Allen Bradley Micro 820 PLC

I don't think a wireshark log from me is going to help you much. What would be more interesting is you posting wireshark capture. Though, I think it won't reveal much since you are getting a connection timeout. This usually means that you computer sent a packet, which would be the register session and the Ethernet module in you control logix either didn't receive it, or didn't respond.

Did you disable all other network adapters like I suggested? This would eliminate the possibility that python is using the wrong adapter.

Edit: one possibility is you need to add a firewall exception for python or tcp port 44818. Maybe the firewall is blocking outgoing or incoming data.
 
dmroeder said:
I don't think a wireshark log from me is going to help you much. What would be more interesting is you posting wireshark capture. Though, I think it won't reveal much since you are getting a connection timeout. This usually means that you computer sent a packet, which would be the register session and the Ethernet module in you control logix either didn't receive it, or didn't respond.

Did you disable all other network adapters like I suggested? This would eliminate the possibility that python is using the wrong adapter.

Edit: one possibility is you need to add a firewall exception for python or tcp port 44818. Maybe the firewall is blocking outgoing or incoming data.
Click to expand...

Hi,

I tried to disable other network adapter and test but still the problem persists. I just wanted to compare the packet of control logix PLC and Micro 800 PLC. For Micro 800 PLC I am able to collect traces at my end but unfortunately for Control Logix I am not able to do. If I can get wireshark logs for control logix then it would be easier for me to analyze and compare both the logs.

Thanks
 
Need 1 more clarification regarding Read/Write request used in pylogix driver.
Whether Unconnected CIP message is being used for reading or writing tag value. Reason why I am asking this question is because I have used unconnected send with Control Logix PLC.
 
dmroeder said:
I don't think a wireshark log from me is going to help you much. What would be more interesting is you posting wireshark capture. Though, I think it won't reveal much since you are getting a connection timeout. This usually means that you computer sent a packet, which would be the register session and the Ethernet module in you control logix either didn't receive it, or didn't respond.

Did you disable all other network adapters like I suggested? This would eliminate the possibility that python is using the wrong adapter.

Edit: one possibility is you need to add a firewall exception for python or tcp port 44818. Maybe the firewall is blocking outgoing or incoming data.
Click to expand...

Hi dmroeder,

I tried to capture wireshark logs while reading tag from Control Logix PLC using pylogix driver. I can see "Service not supported for Large Forward Open". I am attaching screenshot of wireshark log for your reference. Please share your inputs if there is any way to resolve the problem.

Thanks

ControlLogixError.PNG
 
That's normal for an older module like a ENET, maybe even ENBT or older controllers.

Pylogix tries to make the connection with the larger packet size, if it is not successful, it falls back to the smaller packet size, which is supported by all Logix controllers/Ethernet modules. What did the next few packets look like?

If you add "ENIP" in the filter, it will filter out non Ethernet I/P/CIP packets.
 
dmroeder said:
That's normal for an older module like a ENET, maybe even ENBT or older controllers.

Pylogix tries to make the connection with the larger packet size, if it is not successful, it falls back to the smaller packet size, which is supported by all Logix controllers/Ethernet modules. What did the next few packets look like?

If you add "ENIP" in the filter, it will filter out non Ethernet I/P/CIP packets.
Click to expand...

I tried to filter out and see the traces in wireshark. It is trying to re-transmit the packet and getting timed out. I am attaching trace screenshot for your reference. Please give your suggestions.

ControlLogixError1.PNG
 
dmroeder said:
Hmm. Try adding a line comm.ConnectionSize = 508
Click to expand...

Thanks for the suggestion.
After making the changes, it is connecting now and I am able to read tag of control logix PLC. I believe that connected send is used for control logix as well in pylogix driver.

Actually in my application I have used unconnected send with control logix PLC and it is working properly. I was looking to make modification in the same application and make use of unconnected send with Micro 800 series PLC. Can you help me in providing any reference for unconnected send for Micro 800 PLC (wireshark log or any technical document) which I can refer to make modification in my application to support Micro 800 series PLC with unconnected send.

Thanks
 
Tasneem Ahmad said:
Thanks for the suggestion.
After making the changes, it is connecting now and I am able to read tag of control logix PLC. I believe that connected send is used for control logix as well in pylogix driver.

Actually in my application I have used unconnected send with control logix PLC and it is working properly. I was looking to make modification in the same application and make use of unconnected send with Micro 800 series PLC. Can you help me in providing any reference for unconnected send for Micro 800 PLC (wireshark log or any technical document) which I can refer to make modification in my application to support Micro 800 series PLC with unconnected send.

Thanks
Click to expand...

Hi dmroeder,

Can you please share your inputs on the quoted query made earlier. I am actually stuck with unconnected send implementation for Micro 800.
It would be great if you can provide any help with respect to wireshark log or any document which defines the packet to be used for unconnected send.

Thanks in advance.
 
dmroeder said:
It's using connected send. For clarity, I us pylogix with control logix almost every day.
Click to expand...

Hi dmroeder,

Can you please help me in providing below information with respect to Micro 870 PLC. I am trying to send Command: Send RR Data (0x006f) but I am seeing error in the wireshark log. It looks like it is due to highlighted values being used in the wireshark log being attached.

Please share your inputs.

RoutePath.JPG
 
dmroeder said:
It's not that those values are incorrect and need to be changed, I think you need to remove them completely.
Click to expand...

Hi dmroeder,

I tried to remove those fields while sending packet to Micro 870 PLC. After removing I am getting malformed. Please find the attached screenshot.
Looks like those fields are required as per CIP Protocol.

Please share your inputs after checking the screenshot. Thanks

MalformedPacket.PNG
 
I'm not 100% sure, I don't use unconnected sends like this. You could try adding the pad byte back in and the route path size byte, with a value of 0.
 

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