The function block for remote OPC UA communication reading and writing keeps reporting errors.

[songshuqi1]

I attempted to set up the system by referring to the OPC UA documentation. However, some of the modules in the document lacked RD interfaces and others lacked SD interfaces. The 2.0.1 version I downloaded had all these interfaces, but it still reported errors. Even deleting the interfaces continued to cause errors. It seems that deleting the interfaces doesn't work, so which module should I use for reading and writing in OPC UA?

[azoitl]

The problem is that when you read or write single values you need the two number Client blocks. because you need either one without inputs or outputs. I created this PR #750 for the upcoming 3.0 release.

Please also note that we are in the final phase of the 3.0 release cycle. We improved many things for the 3.0 release especially also our OPC UA support. Therefore I woulds strongly encourage you to use the 3.0 early access version for your tests. you can find more information here: https://eclipse.dev/4diac/news/2025/2025/eclipse-4diac-3.0-enters-feature-freeze/

[songshuqi1]

Hello, I have another question. After configuring the module by myself, how should I set the ID? When I configure it, I can't read the nodes. How should I configure the specific nodes? Could you please help me solve this problem?

[songshuqi1]

Hello, I have another question. After configuring the module by myself, how should I set the ID? When I configure it, I can't read the nodes. How should I configure the specific nodes? Could you please help me solve this problem?

[azoitl]

please follow the description in our documentation. There the rules for browsepaths are rather clearly specified.

[songshuqi1]

I'm still unable to get the test program to work after setting it up according to the official website. Could you please take a look and help me out?




Originally, the CLIENT module set up according to the official website didn't work, but the LOCAL SUNSCRIBE did work. They said that my CLIENT couldn't find the node. How do you set the node? The screenshot I provided is what I have been trying. Thank you very much for your help! This problem has been stuck here for a long time and cannot be resolved.

[azoitl]

You are trying to create and access elements in the root node of the information model. AFAIK you need to put your instances under Objects. Have you tried to just copy paste the values from the documentation. These are known to work. For your object Flop this would then be: opc_ua[WRITE;/Objects/1:Flop].

[songshuqi1]

Thank you very much for your help. When I was conducting remote OPCUA communication, I created a server program in Python and accessed it using the 4diac module. When I named the IDs in this format, I couldn't access the nodes.


Therefore, I changed the ID settings. However, when using this new configuration, I encountered the same error as before.


I would like to ask you, what's going on here? My Python program has already defined the nodes. This is my Python program.

from opcua import Server
from datetime import datetime
import time
from opcua import ua

def main():
server = Server()
server.set_endpoint("opc.tcp://172.16.4.125:4940/")
server.set_server_name("4diac OPC UA Server - Int16")
uri = "http://4diac.example.org"
idx = server.register_namespace(uri)
print(f"Registered namespace: {uri} with index: {idx}")

objects = server.get_objects_node()

writable_var = objects.add_variable(
    ua.NodeId(3, 1), 
    "WritableVariable", 
    0,  
    varianttype=ua.VariantType.Int16  
writable_var.set_writable(True)


read_only_var = objects.add_variable(
    ua.NodeId(2, 1), 
    "ReadOnlyVariable", 
    0, 
    varianttype=ua.VariantType.Int16  
)
read_only_var.set_writable(False)


server.start()
print("Server started at {}".format(server.endpoint))
print("Available nodes:")
print("- WritableVariable: ns=1;i=3 (Int16, Writable)")
print("- ReadOnlyVariable: ns=1;i=2 (Int16, ReadOnly)")
print("Waiting for client connections...")

try:
    count = 0
    while True:
        count = (count + 1) % 32767
        read_only_var.set_value(ua.Variant(count, ua.VariantType.Int16))
        
        writable_value = writable_var.get_value()
        print(f"Time: {datetime.now().strftime('%H:%M:%S')} | Client wrote: {writable_value} | Counter: {count}")

        time.sleep(1)
        
except KeyboardInterrupt:
    print("Server stopped by user")
except Exception as e:
    print(f"Server error: {e}")
finally:
    server.stop()
    print("Server stopped")

if name == "main":
main()

[azoitl]

I always found it quite helpfull to use a generic client like UA Expert to connect to a server, browse it and see the names and paths of the variable. I guess this could also help you to find the right parameters for your 1499 application.

[songshuqi1]

Hello, I'm currently trying out the 3.0 version of 4diac. However, when I was testing OPCUA, I encountered this error regarding the data type. But I was creating a node, so is this a change in the new version's operation? Do you have a user manual? Also, the startup command has changed to something like './forte -c 202.118.21.5:61499', is this correct? I'm really confused now.

[songshuqi1]

Also, regarding the OPCUA support in 4diac 3.0, could it be a version issue?

[azoitl]

If the client tries to communicate with your publisher from your first picture I see that there you are creating a variable of type DINT and you would like to read an INT. This is a mismatch and therefore the CLIENT is not happy.