exception with plc_read using pylogix 1.0.5 #257
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Comments
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Thanks, I'll check this out as soon as I can |
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@ChristopheLaurent, I have a solution for this that is almost complete. |
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@ChristopheLaurent, if you can try the branch bugfix/large-list-read, that would be helpful. |
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Hello,
I fetched this branch, copy and paste the pylogix folder in my code and removed pylogix requirements.
Unfortunately I still have the same problem:
groot-svc | Exception reading 405 tags from 192.168.22.10: unpack_from requires a buffer of at least 49 bytes for unpacking 1 bytes at offset 48 (actual buffer size is 24)
groot-svc | File "/opt/everest/dev-ts-groot/groot_lib.py", line 159, in plc_read
groot-svc | results = comm.Read(batch)
groot-svc | File "/opt/everest/dev-ts-groot/pylogix/eip.py", line 126, in Read
groot-svc | return self._batch_read(tag)
groot-svc | File "/opt/everest/dev-ts-groot/pylogix/eip.py", line 393, in _batch_read
groot-svc | responses += [Response(tag, value, status) for tag, value, status in self._multi_read(current_requests)]
groot-svc | File "/opt/everest/dev-ts-groot/pylogix/eip.py", line 428, in _multi_read
groot-svc | status, ret_data = self.conn.send(request)
groot-svc | File "/opt/everest/dev-ts-groot/pylogix/lgx_comm.py", line 69, in send
groot-svc | return self._get_bytes(eip_header, connected)
groot-svc | File "/opt/everest/dev-ts-groot/pylogix/lgx_comm.py", line 177, in _get_bytes
groot-svc | status = unpack_from('<B', ret_data, 48)[0]
However, the call stack is not exactly the same as before.
Thanks a lot for your help, please let me know if you want me to check something else.
Best regards,
Christophe
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Could I convince you to capture it with wireshark and email the capture to me? |
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I'm experiencing the same issue. Grabbing 5 tags sequentially, my program outputs: But trying to grab them all in a batch using I subclassed class DebugPLC(PLC):
def _parse_multi_read(self, data, tags):
"""
Extract the values from the multi-service message reply
"""
print("Entering _parse_multi_read")
print(f"Raw data received: {data!r}") # Print raw data for inspection
data = data[46:]
print(f"Data after removing header (46 bytes): {data!r}")
try:
service = unpack_from("<H", data, 0)[0]
print(f"Service code: {service}")
status, ext_status = unpack_from("<BB", data, 2)
print(f"Status: {status}, Extended Status: {ext_status}")
service_count = unpack_from("<H", data, 4)[0]
print(f"Service count: {service_count}")
offsets = [
unpack_from("<H", data, i * 2 + 6)[0] for i in range(service_count)
]
print(f"Offsets: {offsets}")
# Adjust offsets to be relative to data start (after header)
data_start = (
4 + service_count * 2 + 2
) # 4 (header) + service_count * 2 (offsets) + 2 (service count)
offsets = [offset - data_start for offset in offsets]
print(f"Adjusted offsets (relative to data start): {offsets}")
data = data[data_start:]
print(f"Data after offset adjustment: {data!r}")
reply = []
current_offset = 0
for idx, tag_info in enumerate(tags):
print(f"\nProcessing tag: {tag_info[0]}")
tag_name, base_tag, index = parse_tag_name(tag_info[0])
element_count = tag_info[1]
# Determine segment end based on next offset or end of data
if idx + 1 < len(offsets):
segment_end = offsets[idx + 1]
else:
segment_end = len(data)
segment = data[current_offset:segment_end]
print(f"Segment for tag: {segment!r}")
current_offset = segment_end
segment_service = unpack_from("<H", segment, 0)[0]
print(f"Segment service: {segment_service}")
segment_status = unpack_from("<B", segment, 2)[0]
print(f"Segment status: {segment_status}")
if segment_status == 6:
print("Segment status is 6 (partial), attempting to read more data")
segment_data_type = unpack_from("<B", segment, 4)[0]
ioi = self._build_ioi(tag_name, segment_data_type)
self.Offset = len(segment) - 8
request = self._add_partial_read_service(ioi, element_count)
segment_status, ret_data = self.conn.send(request)
print(f"Partial read status: {segment_status}, data: {ret_data!r}")
segment += ret_data[54:]
if segment_status == 0:
print("Segment status is 0 (success)")
segment_data_type = unpack_from("<B", segment, 4)[0]
print(f"Segment data type: {segment_data_type}")
self.KnownTags[base_tag] = (segment_data_type, 0)
if segment_data_type == 0xA0: # String
print("Parsing string value")
value = self._parse_string_value(segment)
elif segment_data_type == 0xC4: # DINT (for counters)
print("Parsing DINT value")
value = self._parse_dint_values(segment)
elif segment_data_type == 0xD3 or bit_of_word(
tag_name
): # BOOL Array or Bit of Word
print("Parsing BOOL array or bit of word")
values = self._parse_bool_values(segment, segment_data_type)
value = self._words_to_bits(tag_name, values, element_count)
else:
print("Parsing other value type")
value = self._parse_other_values(segment, segment_data_type)
else:
print(
f"Segment status is not 0, setting value to None. Status: {segment_status}"
)
value = None
# value shouldn't be a list if there is only one
if isinstance(value, list) and len(value) == 1:
value = value[0]
response = [tag_name, value, segment_status]
reply.append(response)
print("\nExiting _parse_multi_read")
return reply
except Exception as e:
print(f"ERROR in _parse_multi_read: {e}")
raiseAnd here's its output: Thanks for working on this! And let me know if I can help you with any more information on diagnosing the problem. |
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Hmm, I can see this being an issue when including types that are not the basic data types (STRUCTs). @ChristopheLaurent, do you also have tags that are structures/UDT's? I'll need to do some more testing... |
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I could email you my WireShark capture, if that would be helpful. Where should I send it to? |
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My user name at gmail |
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I think that the root cause of my issue is not _parse_multi_read but _multi_read. I modified _multi_read as follow: The resulting trace shows that the first call to multi_read works fine: Then the second call looks completely different with the 1st service that generate a huge request : Eventually I get the same exception as before. How the service #0 can have 400 tags in the second call to _multi_read, instead of 20 in the 1st call to _multi_read ? Possibly @ammonwk had a related but different issue ? |
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I'm working on a fix. The issue has to do with not taking into account the size of structs when trying to unpack the multi-message request. Apologies for the issue, I'll have it fixed as soon as I can. |
No worries, this is not an emergency for us, we can stay on version 0.8 for the time being. Furthermore I won't be able to test your fix before the 18th of December. Thanks a lot for your support ! |
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@ammonwk, are you able to run the lates changes on the bugfix branch? |
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Thanks for your work on this! It sort of works for me now, I'll give you
the details:
A little testing/proof of concept script:
Individual Reading (not batched)
Attempting to connect to PLC at 10.1.18.132...
Successfully connected to PLC!
PLC Time: 2024-12-16 20:19:52.154345
Reading tag structure...
=== Available Tags ===
Found 2951 tags
Attempting to read the tag Program:Preinspection.PreInspect
Result: Program:Preinspection.PreInspect
b'\x01\x00\x00\x00"\xe3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\xef\xdf\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\xc7\x00\x00\x00\x01\x00\x00\x00\x1a\x00\x00\x00\x01\x00\x00\x00%\xa3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00%\xa3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\x87\x00\x00\x00\x01\x00\x00\x00"\x00\x00\x00\x00\x00\x000\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00V2Z\x00\x00\x00\x00\x00\x00\x00\x00\x00\n\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xe5,\x10\xc0`\xea\x00\x00\xc1)\x00\x00\x00\x00\x00\x00\xc0\xf1\xff\x7f\x00\x00\x00\x00/\xb7\x0b\x00\xc0\xf1\xff\x7f\xdf\xfa"\x00\xe5,\x10\xa0\xc0\xf1\xff\x7f\xc0\xf1\xff\x7f\xe5,\x10\xa0\x90\x01\x00\x00\x90\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1f\x00\x00\x00Wt\xff\xff\x1a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00d\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xb2*\x10\x00\xfa\x00\x00\x00\x00\x00\x00\x00!\xb4\x0f\x00k\x03\x00\x00\x00\x00\x00\x00\xb3*\x10\x00\xa4\x06\x00\x00\x00\x00\x00\x00\xf6\xba\x0f\x00A\n\x00\x00\x00\x00\x00\x00\xe5,\x10\xc0,\x01\x00\x00\x9c\x00\x00\x00U*\x10\x00\xf4\x01\x00\x00\x00\x00\x00\x00c\xc2\x0f\x00\xf4\x01\x00\x00\x00\x00\x00\x00\xe7*\x10\x002\x00\x00\x00\x00\x00\x00\x00I,\x10\x00\x88\x13\x00\x00\x00\x00\x00\x00\xa1)\x10\x00\xc8\x00\x00\x00\x00\x00\x00\x00\xe5,\x10\xc0\x98:\x00\x001\x02\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x98:\x00\x00\x81\x00\x04\x13'
Success
Attempting to read the tag
Program:Preinspection.Preinspect_Fail_Full_Light_Off
Result: Program:Preinspection.Preinspect_Fail_Full_Light_Off
b'\x96[)\x00\xfa\x00\x00\x00\x00\x00\x00\x00' Success
Attempting to read the tag
Program:Preinspection.Preinspect_Fail_Full_Light_On
Result: Program:Preinspection.Preinspect_Fail_Full_Light_On
b'd\xc2\x0f\x00\xfa\x00\x00\x00\x00\x00\x00\x00' Success
Attempting to read the tag Program:Preinspection.PreinspectGoodPartsCounter
Result: Program:Preinspection.PreinspectGoodPartsCounter
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' Success
Batched Reading (same tags)
Attempting to connect to PLC at 10.1.18.132...
Successfully connected to PLC!
PLC Time: 2024-12-16 20:20:17.429085
Reading tag structure...
=== Available Tags ===
Found 2951 tags
Attempting to read the tags ['Program:Preinspection.PreInspect',
'Program:Preinspection.Preinspect_Fail_Full_Light_Off',
'Program:Preinspection.Preinspect_Fail_Full_Light_On',
'Program:Preinspection.PreinspectGoodPartsCounter'] in a batch
comm.Read(['Program:Preinspection.PreInspect',
'Program:Preinspection.Preinspect_Fail_Full_Light_Off',
'Program:Preinspection.Preinspect_Fail_Full_Light_On',
'Program:Preinspection.PreinspectGoodPartsCounter'])
Result: [Response(TagName=Program:Preinspection.PreInspect,
Value=b'"\xe3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\xef\xdf\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\xc7\x01\x00\x00\x01\x00\x00\x00&\x00\x00\x00\x01\x00\x00\x00%\xa3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00%\xa3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\x87\x01\x00\x00\x01\x00\x00\x00\x1e\x00\x00\x00\x00\x00\x000\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00h2Z\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x9a\x8f\x10\xc0`\xea\x00\x00v\x8c\x00\x00\x00\x00\x00\x00\xc0\xf1\xff\x7f\x00\x00\x00\x00/\xb7\x0b\x00\xc0\xf1\xff\x7f\xdf\xfa"\x00`\x8c\x10
\xc0\xf1\xff\x7f\xc0\xf1\xff\x7f`\x8c\x10\x00\x90\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1f\x00\x00\x00Wt\xff\xff\x1a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00d\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xae\x89\x10\x00\xfa\x00\x00\x00\x00\x00\x00\x00!\xb4\x0f\x00k\x03\x00\x00\x00\x00\x00\x00\xaf\x89\x10\x00\xa4\x06\x00\x00\x00\x00\x00\x00\xf6\xba\x0f\x00A\n\x00\x00\x00\x00\x00\x00\x9a\x8f\x10\xa0,\x01\x00\x00,\x01\x00\x00\xf5\x7f\x10\x00\xf4\x01\x00\x00\x00\x00\x00\x00c\xc2\x0f\x00\xf4\x01\x00\x00\x00\x00\x00\x00\xe3\x89\x10\x002\x00\x00\x00\x00\x00\x00\x005\x8b\x10\x00\x88\x13\x00\x00\x00\x00\x00\x00\x9a\x8f\x10\xa0\xc8\x00\x00\x00\xc8\x00\x00\x00\x9a\x8f\x10\xc0\x98:\x00\x00\xea\x05\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x98:\x00\x00\xc1\x00\x04\x13',
Status=Success),
Response(TagName=Program:Preinspection.Preinspect_Fail_Full_Light_Off,
Value=b'\xfa\x00\x00\x00\x00\x00\x00\x00', Status=Success),
Response(TagName=Program:Preinspection.Preinspect_Fail_Full_Light_On,
Value=b'\xfa\x00\x00\x00\x00\x00\x00\x00', Status=Success),
Response(TagName=Program:Preinspection.PreinspectGoodPartsCounter,
Value=b'\x00\x00\x00\x00\x00\x00\x00\x00', Status=Success)]
Where the library might need better error handling:
If I iterate through all the tags.TagName to fetch them all, some result in
(None, Privilege violation), because they don't have a value to read:
Individual Reading ( Privilege violation )
Attempting to connect to PLC at 10.1.18.132...
Successfully connected to PLC!
PLC Time: 2024-12-16 20:19:38.582386
Reading tag structure...
=== Available Tags ===
Found 2951 tags
Attempting to read the tag Program:Preinspection
Result: Program:Preinspection None Privilege violation
Attempting to read the tag Program:Preinspection.PreInspect
Result: Program:Preinspection.PreInspect
b'\x01\x00\x00\x00"\xe3\x01\x00\xe8\x03\x00\x00\x00\x00\x00\x00\xef\xdf\x01\x00\xe8\...etc.
Success
Batched Reading ( Privilege violation )
Attempting to connect to PLC at 10.1.18.132...
Successfully connected to PLC!
PLC Time: 2024-12-16 20:18:30.836586
Reading tag structure...
=== Available Tags ===
Found 2951 tags
Attempting to read the tags ['Program:Preinspection',
'Program:Preinspection.PreInspect'] in a batch
comm.Read(['Program:Preinspection', 'Program:Preinspection.PreInspect'])
Traceback (most recent call last):
File "c:\Users\KAmmon\OneDrive - Ultradent Products
Inc\Documents\Scripts\data_analytics\tags_from_rockwell_batched.py", line
84, in <module>
connect_and_browse_plc(PLC_IP, PLC_SLOT)
~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
File "c:\Users\KAmmon\OneDrive - Ultradent Products
Inc\Documents\Scripts\data_analytics\tags_from_rockwell_batched.py", line
52, in connect_and_browse_plc
batch_read_results = comm.Read(tag_names_to_read)
File
"C:\Users\KAmmon\AppData\Local\Programs\Python\Python313\Lib\site-packages\pylogix\eip.py",
line 126, in Read
return self._batch_read(tag)
~~~~~~~~~~~~~~~~^^^^^
File
"C:\Users\KAmmon\AppData\Local\Programs\Python\Python313\Lib\site-packages\pylogix\eip.py",
line 376, in _batch_read
self._get_unknown_types(tags)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File
"C:\Users\KAmmon\AppData\Local\Programs\Python\Python313\Lib\site-packages\pylogix\eip.py",
line 1394, in _get_unknown_types
self._multi_read(unk_tags)
~~~~~~~~~~~~~~~~^^^^^^^^^^
File
"C:\Users\KAmmon\AppData\Local\Programs\Python\Python313\Lib\site-packages\pylogix\eip.py",
line 434, in _multi_read
response.extend(self._parse_multi_read_response(ret_data, new_tags[i]))
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
File
"C:\Users\KAmmon\AppData\Local\Programs\Python\Python313\Lib\site-packages\pylogix\eip.py",
line 1495, in _parse_multi_read_response
data_type = unpack_from("<B", segment, 4)[0]
~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
struct.error: unpack_from requires a buffer of at least 5 bytes for
unpacking 1 bytes at offset 4 (actual buffer size is 4)
…-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
This might have been my error all along. If Batched Read could account for
those errors and return N/A, None, or "" values there, that would be
amazing.
Even if not, it should definitely have a more descriptive error than a
buffer error.
Thanks again, and let me know if I can get you any more information on this!
On Mon, Dec 16, 2024 at 6:18 PM dmroeder ***@***.***> wrote:
@ammonwk <https://github.com/ammonwk>, are you able to run the lates
changes on the bugfix branch?
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|
Thanks for testing. How many bytes are the larger data types? |
|
I downloaded the branch |
|
I believe both issues are resolved in the branch. @ammonwk are you able to try it? |
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Type of issue
Description of issue
I get an exception reading 583 tags in batch
This error occurs with latest 1.0.5 version. Going back to my previous version 0.8.13, it works perfectly well.
Stacktrace
groot-svc | Exception reading 192.168.22.10: unpack_from requires a buffer of at least 49 bytes for unpacking 1 bytes at offset 48 (actual buffer size is 24)
groot-svc | File "/opt/everest/dev-ts-groot/groot_lib.py", line 194, in plc_read
groot-svc | results = comm.Read(batch)
groot-svc | File "/usr/local/lib/python3.10/site-packages/pylogix/eip.py", line 126, in Read
groot-svc | return self._batch_read(tag)
groot-svc | File "/usr/local/lib/python3.10/site-packages/pylogix/eip.py", line 376, in _batch_read
groot-svc | self._get_unknown_types(tags)
groot-svc | File "/usr/local/lib/python3.10/site-packages/pylogix/eip.py", line 1392, in _get_unknown_types
groot-svc | self._multi_read(unk_tags)
groot-svc | File "/usr/local/lib/python3.10/site-packages/pylogix/eip.py", line 428, in _multi_read
groot-svc | status, ret_data = self.conn.send(request)
groot-svc | File "/usr/local/lib/python3.10/site-packages/pylogix/lgx_comm.py", line 69, in send
groot-svc | return self._get_bytes(eip_header, connected)
groot-svc | File "/usr/local/lib/python3.10/site-packages/pylogix/lgx_comm.py", line 177, in _get_bytes
groot-svc | status = unpack_from('<B', ret_data, 48)[0]
Versions
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