基於open62541的opc ua 伺服器開發實現（1）

伺服器 · 發表 2019-04-20 20:15:00

摘要：關於opcua的介紹這裡就不多說了，相信大家大都有了一些瞭解，open62541 是一個開源C（C99）的opc-ua實現，開原始碼可在官網或github上下載。話不多說，首先搭建一個opcua伺服器例項 1 #include <...

關於opcua的介紹這裡就不多說了，相信大家大都有了一些瞭解，open62541 是一個開源C（C99）的opc-ua實現，開原始碼可在官網或github上下載。

話不多說，首先搭建一個opcua伺服器例項

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

以下程式碼演示如何使用資料型別以及如何向伺服器新增變數節點。首先，我們向伺服器新增一個新變數。檢視UA變數屬性結構的定義，以檢視為變數節點定義的所有屬性的列表。請注意，預設設定將變數值的訪問級別設定為只讀。有關使變數可寫的資訊，請參見下文。

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

現在我們用寫服務更改節點值。也可以通過網路由OPC UA的客戶端訪問來修改值。

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

注意我們最初如何將變數節點的data type屬性設定為int32資料型別的nodeid。這禁止寫入非Int32的值。下面的程式碼顯示瞭如何對每次寫入執行一致性檢查。

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

它遵循主伺服器程式碼，使用上述定義。

 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) {
 8signal(SIGINT, stopHandler);
 9signal(SIGTERM, stopHandler);
10
11UA_ServerConfig *config = UA_ServerConfig_new_default();
12UA_Server *server = UA_Server_new(config);
13 
14addVariable(server);
15writeVariable(server);
16writeWrongVariable(server);
17 
18UA_StatusCode retval = UA_Server_run(server, &running);
19UA_Server_delete(server);
20UA_ServerConfig_delete(config);
21return (int)retval;
22}

在基於OPC UA的體系結構中，伺服器通常位於資訊源附近。在工業環境中，這意味著伺服器接近物理過程，客戶機在執行時使用資料。在前面的教程中，我們看到了如何向OPC UA資訊模型新增變數。本例項演示如何將變數連線到執行時資訊，例如從物理過程的測量中連線。為簡單起見，我們以系統時鐘為基礎的“過程”。以下程式碼段分別與執行時更新變數值的不同方式有關。總之，程式碼片段定義了一個可編譯的原始檔。

作為起點，假設已在伺服器中為datetime型別的值建立了一個識別符號為“ns=1，s=current time”的變數。假設當一個新的值從底層程序到達時，我們的應用程式被觸發，我們可以直接寫入變數。

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

2.值回撥

當一個值不斷變化時，例如系統時間，在一個緊密的迴圈中更新該值將佔用大量的資源。值回撥允許將變數值與外部表示同步。它們將回調附加到每次讀操作之前和每次寫操作之後執行的變數。

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

3.變數資料來源

對於值回撥，該值仍儲存在變數節點中。所謂的資料來源更進一步。伺服器將每個讀寫請求重定向到回撥函式。在讀取時，回撥提供當前值的副本。在內部，資料來源需要實現自己的記憶體管理。

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

以下程式碼遵循主伺服器程式碼，使用上述定義。


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

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基於open62541的opc ua 伺服器開發實現（1）

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