPES_INT32]);
    attr.description = UA_LOCALIZEDTEXT("en-US","the answer");
    attr.displayName = UA_LOCALIZEDTEXT("en-US","the answer");
    attr.dataType = UA_TYPES[UA_TYPES_INT32].typeId;
    attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
    /* Add the variable node to the information model */
    UA_NodeId myIntegerNodeId = UA_NODEID_STRING(, "the.answer");
    UA_QualifiedName myIntegerName = UA_QUALIFIEDNAME(, "the answer");
    UA_NodeId parentNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_OBJECTSFOLDER);
    UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_ORGANIZES);
    UA_Server_addVariableNode(server, myIntegerNodeId, parentNodeId,
    parentReferenceNodeId, myIntegerName,
    UA_NODEID_NUMERIC(, UA_NS0ID_BASEDATAVARIABLETYPE),attr, NULL, NULL);
    }

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 。

 static void
 writeVariable(UA_Server *server) {
     UA_NodeId myIntegerNodeId =
     UA_NODEID_STRING(,"the.answer");

     /* Write a different integer value */
     UA_Int32 myInteger = ;
     UA_Variant myVar;
     UA_Variant_init(&myVar);
     UA_Variant_setScalar(&myVar, &myInteger,
     &UA_TYPES[UA_TYPES_INT32]);
     UA_Server_writeValue(server, myIntegerNodeId, myVar);

     /* Set the status code of the value to an error code. The
     function
     * UA_Server_write provides access to the raw service. The
     above
     * UA_Server_writeValue is syntactic sugar for writing a specific
     node
     * attribute with the write service. */
     UA_WriteValue wv;
     UA_WriteValue_init(&wv);
     wv.nodeId = myIntegerNodeId;
     wv.attributeId = UA_ATTRIBUTEID_VALUE;
     wv.value.status = UA_STATUSCODE_BADNOTCONNECTED;
     wv.value.hasStatus = true;
     UA_Server_write(server, &wv);

     /* Reset the variable to a good statuscode with a value */
     wv.value.hasStatus = false;
     wv.value.value = myVar;
     wv.value.hasValue = true;
     UA_Server_write(server, &wv);
     }

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。

 static void
 writeWrongVariable(UA_Server *server) {
    UA_NodeId myIntegerNodeId = UA_NODEID_STRING(, "the.answer");

    /* Write a string */
    UA_String myString = UA_STRING("test");
    UA_Variant myVar;
    UA_Variant_init(&myVar);
    UA_Variant_setScalar(&myVar, &myString,
    &UA_TYPES[UA_TYPES_STRING]);
    UA_StatusCode retval = UA_Server_writeValue(server,
    myIntegerNodeId, myVar);
    printf("Writing a string returned statuscode %s\n",
    UA_StatusCode_name(retval));
    }

它遵循主服务器代码，使用上述定义。

 UA_Boolean running = true;
 static void stopHandler(int sign) {
 UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "received ctrl-c");
 running = false;
 }

 int main(void) {
    signal(SIGINT, stopHandler);
    signal(SIGTERM, stopHandler);

    UA_ServerConfig *config = UA_ServerConfig_new_default();
    UA_Server *server = UA_Server_new(config);

    addVariable(server);
    writeVariable(server);
    writeWrongVariable(server);

    UA_StatusCode retval = UA_Server_run(server, &running);
    UA_Server_delete(server);
    UA_ServerConfig_delete(config);
    return (int)retval;
    }

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。

 #include <signal.h>
 #include "open62541.h"
 #pragma comment(lib, "WS2_32")
 static void
 updateCurrentTime(UA_Server *server) {
     UA_DateTime now = UA_DateTime_now();
     UA_Variant value;
     UA_Variant_setScalar(&value, &now, &UA_TYPES[UA_TYPES_DATETIME]);
     UA_NodeId currentNodeId = UA_NODEID_STRING(, "current-time");
     UA_Server_writeValue(server, currentNodeId, value);
 }
 static void
 addCurrentTimeVariable(UA_Server *server) {
     UA_DateTime now = ;
     UA_VariableAttributes attr = UA_VariableAttributes_default;
     attr.displayName = UA_LOCALIZEDTEXT("en-US", "Current time");
     attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
     UA_Variant_setScalar(&attr.value, &now, &UA_TYPES[UA_TYPES_DATETIME]);
     UA_NodeId currentNodeId = UA_NODEID_STRING(, "current-time");
     UA_QualifiedName currentName = UA_QUALIFIEDNAME(, "current-time");
     UA_NodeId parentNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_OBJECTSFOLDER);
     UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_ORGANIZES);
     UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_BASEDATAVARIABLETYPE);
     UA_Server_addVariableNode(server, currentNodeId, parentNodeId,
         parentReferenceNodeId, currentName,
         variableTypeNodeId, attr, NULL, NULL);
     updateCurrentTime(server);
 }

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。

 static void
 beforeReadTime(UA_Server *server,
     const UA_NodeId *sessionId, void *sessionContext,
     const UA_NodeId *nodeid, void *nodeContext,
     const UA_NumericRange *range, const UA_DataValue *data) {
     UA_DateTime now = UA_DateTime_now();
     UA_Variant value;
     UA_Variant_setScalar(&value, &now, &UA_TYPES[UA_TYPES_DATETIME]);
     UA_NodeId currentNodeId = UA_NODEID_STRING(, "current-time");
     UA_Server_writeValue(server, currentNodeId, value);
 }
 static void
 afterWriteTime(UA_Server *server,
     const UA_NodeId *sessionId, void *sessionContext,
     const UA_NodeId *nodeId, void *nodeContext,
     const UA_NumericRange *range, const UA_DataValue *data) {
     UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
         "The variable was updated");
 }
 static void
 addValueCallbackToCurrentTimeVariable(UA_Server *server) {
     UA_NodeId currentNodeId = UA_NODEID_STRING(, "current-time");
     UA_ValueCallback callback;
     callback.onRead = beforeReadTime;
     callback.onWrite = afterWriteTime;
     UA_Server_setVariableNode_valueCallback(server, currentNodeId, callback);
 }

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。

 static UA_StatusCode
 readCurrentTime(UA_Server *server,
     const UA_NodeId *sessionId, void *sessionContext,
     const UA_NodeId *nodeId, void *nodeContext,
     UA_Boolean sourceTimeStamp, const UA_NumericRange *range,
     UA_DataValue *dataValue) {
     UA_DateTime now = UA_DateTime_now();
     UA_Variant_setScalarCopy(&dataValue->value, &now,
         &UA_TYPES[UA_TYPES_DATETIME]);
     dataValue->hasValue = true;
     return UA_STATUSCODE_GOOD;
 }

 static UA_StatusCode
 writeCurrentTime(UA_Server *server,
     const UA_NodeId *sessionId, void *sessionContext,
     const UA_NodeId *nodeId, void *nodeContext,
     const UA_NumericRange *range, const UA_DataValue *data) {
     UA_LOG_INFO(UA_Log_out, UA_LOGCATEGORY_USERLAND,
         "Changing the system time is not implemented");
     return UA_STATUSCODE_GOOD;
 }

 static void
 addCurrentTimeDataSourceVariable(UA_Server *server) {
     UA_VariableAttributes attr = UA_VariableAttributes_default;
     attr.displayName = UA_LOCALIZEDTEXT("en-US", "Current time - data source");
     attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;
     UA_NodeId currentNodeId = UA_NODEID_STRING(, "current-time-datasource");
     UA_QualifiedName currentName = UA_QUALIFIEDNAME(, "current-time-datasource");
     UA_NodeId parentNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_OBJECTSFOLDER);
     UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_ORGANIZES);
     UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(, UA_NS0ID_BASEDATAVARIABLETYPE);
     UA_DataSource timeDataSource;
     timeDataSource.read = readCurrentTime;
     timeDataSource.write = writeCurrentTime;
     UA_Server_addDataSourceVariableNode(server, currentNodeId, parentNodeId,
         parentReferenceNodeId, currentName,
         variableTypeNodeId, attr,
         timeDataSource, NULL, NULL);
 }

以下代码遵循主服务器代码，使用上述定义。

 UA_Boolean running = true;
 static void stopHandler(int sign) {
     UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "received ctrl-c");
     running = false;
 }
 int main(void) {
     signal(SIGINT, stopHandler);
     signal(SIGTERM, stopHandler);
     UA_ServerConfig *config = UA_ServerConfig_new_default();
     UA_Server *server = UA_Server_new(config);
     addCurrentTimeVariable(server);
     addValueCallbackToCurrentTimeVariable(server);
     addCurrentTimeDataSourceVariable(server);
     UA_StatusCode retval = UA_Server_run(server, &running);
     UA_Server_delete(server);
     UA_ServerConfig_delete(config);
     return (int)retval;
 }