Skip to content

Latest commit

 

History

History
736 lines (485 loc) · 21.5 KB

README.md

File metadata and controls

736 lines (485 loc) · 21.5 KB
Raw

A OPC-UA client-server application

Open Platform Communications - Unified Architecture

This lab will guide you through the implementation of a OPC UA application to illustrate client-server communications. Both ends will run locally:

  • Server: contains information about certain robots at factories that perform a certain task
  • Client: queries the server for robots to see if there is a robot available for certain task

In OPC UA, servers may provide information as object nodes and variable nodes. Object nodes can contain other object and variables nodes known as children. Variable nodes can contain other variable nodes.

We are going to implement a server and then a client gathering the built-in information for robots in a factory. This will just scratch the surface of OPC-UA communications.

Server and client implementation are split in a set of small steps to illustrate every concept independently. The complete files are also provided for reference as client.c and server.c. The example is an extension of the tutorials and source from open62541 Tutorials and distributed under the same terms: Public Domain (Creative Commons CC0).

A working Makefile is also provided.

Server

Interruptable process

Let's start with a minimal OPC-UA process that we can interrupt with Ctrl-C. The code would be:

#include <signal.h>
/* Include the OPC-UA open62541 header file */
#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);

    // Our OPC UA server code will replace the loop below
    while (running) {
    }

    return 0;

}

When you deploy this code, you can see, when our process receives SIGINT or SIGTERM, the handler is run, a message is printed by UA_LOG_INFO, and the process exits.

Minimal skeleton

Let's implement the actual server.

Now we will replace the loop:

// Our OPC UA server code will replace the loop below
while (running) {
}

by the actual server code.

The first step is setting up the configuration for the server, and then creating it. The server is going to use the binary protocol over TCP, and listen on port 4840.

  UA_ServerConfig config = UA_ServerConfig_standard;
  UA_ServerNetworkLayer nl = UA_ServerNetworkLayerTCP(UA_ConnectionConfig_standard, 4840);
  config.networkLayers = &nl;
  config.networkLayersSize = 1;
  UA_Server *server = UA_Server_new(config);

At this point, the server is created but it is not yet running. This is achieved by:

  UA_Server_run(server, &running);

The above code will stop the server whenever running becomes false. As we have seen above, the signal handler will update running.

Finally, we need to clean-up the resources:

UA_Server_delete(server);

The full example should look like:

#include <signal.h>
/* Include the OPC-UA open62541 header file */
#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;

  return;
};

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

  UA_ServerConfig config = UA_ServerConfig_standard;
  UA_ServerNetworkLayer nl = UA_ServerNetworkLayerTCP(UA_ConnectionConfig_standard, 4840);
  config.networkLayers = &nl;
  config.networkLayersSize = 1;
  UA_Server *server = UA_Server_new(config);
  
  UA_Server_run(server, &running);

  UA_Server_delete(server);
  
  return 0; 
  };

Adding Factory Robots

We now have a simple OPC-UA factory server running. Let's add some robots to our server as Object Nodes. Let's do this using object orientation so if there are other machines or stuff that we want to add to this factory server later it will be easier.

First lets add an a function for a Generic Object Node called objectType

UA_NodeId robotTypeId0 = {1, UA_NODEIDTYPE_NUMERIC, {1001}};

static void defineObjectTypes(UA_Server *server) {

  /* Define the object type for "Object" */

  UA_NodeId objectTypeId; 

  /* Set the Attributes for the Object */

  UA_ObjectTypeAttributes objectAttributes;

  UA_ObjectTypeAttributes_init(&objectAttributes);
  objectAttributes.displayName = UA_LOCALIZEDTEXT("en_US", "ObjectType");

  UA_Server_addObjectTypeNode(server, UA_NODEID_NULL,
                              UA_NODEID_NUMERIC(0, UA_NS0ID_BASEOBJECTTYPE),
			      UA_NODEID_NUMERIC(0, UA_NS0ID_HASSUBTYPE),
			      UA_QUALIFIEDNAME(1, "ObjectType"), objectAttributes,
			      NULL, &objectTypeId);

Now lets add some Object Nodes to the Object Node for various different objects in our factory.

/* Define the object type for "Robot 0" */

UA_ObjectTypeAttributes robotAttribute;

UA_ObjectTypeAttributes_init(&robotAttribute);
robotAttribute.displayName = UA_LOCALIZEDTEXT("en_US", "RobotType");

UA_Server_addObjectTypeNode(server, robotTypeId0,
                            objectTypeId,
                            UA_NODEID_NUMERIC(0, UA_NS0ID_HASSUBTYPE),
                            UA_QUALIFIEDNAME(1, "RobotType"),
                            robotAttribute,
                            NULL, NULL);

Let's add 2 Variable Nodes to our first Robot Object. One Variable will be the status (boolean) of the robot. The second Variable Node will represent some value associated with the robot, i.e. location or workload.

/* Define a variable type for "Robot 0" */

UA_VariableAttributes statusAttribute;

UA_VariableAttributes_init(&statusAttribute);
statusAttribute.displayName = UA_LOCALIZEDTEXT("en_US", "Status");
statusAttribute.valueRank = -1;

UA_NodeId statusId;

UA_Server_addVariableNode(server, UA_NODEID_NULL, robotTypeId0,
                          UA_NODEID_NUMERIC(0, UA_NS0ID_HASCOMPONENT),
                          UA_QUALIFIEDNAME(1, "Status"),
                          UA_NODEID_NULL, statusAttribute, NULL, &statusId);

/* Make the status variable mandatory */

UA_Server_addReference(server, statusId,
                       UA_NODEID_NUMERIC(0, UA_NS0ID_HASMODELLINGRULE),
                       UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_MODELLINGRULE_MANDATORY),
                       true);

/* Define another variable type for "Robot 0" */

UA_VariableAttributes workloadAttribute;

UA_VariableAttributes_init(&workloadAttribute);
workloadAttribute.displayName = UA_LOCALIZEDTEXT("en_US", "Workload");
workloadAttribute.valueRank = -1;

UA_NodeId workloadId;

UA_Server_addVariableNode(server, UA_NODEID_NULL,  robotTypeId0,
                          UA_NODEID_NUMERIC(0, UA_NS0ID_HASCOMPONENT),
                          UA_QUALIFIEDNAME(1, "Workload"),
                          UA_NODEID_NULL, workloadAttribute,
                          NULL, &workloadId);

/* Make the workload variable mandatory */

UA_Server_addReference(server, workloadId,    
                       UA_NODEID_NUMERIC(0, UA_NS0ID_HASMODELLINGRULE),
                       UA_EXPANDEDNODEID_NUMERIC(0,UA_NS0ID_MODELLINGRULE_MANDATORY),
                       true);

}

Now lets add a function to build the derived robot object node.

static void addRobotObject(UA_Server *server, char *name) {

  UA_ObjectAttributes objectAttribute;

  UA_ObjectAttributes_init(&objectAttribute);
  objectAttribute.displayName = UA_LOCALIZEDTEXT("en_US", name);

  UA_Server_addObjectNode(server, UA_NODEID_NULL,
			  UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
			  UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
			  UA_QUALIFIEDNAME(1, name),
			  robotTypeId0, /* this refers to the object type identifier */
			  objectAttribute, NULL, NULL);

    return;
};

In the main function lets create some robots.

int main (void) {

  signal(SIGINT, stopHandler);
  signal(SIGTERM, stopHandler);

  UA_ServerConfig config = UA_ServerConfig_standard;
  UA_ServerNetworkLayer nl = UA_ServerNetworkLayerTCP(UA_ConnectionConfig_standard, 4840);
  config.networkLayers = &nl;
  config.networkLayersSize = 1;
  UA_Server *server = UA_Server_new(config);
  
  defineObjectTypes(server);

  addRobotObject(server, "robot 0");
  addRobotObject(server, "robot 1");
  addRobotObject(server, "robot 2");
  addRobotObject(server, "robot 3");
  addRobotObject(server, "robot 4");
  addRobotObject(server, "robot 5");

  UA_Server_run(server, &running);

  UA_Server_delete(server);

  return 0;
}

The final code should look like this

#include <signal.h>
/* Include the OPC-UA open62541 header file */
#include "open62541.h"

UA_NodeId robotTypeId0 = {1, UA_NODEIDTYPE_NUMERIC, {1001}};

static void defineObjectTypes(UA_Server *server) {

  /* Define the object type for "Object" */

  UA_NodeId objectTypeId;

  /* Set the Attributes for the Object */

  UA_ObjectTypeAttributes objectAttributes;

  UA_ObjectTypeAttributes_init(&objectAttributes);
  objectAttributes.displayName = UA_LOCALIZEDTEXT("en_US", "ObjectType");

  UA_Server_addObjectTypeNode(server, UA_NODEID_NULL,
                              UA_NODEID_NUMERIC(0, UA_NS0ID_BASEOBJECTTYPE),
			      UA_NODEID_NUMERIC(0, UA_NS0ID_HASSUBTYPE),
			      UA_QUALIFIEDNAME(1, "ObjectType"), objectAttributes,
			      NULL, &objectTypeId);


  /* Define the object type for "Robot 0" */

  UA_ObjectTypeAttributes robotAttribute;

  UA_ObjectTypeAttributes_init(&robotAttribute);
  robotAttribute.displayName = UA_LOCALIZEDTEXT("en_US", "RobotType");

  UA_Server_addObjectTypeNode(server, robotTypeId0,
                              objectTypeId,
			      UA_NODEID_NUMERIC(0, UA_NS0ID_HASSUBTYPE),
			      UA_QUALIFIEDNAME(1, "RobotType"),
			      robotAttribute,
			      NULL, NULL);

  /* Define a variable type for "Robot 0" */

  UA_VariableAttributes statusAttribute;

  UA_VariableAttributes_init(&statusAttribute);
  statusAttribute.displayName = UA_LOCALIZEDTEXT("en_US", "Status");
  statusAttribute.valueRank = -1;

  UA_NodeId statusId;

  UA_Server_addVariableNode(server, UA_NODEID_NULL, robotTypeId0,
                            UA_NODEID_NUMERIC(0, UA_NS0ID_HASCOMPONENT),
			    UA_QUALIFIEDNAME(1, "Status"),
			    UA_NODEID_NULL, statusAttribute, NULL, &statusId);

  /* Make the status variable mandatory */

  UA_Server_addReference(server, statusId,
                         UA_NODEID_NUMERIC(0, UA_NS0ID_HASMODELLINGRULE),
			 UA_EXPANDEDNODEID_NUMERIC(0, UA_NS0ID_MODELLINGRULE_MANDATORY),
			 true);

  /* Define another variable type for "Robot 0" */

  UA_VariableAttributes workloadAttribute;

  UA_VariableAttributes_init(&workloadAttribute);
  workloadAttribute.displayName = UA_LOCALIZEDTEXT("en_US", "Workload");
  workloadAttribute.valueRank = -1;

  UA_NodeId workloadId;

  UA_Server_addVariableNode(server, UA_NODEID_NULL, robotTypeId0,
                            UA_NODEID_NUMERIC(0, UA_NS0ID_HASCOMPONENT),
			    UA_QUALIFIEDNAME(1, "Workload"),
			    UA_NODEID_NULL, workloadAttribute,
			    NULL, &workloadId);

  /* Make the workload variable mandatory */

  UA_Server_addReference(server, workloadId,    
                         UA_NODEID_NUMERIC(0, UA_NS0ID_HASMODELLINGRULE),
			 UA_EXPANDEDNODEID_NUMERIC(0,UA_NS0ID_MODELLINGRULE_MANDATORY),
			 true);
  return;
};

static void addRobotObject(UA_Server *server, char *name) {

  UA_ObjectAttributes objectAttribute;

  UA_ObjectAttributes_init(&objectAttribute);
  objectAttribute.displayName = UA_LOCALIZEDTEXT("en_US", name);

  UA_Server_addObjectNode(server, UA_NODEID_NULL,
			  UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER),
			  UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES),
			  UA_QUALIFIEDNAME(1, name),
			  robotTypeId0, /* this refers to the object type identifier */
			  objectAttribute, NULL, NULL);

    return;
};

UA_Boolean running = true;

static void stopHandler(int sig) {

  UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "received ctrl-c");

  running = false;

  return;
};

int main (void) {

  signal(SIGINT, stopHandler);
  signal(SIGTERM, stopHandler);

  UA_ServerConfig config = UA_ServerConfig_standard;
  UA_ServerNetworkLayer nl = UA_ServerNetworkLayerTCP(UA_ConnectionConfig_standard, 4840);
  config.networkLayers = &nl;
  config.networkLayersSize = 1;
  UA_Server *server = UA_Server_new(config);

  defineObjectTypes(server);

  addRobotObject(server, "robot 0");
  addRobotObject(server, "robot 1");
  addRobotObject(server, "robot 2");
  addRobotObject(server, "robot 3");
  addRobotObject(server, "robot 4");
  addRobotObject(server, "robot 5");

  UA_Server_run(server, &running);

  UA_Server_delete(server);

  return 0;
};

Now that we have a server running with some information in some nodes. Let's build a client to query the server.

Client to Find OPC-UA Endpoints

Now let's implement the client side. A minimal client to see if there are any endpoints to query would look like this:

#include <stdio.h>
/* Include the OPC-UA open62541 header file */
#include "open62541.h"

int main(void) {

    UA_Client *client = UA_Client_new(UA_ClientConfig_standard);

    /* List the endpoints that are found */

    UA_EndpointDescription* endpointArray = NULL;

    size_t endpointArraySize = 0;

    UA_StatusCode retval = UA_Client_getEndpoints(client,
						  "opc.tcp://localhost:4840",
						  &endpointArraySize,
						  &endpointArray);

    /* If the connection fails delete the client and return */
    if(retval != UA_STATUSCODE_GOOD) {

        UA_Array_delete(endpointArray,
			endpointArraySize,
			&UA_TYPES[UA_TYPES_ENDPOINTDESCRIPTION]);

	UA_Client_delete(client);

	return (int)retval;

    };

    /* Print out the endpoints found in the connection */

    printf("%i endpoints found\n", (int)endpointArraySize);

    for(size_t i=0;i<endpointArraySize;i++){

      printf("URL of endpoint %i is %.*s\n", (int)i,
               (int)endpointArray[i].endpointUrl.length,
               endpointArray[i].endpointUrl.data);
    };

    /* Delete the endpoints after they have been discovered */

    UA_Array_delete(endpointArray,
		    endpointArraySize,
		    &UA_TYPES[UA_TYPES_ENDPOINTDESCRIPTION]);


    /* Disconnects the client internally */

    UA_Client_delete(client);

    return UA_STATUSCODE_GOOD;
}

The first block creates a client with the same configuration as the server, and then tries to connect to it. Then it checks for the endpoints, and if an error occurs, it exits.

We will include our client code immediately after the connection is established.

A second block of code that will take care of freeing up the resources and returning the error code is also introduced.

This example can already be compiled by running:

# Alternatively, you can use the Makefile to handle compilation.
$ gcc client.c open62541.c -o client

A client browsing nodes

Information in OPC-UA is modeled as a hierarchy of nodes. Let's write some code to browse the nodes on the server we just wrote.

/* Connect to the local server */

retval = UA_Client_connect(client, "opc.tcp://localhost:4840");

/* If the connection fails delete the client and return */

if(retval != UA_STATUSCODE_GOOD) {

    UA_Client_delete(client);

    return (int)retval;
};

/* Browse for some objects */

printf("Browsing nodes in objects folder:\n");

UA_BrowseRequest browseRequest;
UA_BrowseRequest_init(&browseRequest);

browseRequest.requestedMaxReferencesPerNode = 0;
browseRequest.nodesToBrowse = UA_BrowseDescription_new();
browseRequest.nodesToBrowseSize = 1;
browseRequest.nodesToBrowse[0].nodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);

/* Ask to return all nodes */

browseRequest.nodesToBrowse[0].resultMask = UA_BROWSERESULTMASK_ALL;

UA_BrowseResponse browseResponse = UA_Client_Service_browse(client, browseRequest);

/* Print out the results */

printf("%-9s %-16s %-16s %-16s\n", "NAMESPACE", "NODEID", "BROWSE NAME", "DISPLAY NAME");

for(size_t i = 0; i < browseResponse.resultsSize; ++i) {

  for(size_t j = 0; j < browseResponse.results[i].referencesSize; ++j) {

UA_ReferenceDescription *reference = &(browseResponse.results[i].references[j]);

if(reference->nodeId.nodeId.identifierType == UA_NODEIDTYPE_NUMERIC) {

printf("%-9d %-16d %-16.*s %-16.*s\n",
 reference->nodeId.nodeId.namespaceIndex,
 reference->nodeId.nodeId.identifier.numeric, (int)reference->browseName.name.length,
 reference->browseName.name.data, (int)reference->displayName.text.length,
 reference->displayName.text.data);

} else if(reference->nodeId.nodeId.identifierType == UA_NODEIDTYPE_STRING) {

printf("%-9d %-16.*s %-16.*s %-16.*s\n",
 reference->nodeId.nodeId.namespaceIndex,
 (int)reference->nodeId.nodeId.identifier.string.length,
 reference->nodeId.nodeId.identifier.string.data,
 (int)reference->browseName.name.length, reference->browseName.name.data,
 (int)reference->displayName.text.length, reference->displayName.text.data);

};


  };

};

/* Clean up */

UA_BrowseRequest_deleteMembers(&browseRequest);

UA_BrowseResponse_deleteMembers(&browseResponse);

The final program should look like this

#include <stdio.h>
/* Include the OPC-UA open62541 header file */
#include "open62541.h"

int main(void) {

    UA_Client *client = UA_Client_new(UA_ClientConfig_standard);

    /* List the endpoints that are found */

    UA_EndpointDescription* endpointArray = NULL;

    size_t endpointArraySize = 0;

    UA_StatusCode retval = UA_Client_getEndpoints(client,
						  "opc.tcp://localhost:4840",
						  &endpointArraySize,
						  &endpointArray);

    /* If the connection fails delete the client and return */
    if(retval != UA_STATUSCODE_GOOD) {

        UA_Array_delete(endpointArray,
			endpointArraySize,
			&UA_TYPES[UA_TYPES_ENDPOINTDESCRIPTION]);

	UA_Client_delete(client);

	return (int)retval;

    };

    /* Print out the endpoints found in the connection */

    printf("%i endpoints found\n", (int)endpointArraySize);

    for(size_t i=0;i<endpointArraySize;i++){

      printf("URL of endpoint %i is %.*s\n", (int)i,
               (int)endpointArray[i].endpointUrl.length,
               endpointArray[i].endpointUrl.data);
    };

    /* Delete the endpoints after they have been discovered */

    UA_Array_delete(endpointArray,
		    endpointArraySize,
		    &UA_TYPES[UA_TYPES_ENDPOINTDESCRIPTION]);

    /* Connect to the local server */

    retval = UA_Client_connect(client, "opc.tcp://localhost:4840");

    /* If the connection fails delete the client and return */

    if(retval != UA_STATUSCODE_GOOD) {

        UA_Client_delete(client);

        return (int)retval;
    };

    /* Browse for some objects */

    printf("Browsing nodes in objects folder:\n");

    UA_BrowseRequest browseRequest;
    UA_BrowseRequest_init(&browseRequest);

    browseRequest.requestedMaxReferencesPerNode = 0;
    browseRequest.nodesToBrowse = UA_BrowseDescription_new();
    browseRequest.nodesToBrowseSize = 1;
    browseRequest.nodesToBrowse[0].nodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);

    /* Ask to return all nodes */

    browseRequest.nodesToBrowse[0].resultMask = UA_BROWSERESULTMASK_ALL;

    UA_BrowseResponse browseResponse = UA_Client_Service_browse(client, browseRequest);

    /* Print out the results */

    printf("%-9s %-16s %-16s %-16s\n", "NAMESPACE", "NODEID", "BROWSE NAME", "DISPLAY NAME");

    for(size_t i = 0; i < browseResponse.resultsSize; ++i) {

      for(size_t j = 0; j < browseResponse.results[i].referencesSize; ++j) {

	UA_ReferenceDescription *reference = &(browseResponse.results[i].references[j]);

	if(reference->nodeId.nodeId.identifierType == UA_NODEIDTYPE_NUMERIC) {

	  printf("%-9d %-16d %-16.*s %-16.*s\n",
		 reference->nodeId.nodeId.namespaceIndex,
		 reference->nodeId.nodeId.identifier.numeric, (int)reference->browseName.name.length,
		 reference->browseName.name.data, (int)reference->displayName.text.length,
		 reference->displayName.text.data);

	} else if(reference->nodeId.nodeId.identifierType == UA_NODEIDTYPE_STRING) {

	  printf("%-9d %-16.*s %-16.*s %-16.*s\n",
		 reference->nodeId.nodeId.namespaceIndex,
		 (int)reference->nodeId.nodeId.identifier.string.length,
		 reference->nodeId.nodeId.identifier.string.data,
		 (int)reference->browseName.name.length, reference->browseName.name.data,
		 (int)reference->displayName.text.length, reference->displayName.text.data);

	};


      };

    };

    /* Clean up */

    UA_BrowseRequest_deleteMembers(&browseRequest);

    UA_BrowseResponse_deleteMembers(&browseResponse);

    /* Disconnects the client internally */

    UA_Client_delete(client);

    return UA_STATUSCODE_GOOD;
}

Putting it all together

Open a terminal and run the server:

$ ./server
[11/16/2017 23:54:17.588] info/network	TCP network layer listening on opc.tcp://nucuser-desktop:4840

Now open another terminal and run the client:

$ ./client
1 endpoints found
URL of endpoint 0 is opc.tcp://localhost:4840
Browsing nodes in objects folder:
NAMESPACE NODEID           BROWSE NAME      DISPLAY NAME    
0         61               FolderType       FolderType      
0         2253             Server           Server          
1         118              robot 0          robot 0         
1         121              robot 1          robot 1         
1         124              robot 2          robot 2         
1         127              robot 3          robot 3         
1         130              robot 4          robot 4         
1         133              robot 5          robot 5

Congratulations! You just made your client-server application work.

Additional Information