| /* This work is licensed under a Creative Commons CCZero 1.0 Universal License. |
| * See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */ |
| |
| /** |
| * Connecting a Variable with a Physical Process |
| * --------------------------------------------- |
| * |
| * In OPC UA-based architectures, servers are typically situated near the source |
| * of information. In an industrial context, this translates into servers being |
| * near the physical process and clients consuming the data at runtime. In the |
| * previous tutorial, we saw how to add variables to an OPC UA information |
| * model. This tutorial shows how to connect a variable to runtime information, |
| * for example from measurements of a physical process. For simplicity, we take |
| * the system clock as the underlying "process". |
| * |
| * The following code snippets are each concerned with a different way of |
| * updating variable values at runtime. Taken together, the code snippets define |
| * a compilable source file. |
| * |
| * Updating variables manually |
| * ^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| * As a starting point, assume that a variable for a value of type |
| * :ref:`datetime` has been created in the server with the identifier |
| * "ns=1,s=current-time". Assuming that our applications gets triggered when a |
| * new value arrives from the underlying process, we can just write into the |
| * variable. */ |
| |
| #include <open62541/plugin/log_stdout.h> |
| #include <open62541/server.h> |
| #include <open62541/server_config_default.h> |
| |
| #include <signal.h> |
| #include <stdlib.h> |
| |
| 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(1, "current-time-value-callback"); |
| UA_Server_writeValue(server, currentNodeId, value); |
| } |
| |
| static void |
| addCurrentTimeVariable(UA_Server *server) { |
| UA_DateTime now = 0; |
| UA_VariableAttributes attr = UA_VariableAttributes_default; |
| attr.displayName = UA_LOCALIZEDTEXT("en-US", "Current time - value callback"); |
| 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(1, "current-time-value-callback"); |
| UA_QualifiedName currentName = UA_QUALIFIEDNAME(1, "current-time-value-callback"); |
| UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER); |
| UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES); |
| UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE); |
| UA_Server_addVariableNode(server, currentNodeId, parentNodeId, |
| parentReferenceNodeId, currentName, |
| variableTypeNodeId, attr, NULL, NULL); |
| |
| updateCurrentTime(server); |
| } |
| |
| /** |
| * Variable Value Callback |
| * ^^^^^^^^^^^^^^^^^^^^^^^ |
| * |
| * When a value changes continuously, such as the system time, updating the |
| * value in a tight loop would take up a lot of resources. Value callbacks allow |
| * to synchronize a variable value with an external representation. They attach |
| * callbacks to the variable that are executed before every read and after every |
| * write operation. */ |
| |
| 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) { |
| updateCurrentTime(server); |
| } |
| |
| 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(1, "current-time-value-callback"); |
| UA_ValueCallback callback ; |
| callback.onRead = beforeReadTime; |
| callback.onWrite = afterWriteTime; |
| UA_Server_setVariableNode_valueCallback(server, currentNodeId, callback); |
| } |
| |
| /** |
| * Variable Data Sources |
| * ^^^^^^^^^^^^^^^^^^^^^ |
| * |
| * With value callbacks, the value is still stored in the variable node. |
| * So-called data sources go one step further. The server redirects every read |
| * and write request to a callback function. Upon reading, the callback provides |
| * copy of the current value. Internally, the data source needs to implement its |
| * own memory management. */ |
| |
| 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_Stdout, UA_LOGCATEGORY_USERLAND, |
| "Changing the system time is not implemented"); |
| return UA_STATUSCODE_BADINTERNALERROR; |
| } |
| |
| 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(1, "current-time-datasource"); |
| UA_QualifiedName currentName = UA_QUALIFIEDNAME(1, "current-time-datasource"); |
| UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER); |
| UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES); |
| UA_NodeId variableTypeNodeId = UA_NODEID_NUMERIC(0, 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); |
| } |
| |
| /** It follows the main server code, making use of the above definitions. */ |
| |
| static volatile 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_Server *server = UA_Server_new(); |
| UA_ServerConfig_setDefault(UA_Server_getConfig(server)); |
| |
| addCurrentTimeVariable(server); |
| addValueCallbackToCurrentTimeVariable(server); |
| addCurrentTimeDataSourceVariable(server); |
| |
| UA_StatusCode retval = UA_Server_run(server, &running); |
| |
| UA_Server_delete(server); |
| return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE; |
| } |