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fix: Align all 0x34 and 0x36 framing bytes #848

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fix: Align all 0x34 and 0x36 framing bytes #848

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7 changes: 4 additions & 3 deletions s7commplus/async_client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@
_set_s7_groups,
)
from .protocol import (
FLAGS_34_FUNCTION_CODES,
READ_FUNCTION_CODES,
S7COMMPLUS_LOCAL_TSAP,
S7COMMPLUS_REMOTE_TSAP,
Expand Down Expand Up @@ -737,8 +738,8 @@ async def _send_request(
0x0000,
seq_num,
self._session_id,
# Transport flags: 0x34 for GetMultiVariables and Explore, 0x36 otherwise.
0x34 if function_code in (FunctionCode.GET_MULTI_VARIABLES, FunctionCode.EXPLORE) else 0x36,
# Transport flags: 0x34 for the function codes the reference sends with 0x34.
0x34 if function_code in FLAGS_34_FUNCTION_CODES else 0x36,
)

integrity_id_bytes = b""
Expand Down Expand Up @@ -992,7 +993,7 @@ async def _delete_session(self) -> None:
0x0000,
seq_num,
self._session_id,
0x36,
0x34,
)
request += struct.pack(">I", 0)

Expand Down
9 changes: 4 additions & 5 deletions s7commplus/connection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,7 @@

from .codec import decode_header, encode_header, encode_object_qualifier, parse_create_object_attributes
from .protocol import (
FLAGS_34_FUNCTION_CODES,
READ_FUNCTION_CODES,
S7COMMPLUS_LOCAL_TSAP,
S7COMMPLUS_REMOTE_TSAP,
Expand Down Expand Up @@ -716,10 +717,8 @@ def send_request(self, function_code: int, payload: bytes = b"", integrity_tail:
seq_num,
self._session_id,
# Transport flags: 0x34 after SessionKey auth (matches TIA Portal),
# also for GetMultiVariables and Explore; 0x36 for other V1/TLS requests.
0x34
if self._session_key is not None or function_code in (FunctionCode.GET_MULTI_VARIABLES, FunctionCode.EXPLORE)
else 0x36,
# and for the function codes the reference sends with 0x34.
0x34 if self._session_key is not None or function_code in FLAGS_34_FUNCTION_CODES else 0x36,
)

integrity_id_bytes = b""
Expand Down Expand Up @@ -1470,7 +1469,7 @@ def _delete_session(self) -> None:
0x0000,
seq_num,
self._session_id,
0x36,
0x34,
)
request += struct.pack(">I", 0)

Expand Down
20 changes: 20 additions & 0 deletions s7commplus/protocol.py
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Original file line number Diff line number Diff line change
Expand Up @@ -226,6 +226,26 @@ class Ids(IntEnum):
}
)

# Function codes whose requests carry transport flags 0x34. The reference sets
# this per request class rather than by read/write, so it is a different split
# than READ_FUNCTION_CODES: the writes SetVariable, SetMultiVariables and
# DeleteObject use 0x34 too. Only CreateObject (0x36) and InitSSL (0x30) differ,
# and a session-setup CreateObject sent with 0x34 makes the PLC reset the
# connection. Subscription and alarm CreateObjects are the documented exception:
# the reference overrides those to 0x34.
#
# Reference: TransportFlags in thomas-v2/S7CommPlusDriver/Core/*Request.cs
FLAGS_34_FUNCTION_CODES: frozenset[int] = frozenset(
{
FunctionCode.DELETE_OBJECT,
FunctionCode.EXPLORE,
FunctionCode.GET_MULTI_VARIABLES,
FunctionCode.GET_VAR_SUBSTREAMED,
FunctionCode.SET_MULTI_VARIABLES,
FunctionCode.SET_VARIABLE,
}
)


class AccessLevel(IntEnum):
"""Protection levels reported by `Ids.EFFECTIVE_PROTECTION_LEVEL`.
Expand Down
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