ROLLOUT 6 · pymodbus-dev/pymodbus
pymodbus-dev__pymodbus-1923
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Test failures/errors recorded in JUnit XML (failures=1, errors=0)
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System instructions 4,822 characters
You are a principal Python software engineer resolving a repository issue in `/workspace`. Your sole objective is to produce a minimal, root-cause source patch that passes every hidden fail-to-pass and pass-to-pass regression test on the first grading run. ## Critical Environment & Grader Rules 1. **Air-Gapped Sandbox & Available CLI Tools**: No network access. Never run `pip`, `uv`, `conda`, or `git fetch`. Note: `rg` (`ripgrep`) is NOT installed in the container — always use `grep -rn --include="*.py"` for fast exact searches so you never waste a tool call on `command not found`. 2. **Protected Grading Paths**: Before running official verification, the grading harness **strips and reverts all changes** to `tests/`, `test/`, `testing/`, `test_*.py`, `*_test.py`, `conftest.py`, `pyproject.toml`, `setup.cfg`, `pytest.ini`, and `tox.ini`. Every part of your fix MUST reside in non-test production source files. 3. **Untracked File Trap (`git add -N .`)**: `submit_patch` stages ALL untracked files inside `/workspace`! Never leave reproduction or scratch files inside `/workspace` — run reproductions inline via `python3 - <<'PY'` or inside `/tmp/repro.py` in a single `run_command`. 4. **Stdout Truncation Rule**: `run_command` truncates stdout after the first 5,000 characters from the TOP. Always run pytest quietly with short tracebacks: `pytest path/to/test_file.py -k pattern -q --tb=short --no-header` If a test file is large, redirect output to `/tmp/pytest.log` and inspect `tail -n 80 /tmp/pytest.log` so failure tracebacks at the bottom are never cut off. 5. **Strict Pacing Discipline**: `get_status` and `submit_patch` are free and do NOT count toward `max_tool_calls`. Target **16-22 counted tool calls total**, and **begin your first `edit_file` change no later than tool call 15**. Reserve at least 4 calls for verification, `git status --short && git diff`, and submission. ## Execution Protocol ### Phase 1 — Pinpoint Code & Tests Immediately (1-2 tool calls) - The user message already contains `Workspace Layout` — do NOT waste a turn running `ls` on top-level directories. - Run a single compound `run_command` with `grep -rn --include="*.py"` to locate: (a) the exact symbols, error strings, or functions from the problem description, (b) **all parallel or sibling implementations** (for example sync + async variants, `Client` + `AsyncClient`, serializer + deserializer, multiple backends/dialects, base + subclass methods, `__init__.py` / `__all__` exports), and (c) the closest existing unit test files under `tests/`. ### Phase 2 — Deep Read & Spec Anchor (2-5 tool calls) - Use `read_file` with generous `start_line` and `end_line` windows (180-300 lines per call so you read whole modules in fewer calls) on the target function/class, callers, type annotations, and neighboring tests. - Before editing, verify every explicit and implicit requirement from the issue: exact parameter names, defaults, boundary/domain edge cases, exception types/messages, `None` vs empty collection vs falsy (`0`, `False`, `""`) semantics, mutability/copying, and return types. ### Phase 3 — Reproduce Bug in One Call (1 tool call) - Run ONE concise command (`python3 - <<'PY' ... PY` or targeted `pytest ... -q --tb=short --no-header`) via `run_command` to observe the exact pre-fix failure. Do NOT spend multiple tool calls writing separate reproduction scripts. ### Phase 4 — Surgical Implementation Across All Parallel Paths (1-4 tool calls) - Begin editing by tool call 15! Use `edit_file` with 4-6 lines of exact surrounding context copied from `read_file`. - Update ALL parallel codepaths (sync/async, multiple classes/dialects, type hints) consistently so partial fixes do not fail sibling tests. - **2-Strike Edit Rule**: If `edit_file` fails twice on the same block due to whitespace or escaping, do not retry `edit_file` a third time — apply an atomic Python transformation via `run_command` and immediately verify `python3 -m py_compile path/to/file.py`. ### Phase 5 — Edge-Case Verification, Diff Hygiene & Clean Exit (2-4 tool calls) - Run a single compound `run_command` testing both your reproduction + boundary edge cases (`None`, empty input, leading/trailing delimiters, subdomain/prefix boundaries, subclass/async parity) AND the relevant existing `pytest` module(s) with `-q --tb=short --no-header`. - Run `git status --short && git diff` via `run_command`. Confirm: - ZERO untracked (`??`) files in `/workspace` (`rm -f` any untracked workspace files immediately), - ZERO modifications to `tests/` or protected config files (`git checkout -- tests/` if touched), - Minimal, clean diff with valid imports and indentation. - Call `submit_patch` once verification passes, then respond with a brief 2-sentence plain-text summary and make NO further tool calls.
Task prompt 11,117 characters
You are evaluating a software engineering task for repository pymodbus-dev/pymodbus.
Problem Statement:
Pymodbus doesn't correctly handle Reassembled TCP segments
### Versions
- Python: Python: 3.11.4
- OS: Ubuntu 20.04
- Pymodbus: pymodbus-3.7.0.dev0 (git commit 81df5b1cde349dddd32ac3c1fd97ec4b475c2512) as well as 3.5.4
- Modbus Hardware (if used): SMA STP 6000TL-20 (version 02.51.02.R)
### Pymodbus Specific
- Client: tcp - async
### Description
When trying to read registers from the SMA STP 6000TL Inverter, the Modbus Response is split over 2 frames where the second frame only contains the last required byte. pymodbus doesn't seem to reassemble the modbus frames and instead tries parsing the first frame as a modbus response which it discards because it doesn't pass the Frame check. It then tries reading the second frame (consisting of only one byte) as a response and throws an exception because it can't decode it.
pymodbus should probably check the length of the tcp packet and only run the frame check once the complete packet has arrived. I've attached the client code, pymodbus logs and a wireshark capture of the modbus traffic.
### Code and Logs
[20240104_tcp_reassembly.pcapng.gz](https://github.com/pymodbus-dev/pymodbus/files/13828939/20240104_tcp_reassembly.pcapng.gz)
```python
import asyncio
import pymodbus
from pymodbus.client import AsyncModbusTcpClient
from pymodbus.constants import Endian
from pymodbus.exceptions import ModbusException
from pymodbus.payload import BinaryPayloadDecoder
from pymodbus.pdu import ExceptionResponse
pymodbus.pymodbus_apply_logging_config("DEBUG")
async def main():
async with AsyncModbusTcpClient(
host="127.0.0.1", port=5502, reconnect_delay=0
) as mbus:
response = await mbus.read_holding_registers(42109, 4, slave=1)
decoder = BinaryPayloadDecoder.fromRegisters(
response.registers, byteorder=Endian.BIG, wordorder=Endian.BIG
)
_serial = decoder.decode_32bit_uint()
_susy_id = decoder.decode_16bit_uint()
unit_id = decoder.decode_16bit_uint()
if __name__ == "__main__":
asyncio.run(main())
```
Logs:
```
2024-01-04 11:16:16,385 DEBUG logging:103 Connecting to 127.0.0.1:5502.
2024-01-04 11:16:16,385 DEBUG logging:103 Connecting comm
2024-01-04 11:16:16,385 DEBUG logging:103 Connected to comm
2024-01-04 11:16:16,385 DEBUG logging:103 callback_connected called
2024-01-04 11:16:16,385 DEBUG logging:103 send: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x3 0xa4 0x7d 0x0 0x4
2024-01-04 11:16:16,385 DEBUG logging:103 Adding transaction 1
2024-01-04 11:16:16,635 DEBUG logging:103 recv: 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0 old_data: addr=None
2024-01-04 11:16:16,635 DEBUG logging:103 Processing: 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0
2024-01-04 11:16:16,635 DEBUG logging:103 Frame check failed, ignoring!!
2024-01-04 11:16:16,635 DEBUG logging:103 Resetting frame - Current Frame in buffer - 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0
2024-01-04 11:16:16,719 DEBUG logging:103 recv: 0x3 old_data: addr=None
2024-01-04 11:16:16,719 DEBUG logging:103 Processing: 0x3
2024-01-04 11:16:16,719 DEBUG logging:103 Factory Response[ReadHoldingRegistersResponse': 3]
2024-01-04 11:16:16,719 ERROR logging:115 General exception: index out of range
2024-01-04 11:16:16,719 DEBUG logging:103 Resetting frame - Current Frame in buffer - 0x3
Fatal error: protocol.data_received() call failed.
protocol: <pymodbus.client.tcp.AsyncModbusTcpClient object at 0x7fa70e325f70>
transport: <_SelectorSocketTransport fd=6 read=polling write=<idle, bufsize=0>>
Traceback (most recent call last):
File "/usr/lib/python3.8/asyncio/selector_events.py", line 862, in _read_ready__data_received
self._protocol.data_received(data)
File "/home/simon/tools/pymodbus/pymodbus/transport/transport.py", line 318, in data_received
self.datagram_received(data, None)
File "/home/simon/tools/pymodbus/pymodbus/transport/transport.py", line 352, in datagram_received
cut = self.callback_data(self.recv_buffer, addr=addr)
File "/home/simon/tools/pymodbus/pymodbus/client/base.py", line 186, in callback_data
self.framer.processIncomingPacket(data, self._handle_response, slave=0)
File "/home/simon/tools/pymodbus/pymodbus/framer/base.py", line 139, in processIncomingPacket
self.frameProcessIncomingPacket(single, callback, slave, **kwargs)
File "/home/simon/tools/pymodbus/pymodbus/framer/socket_framer.py", line 136, in frameProcessIncomingPacket
self._process(callback, tid, error=True)
File "/home/simon/tools/pymodbus/pymodbus/framer/socket_framer.py", line 154, in _process
raise ModbusIOException("Unable to decode request")
pymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] Unable to decode request
2024-01-04 11:16:16,721 DEBUG logging:103 Connection lost comm due to Modbus Error: [Input/Output] Unable to decode request
2024-01-04 11:16:16,721 DEBUG logging:103 Getting transaction 1
Traceback (most recent call last):
File "bug_reproducer.py", line 27, in <module>
asyncio.run(main())
File "/usr/lib/python3.8/asyncio/runners.py", line 44, in run
return loop.run_until_complete(main)
File "/usr/lib/python3.8/asyncio/base_events.py", line 616, in run_until_complete
return future.result()
File "bug_reproducer.py", line 17, in main
response = await mbus.read_holding_registers(42109, 4, slave=1)
File "/home/simon/tools/pymodbus/pymodbus/client/base.py", line 167, in async_execute
resp = await asyncio.wait_for(
File "/usr/lib/python3.8/asyncio/tasks.py", line 494, in wait_for
return fut.result()
pymodbus.exceptions.ConnectionException: Modbus Error: [Connection] Connection lost during request
```
## Task Budget (Session terminates when any budget is exhausted)
- Time allowance: 7.5 minutes
- Tool calls allowance: 30 calls
- Max loop iterations: 40 turns
## Execution Environment Rules
- Single command timeout: 90 seconds (commands exceeding this fail without ending the session)
- Command output limit: 5000 characters
- File view limit: 150 lines per read_file call
- File character limit: 10000 characters per read_file call
- Environment is offline (no network/PyPI access). All repository and test dependencies are ALREADY pre-installed. Do NOT attempt to run pip install or download packages.
## Instructions:
0. All source code is under `/workspace`. Do NOT search outside `/workspace` (e.g. `/usr/`, `/wheels/`, system site-packages). If imports fail, the issue is in the source code under `/workspace`, not in missing system packages.
1. Analyze the problem statement and any provided hints carefully to identify all requested script paths, CLI subcommands, or Python modules.
2. Inspect existing codebase conventions and test files before making edits.
3. Verify your implementation using targeted tests or inline assertions before submitting.
4. Call submit_patch only after your implementation is complete and verified.
5. As your final action, you must return a text-only response reporting your completion to terminate the session.
## Workspace Layout
The repository is located at `/workspace`. Here is the directory tree (up to 3 levels):
```
./API_changes.rst
./AUTHORS.rst
./CHANGELOG.rst
./CONTRIBUTING.rst
./LICENSE
./MAKE_RELEASE.rst
./MANIFEST.in
./README.rst
./check_ci.sh
./doc
./doc/Makefile
./doc/build_html
./doc/conf.py
./doc/index.rst
./doc/source
./doc/source/REPL.rst
./doc/source/_static
./doc/source/api_changes.rst
./doc/source/authors.rst
./doc/source/changelog.rst
./doc/source/client.rst
./doc/source/examples.rst
./doc/source/internals.rst
./doc/source/library
./doc/source/readme.rst
./doc/source/server.rst
./doc/source/simulator.rst
./examples
./githooks
./githooks/pre-commit
./pymodbus
./pymodbus/__init__.py
./pymodbus/bit_read_message.py
./pymodbus/bit_write_message.py
./pymodbus/client
./pymodbus/client/__init__.py
./pymodbus/client/base.py
./pymodbus/client/mixin.py
./pymodbus/client/serial.py
./pymodbus/client/tcp.py
./pymodbus/client/tls.py
./pymodbus/client/udp.py
./pymodbus/constants.py
./pymodbus/datastore
./pymodbus/datastore/__init__.py
./pymodbus/datastore/context.py
./pymodbus/datastore/remote.py
./pymodbus/datastore/simulator.py
./pymodbus/datastore/store.py
./pymodbus/device.py
./pymodbus/diag_message.py
./pymodbus/events.py
./pymodbus/exceptions.py
./pymodbus/factory.py
./pymodbus/file_message.py
./pymodbus/framer
./pymodbus/framer/__init__.py
./pymodbus/framer/ascii_framer.py
./pymodbus/framer/base.py
./pymodbus/framer/binary_framer.py
./pymodbus/framer/rtu_framer.py
./pymodbus/framer/socket_framer.py
./pymodbus/framer/tls_framer.py
./pymodbus/logging.py
./pymodbus/mei_message.py
./pymodbus/other_message.py
./pymodbus/payload.py
./pymodbus/pdu.py
./pymodbus/py.typed
./pymodbus/register_read_message.py
./pymodbus/register_write_message.py
./pymodbus/repl
./pymodbus/repl/README.rst
./pymodbus/repl/__init__.py
./pymodbus/repl/client
./pymodbus/repl/server
./pymodbus/server
./pymodbus/server/__init__.py
./pymodbus/server/async_io.py
./pymodbus/server/reactive
./pymodbus/server/simulator
./pymodbus/transaction.py
./pymodbus/transport
./pymodbus/transport/__init__.py
./pymodbus/transport/transport.py
./pymodbus/transport/transport_serial.py
./pymodbus/utilities.py
./pyproject.toml
./test
./test/__init__.py
./test/conftest.py
./test/sub_client
./test/sub_client/test_client.py
./test/sub_client/test_client_faulty_response.py
./test/sub_client/test_client_sync.py
./test/sub_client/test_repl_client.py
./test/sub_examples
./test/sub_examples/__init__.py
./test/sub_examples/conftest.py
./test/sub_examples/test_client_server_async.py
./test/sub_examples/test_client_server_sync.py
./test/sub_examples/test_examples.py
./test/sub_examples/test_helper.py
./test/sub_messages
./test/sub_messages/test_all_messages.py
./test/sub_messages/test_bit_read_messages.py
./test/sub_messages/test_bit_write_messages.py
./test/sub_messages/test_diag_messages.py
./test/sub_messages/test_mei_messages.py
./test/sub_messages/test_other_messages.py
./test/sub_messages/test_register_read_messages.py
./test/sub_messages/test_register_write_messages.py
./test/sub_server
./test/sub_server/test_server_asyncio.py
./test/sub_server/test_server_context.py
./test/sub_server/test_server_multidrop.py
./test/sub_server/test_simulator.py
./test/sub_transport
./test/sub_transport/__init__.py
./test/sub_transport/conftest.py
./test/sub_transport/test_basic.py
./test/sub_transport/test_comm.py
./test/sub_transport/test_nullmodem.py
./test/sub_transport/test_protocol.py
./test/sub_transport/test_reconnect.py
./test/test_device.py
./test/test_events.py
./test/test_exceptions.py
./test/test_factory.py
./test/test_file_message.py
./test/test_framers.py
./test/test_logging.py
./test/test_payload.py
./test/test_pdu.py
./test/test_remote_datastore.py
./test/test_sparse_datastore.py
./test/test_transaction.py
./test/test_utilities.py
```
Turn 1at 45 s319 tokens out6,231 prompt tokens
The user is reporting an issue where `pymodbus` fails to handle reassembled TCP segments. Specifically, when a Modbus response is split over two TCP frames, the first frame is processed separately and fails the frame check, and the second frame is also processed separately and fails to decode. This suggests that the Modbus TCP framer should buffer data until a full frame (as indicated by the Modbus TCP header length) has arrived. From the traceback: - `pymodbus/transport/transport.py` calls `datagram_received` - `pymodbus/client/base.py` calls `self.framer.processIncomingPacket` - `pymodbus/framer/base.py` calls `self.frameProcessIncomingPacket` - `pymodbus/framer/socket_framer.py` is where `frameProcessIncomingPacket` is implemented. The issue specifically mentions `AsyncModbusTcpClient`, so it's likely related to `SocketFramer` (since TCP uses sockets). I need to look at `pymodbus/framer/socket_framer.py` to see how it handles incoming packets. Let's start by exploring the code and reproducing the issue.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" \"processIncomingPacket\" pymodbus/framer/socket_framer.py pymodbus/framer/base.py"
}Result of run_command 159 characters
{
"status": "ok",
"stdout": "pymodbus/framer/base.py:115: def processIncomingPacket(self, data, callback, slave, **kwargs):\n",
"stderr": "",
"exit_code": 0
}Generated tokens 319 tokens · stopped: STOP
<|channel>thought
The user is reporting an issue where `pymodbus` fails to handle reassembled TCP segments.
Specifically, when a Modbus response is split over two TCP frames, the first frame is processed separately and fails the frame check, and the second frame is also processed separately and fails to decode.
This suggests that the Modbus TCP framer should buffer data until a full frame (as indicated by the Modbus TCP header length) has arrived.
From the traceback:
- `pymodbus/transport/transport.py` calls `datagram_received`
- `pymodbus/client/base.py` calls `self.framer.processIncomingPacket`
- `pymodbus/framer/base.py` calls `self.frameProcessIncomingPacket`
- `pymodbus/framer/socket_framer.py` is where `frameProcessIncomingPacket` is implemented.
The issue specifically mentions `AsyncModbusTcpClient`, so it's likely related to `SocketFramer` (since TCP uses sockets).
I need to look at `pymodbus/framer/socket_framer.py` to see how it handles incoming packets.
Let's start by exploring the code and reproducing the issue.<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" "processIncomingPacket" pymodbus/framer/socket_framer.py pymodbus/framer/base.py<|"|>}<tool_call|><|tool_response>
Turn 2at 58 s213 tokens out6,622 prompt tokens
Wait, `grep` didn't show `processIncomingPacket` in `socket_framer.py` but the traceback said: `File "/home/simon/tools/pymodbus/pymodbus/framer/socket_framer.py", line 136, in frameProcessIncomingPacket` and `File "/home/simon/tools/pymodbus/pymodbus/framer/base.py", line 139, in processIncomingPacket` `self.frameProcessIncomingPacket(single, callback, slave, **kwargs)` Ah, `socket_framer.py` likely implements `frameProcessIncomingPacket`, not `processIncomingPacket`. Let me check `socket_framer.py` for `frameProcessIncomingPacket`.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" \"frameProcessIncomingPacket\" pymodbus/framer/socket_framer.py"
}Result of run_command 152 characters
{
"status": "ok",
"stdout": "119: def frameProcessIncomingPacket(self, single, callback, slave, tid=None, **kwargs):\n",
"stderr": "",
"exit_code": 0
}Generated tokens 213 tokens · stopped: STOP
Wait, `grep` didn't show `processIncomingPacket` in `socket_framer.py` but the traceback said:
`File "/home/simon/tools/pymodbus/pymodbus/framer/socket_framer.py", line 136, in frameProcessIncomingPacket`
and
`File "/home/simon/tools/pymodbus/pymodbus/framer/base.py", line 139, in processIncomingPacket`
`self.frameProcessIncomingPacket(single, callback, slave, **kwargs)`
Ah, `socket_framer.py` likely implements `frameProcessIncomingPacket`, not `processIncomingPacket`. Let me check `socket_framer.py` for `frameProcessIncomingPacket`.
<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" "frameProcessIncomingPacket" pymodbus/framer/socket_framer.py<|"|>}<tool_call|><|tool_response>
Turn 3at 62 s79 tokens out6,900 prompt tokens
Okay, so `SocketFramer.frameProcessIncomingPacket` is the place. Let's read `pymodbus/framer/socket_framer.py` and `pymodbus/framer/base.py`.
TOOL CALL · read_file
{
"filepath": "pymodbus/framer/socket_framer.py"
}Result of read_file 5,838 characters
{
"status": "ok",
"filepath": "pymodbus/framer/socket_framer.py",
"content": "\"\"\"Socket framer.\"\"\"\n# pylint: disable=missing-type-doc\nimport struct\n\nfrom pymodbus.exceptions import (\n InvalidMessageReceivedException,\n ModbusIOException,\n)\nfrom pymodbus.framer.base import SOCKET_FRAME_HEADER, ModbusFramer\nfrom pymodbus.logging import Log\n\n\n# --------------------------------------------------------------------------- #\n# Modbus TCP Message\n# --------------------------------------------------------------------------- #\n\n\nclass ModbusSocketFramer(ModbusFramer):\n \"\"\"Modbus Socket Frame controller.\n\n Before each modbus TCP message is an MBAP header which is used as a\n message frame. It allows us to easily separate messages as follows::\n\n [ MBAP Header ] [ Function Code] [ Data ] \\\n [ tid ][ pid ][ length ][ uid ]\n 2b 2b 2b 1b 1b Nb\n\n while len(message) > 0:\n tid, pid, length`, uid = struct.unpack(\">HHHB\", message)\n request = message[0:7 + length - 1`]\n message = [7 + length - 1:]\n\n * length = uid + function code + data\n * The -1 is to account for the uid byte\n \"\"\"\n\n method = \"socket\"\n\n def __init__(self, decoder, client=None):\n \"\"\"Initialize a new instance of the framer.\n\n :param decoder: The decoder factory implementation to use\n \"\"\"\n super().__init__(decoder, client)\n self._hsize = 0x07\n\n # ----------------------------------------------------------------------- #\n # Private Helper Functions\n # ----------------------------------------------------------------------- #\n def checkFrame(self):\n \"\"\"Check and decode the next frame.\n\n Return true if we were successful.\n \"\"\"\n if self.isFrameReady():\n (\n self._header[\"tid\"],\n self._header[\"pid\"],\n self._header[\"len\"],\n self._header[\"uid\"],\n ) = struct.unpack(\">HHHB\", self._buffer[0 : self._hsize])\n\n # someone sent us an error? ignore it\n if self._header[\"len\"] < 2:\n self.advanceFrame()\n # we have at least a complete message, continue\n elif len(self._buffer) - self._hsize + 1 >= self._header[\"len\"]:\n return True\n # we don't have enough of a message yet, wait\n return False\n\n def advanceFrame(self):\n \"\"\"Skip over the current framed message.\n\n This allows us to skip over the current message after we have processed\n it or determined that it contains an error. It also has to reset the\n current frame header handle\n \"\"\"\n length = self._hsize + self._header[\"len\"] - 1\n self._buffer = self._buffer[length:]\n self._header = {\"tid\": 0, \"pid\": 0, \"len\": 0, \"uid\": 0}\n\n def isFrameReady(self):\n \"\"\"Check if we should continue decode logic.\n\n This is meant to be used in a while loop in the decoding phase to let\n the decoder factory know that there is still data in the buffer.\n\n :returns: True if ready, False otherwise\n \"\"\"\n return len(self._buffer) > self._hsize\n\n def getFrame(self):\n \"\"\"Return the next frame from the buffered data.\n\n :returns: The next full frame buffer\n \"\"\"\n length = self._hsize + self._header[\"len\"] - 1\n return self._buffer[self._hsize : length]\n\n # ----------------------------------------------------------------------- #\n # Public Member Functions\n # ----------------------------------------------------------------------- #\n def decode_data(self, data):\n \"\"\"Decode data.\"\"\"\n if len(data) > self._hsize:\n tid, pid, length, uid, fcode = struct.unpack(\n SOCKET_FRAME_HEADER, data[0 : self._hsize + 1]\n )\n return {\n \"tid\": tid,\n \"pid\": pid,\n \"length\": length,\n \"slave\": uid,\n \"fcode\": fcode,\n }\n return {}\n\n def frameProcessIncomingPacket(self, single, callback, slave, tid=None, **kwargs):\n \"\"\"Process new packet pattern.\n\n This takes in a new request packet, adds it to the current\n packet stream, and performs framing on it. That is, checks\n for complete messages, and once found, will process all that\n exist. This handles the case when we read N + 1 or 1 // N\n messages at a time instead of 1.\n\n The processed and decoded messages are pushed to the callback\n function to process and send.\n \"\"\"\n while True:\n if not self.isFrameReady():\n if len(self._buffer):\n # Possible error ???\n if self._header[\"len\"] < 2:\n self._process(callback, tid, error=True)\n break\n if not self.checkFrame():\n Log.debug(\"Frame check failed, ignoring!!\")\n self.resetFrame()\n continue\n if not self._validate_slave_id(slave, single):\n header_txt = self._header[\"uid\"]\n Log.debug(\"Not a valid slave id - {}, ignoring!!\", header_txt)\n self.resetFrame()\n continue\n self._process(callback, tid)\n\n def _process(self, callback, tid, error=False):\n \"\"\"Process incoming packets irrespective error condition.\"\"\"",
"start_line": 1,
"end_line": 150,
"total_lines": 182,
"is_truncated": true
}Generated tokens 79 tokens · stopped: STOP
Okay, so `SocketFramer.frameProcessIncomingPacket` is the place.
Let's read `pymodbus/framer/socket_framer.py` and `pymodbus/framer/base.py`.
<channel|><|tool_call>call:read_file{filepath:<|"|>pymodbus/framer/socket_framer.py<|"|>}<tool_call|><|tool_response>
Turn 4at 67 s70 tokens out8,513 prompt tokens
I need to read the rest of `pymodbus/framer/socket_framer.py` to see `_process` and `resetFrame`.
TOOL CALL · read_file
{
"filepath": "pymodbus/framer/socket_framer.py",
"start_line": 151
}Result of read_file 1,215 characters
{
"status": "ok",
"filepath": "pymodbus/framer/socket_framer.py",
"content": " data = self._buffer if error else self.getFrame()\n if (result := self.decoder.decode(data)) is None:\n self.resetFrame()\n raise ModbusIOException(\"Unable to decode request\")\n if error and result.function_code < 0x80:\n raise InvalidMessageReceivedException(result)\n self.populateResult(result)\n self.advanceFrame()\n if tid and tid != result.transaction_id:\n self.resetFrame()\n else:\n callback(result) # defer or push to a thread?\n\n def buildPacket(self, message):\n \"\"\"Create a ready to send modbus packet.\n\n :param message: The populated request/response to send\n \"\"\"\n data = message.encode()\n packet = struct.pack(\n SOCKET_FRAME_HEADER,\n message.transaction_id,\n message.protocol_id,\n len(data) + 2,\n message.slave_id,\n message.function_code,\n )\n packet += data\n return packet\n\n\n# __END__",
"start_line": 151,
"end_line": 182,
"total_lines": 182,
"is_truncated": false
}Generated tokens 70 tokens · stopped: STOP
I need to read the rest of `pymodbus/framer/socket_framer.py` to see `_process` and `resetFrame`.
<channel|><|tool_call>call:read_file{filepath:<|"|>pymodbus/framer/socket_framer.py<|"|>,start_line:151}<tool_call|><|tool_response>
Turn 5at 72 s86 tokens out8,934 prompt tokens
Wait, I don't see `resetFrame()` implementation in `ModbusSocketFramer`. It must be in `ModbusFramer` in `pymodbus/framer/base.py`. Let's check `pymodbus/framer/base.py`.
TOOL CALL · read_file
{
"filepath": "pymodbus/framer/base.py"
}Result of read_file 4,882 characters
{
"status": "ok",
"filepath": "pymodbus/framer/base.py",
"content": "\"\"\"Framer start.\"\"\"\n# pylint: disable=missing-type-doc\nfrom __future__ import annotations\n\nfrom typing import Any\n\nfrom pymodbus.factory import ClientDecoder, ServerDecoder\nfrom pymodbus.logging import Log\n\n\n# Unit ID, Function Code\nBYTE_ORDER = \">\"\nFRAME_HEADER = \"BB\"\n\n# Transaction Id, Protocol ID, Length, Unit ID, Function Code\nSOCKET_FRAME_HEADER = BYTE_ORDER + \"HHH\" + FRAME_HEADER\n\n# Function Code\nTLS_FRAME_HEADER = BYTE_ORDER + \"B\"\n\n\nclass ModbusFramer:\n \"\"\"Base Framer class.\"\"\"\n\n name = \"\"\n\n def __init__(\n self,\n decoder: ClientDecoder | ServerDecoder,\n client=None,\n ) -> None:\n \"\"\"Initialize a new instance of the framer.\n\n :param decoder: The decoder implementation to use\n \"\"\"\n self.decoder = decoder\n self.client = client\n self._header: dict[str, Any] = {\n \"lrc\": \"0000\",\n \"len\": 0,\n \"uid\": 0x00,\n \"tid\": 0,\n \"pid\": 0,\n \"crc\": b\"\\x00\\x00\",\n }\n self._buffer = b\"\"\n\n def _validate_slave_id(self, slaves: list, single: bool) -> bool:\n \"\"\"Validate if the received data is valid for the client.\n\n :param slaves: list of slave id for which the transaction is valid\n :param single: Set to true to treat this as a single context\n :return:\n \"\"\"\n if single:\n return True\n if 0 in slaves or 0xFF in slaves:\n # Handle Modbus TCP slave identifier (0x00 0r 0xFF)\n # in asynchronous requests\n return True\n return self._header[\"uid\"] in slaves\n\n def sendPacket(self, message):\n \"\"\"Send packets on the bus.\n\n With 3.5char delay between frames\n :param message: Message to be sent over the bus\n :return:\n \"\"\"\n return self.client.send(message)\n\n def recvPacket(self, size):\n \"\"\"Receive packet from the bus.\n\n With specified len\n :param size: Number of bytes to read\n :return:\n \"\"\"\n return self.client.recv(size)\n\n def resetFrame(self):\n \"\"\"Reset the entire message frame.\n\n This allows us to skip ovver errors that may be in the stream.\n It is hard to know if we are simply out of sync or if there is\n an error in the stream as we have no way to check the start or\n end of the message (python just doesn't have the resolution to\n check for millisecond delays).\n \"\"\"\n Log.debug(\n \"Resetting frame - Current Frame in buffer - {}\", self._buffer, \":hex\"\n )\n self._buffer = b\"\"\n self._header = {\n \"lrc\": \"0000\",\n \"crc\": b\"\\x00\\x00\",\n \"len\": 0,\n \"uid\": 0x00,\n \"pid\": 0,\n \"tid\": 0,\n }\n\n def populateResult(self, result):\n \"\"\"Populate the modbus result header.\n\n The serial packets do not have any header information\n that is copied.\n\n :param result: The response packet\n \"\"\"\n result.slave_id = self._header.get(\"uid\", 0)\n result.transaction_id = self._header.get(\"tid\", 0)\n result.protocol_id = self._header.get(\"pid\", 0)\n\n def processIncomingPacket(self, data, callback, slave, **kwargs):\n \"\"\"Process new packet pattern.\n\n This takes in a new request packet, adds it to the current\n packet stream, and performs framing on it. That is, checks\n for complete messages, and once found, will process all that\n exist. This handles the case when we read N + 1 or 1 // N\n messages at a time instead of 1.\n\n The processed and decoded messages are pushed to the callback\n function to process and send.\n\n :param data: The new packet data\n :param callback: The function to send results to\n :param slave: Process if slave id matches, ignore otherwise (could be a\n list of slave ids (server) or single slave id(client/server))\n :param kwargs:\n :raises ModbusIOException:\n \"\"\"\n Log.debug(\"Processing: {}\", data, \":hex\")\n self._buffer += data\n if not isinstance(slave, (list, tuple)):\n slave = [slave]\n single = kwargs.pop(\"single\", False)\n self.frameProcessIncomingPacket(single, callback, slave, **kwargs)\n\n def frameProcessIncomingPacket(\n self, _single, _callback, _slave, _tid=None, **kwargs\n ):\n \"\"\"Process new packet pattern.\"\"\"",
"start_line": 1,
"end_line": 144,
"total_lines": 144,
"is_truncated": false
}Generated tokens 86 tokens · stopped: STOP
Wait, I don't see `resetFrame()` implementation in `ModbusSocketFramer`. It must be in `ModbusFramer` in `pymodbus/framer/base.py`.
Let's check `pymodbus/framer/base.py`.
<channel|><|tool_call>call:read_file{filepath:<|"|>pymodbus/framer/base.py<|"|>}<tool_call|><|tool_response>
Turn 6at 302 s3,688 tokens out10,429 prompt tokens
Now let's analyze `ModbusSocketFramer.frameProcessIncomingPacket`:
```python
def frameProcessIncomingPacket(self, single, callback, slave, tid=None, **kwargs):
"""Process new packet pattern.
This takes in a new request packet, adds it to the current
packet stream, and performs framing on it. That is, checks
for complete messages, and once found, will process all that
exist. This handles the case when we read N + 1 or 1 // N
messages at a time instead of 1.
The processed and decoded messages are pushed to the callback
function to process and send.
"""
while True:
if not self.isFrameReady():
if len(self._buffer):
# Possible error ???
if self._header["len"] < 2:
self._process(callback, tid, error=True)
break
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
if not self._validate_slave_id(slave, single):
header_txt = self._header["uid"]
Log.debug("Not a valid slave id - {}, ignoring!!", header_txt)
self.resetFrame()
continue
self._process(callback, tid)
```
And `isFrameReady`:
```python
def isFrameReady(self):
"""Check if we should continue decode logic.
This is meant to be used in a while loop in the decoding phase to let
the decoder factory know that there is still data in the buffer.
:returns: True if ready, False otherwise
"""
return len(self._buffer) > self._hsize
```
`self._hsize` is `0x07` (7 bytes), which is the size of the MBAP header (tid 2, pid 2, len 2, uid 1).
And `checkFrame`:
```python
def checkFrame(self):
"""Check and decode the next frame.
Return true if we were successful.
"""
if self.isFrameReady():
(
self._header["tid"],
self._header["pid"],
self._header["len"],
self._header["uid"],
) = struct.unpack(">HHHB", self._buffer[0 : self._hsize])
# someone sent us an error? ignore it
if self._header["len"] < 2:
self.advanceFrame()
# we have at least a complete message, continue
elif len(self._buffer) - self._hsize + 1 >= self._header["len"]:
return True
# we don't have enough of a message yet, wait
return False
```
Wait, I see the problem. If `checkFrame()` returns `False`, `frameProcessIncomingPacket` does this:
```python
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
```
`self.resetFrame()` clears `self._buffer`!
```python
def resetFrame(self):
# ...
self._buffer = b""
# ...
```
So if `checkFrame()` returns `False` (meaning the full frame hasn't arrived yet), it wipes the buffer and starts over. This is exactly what the problem description says: "pymodbus doesn't seem to reassemble the modbus frames and instead tries parsing the first frame as a modbus response which it discards because it doesn't pass the Frame check."
The fix should be that if `checkFrame()` returns `False`, it should simply `break` the loop and wait for more data, rather than calling `resetFrame()` and `continue`.
Let's verify this with a reproduction script.
I will create a mock server that sends a Modbus TCP response in two pieces.
MBAP Header:
TID: 1 (2 bytes) -> \x00\x01
PID: 0 (2 bytes) -> \x00\x00
Length: 6 (2 bytes) -> \x00\x06 (Length is UID + PDU)
UID: 1 (1 byte) -> \x01
PDU: Function code 3, Data length 8, Data (8 bytes) = 1 + 1 + 8 = 10 bytes? No, length is from UID.
Wait, let's look at the MBAP header format:
[ tid 2b ][ pid 2b ][ length 2b ][ uid 1b ]
Length is the number of bytes following the length field. So `length = uid + pdu_length`.
Example: UID (1 byte) + Function Code (1 byte) + Byte Count (1 byte) + Data (N bytes).
Total = 1 + 1 + 1 + N bytes.
In the user's logs:
`recv: 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`
TID: 0x0001
PID: 0x0000
Length: 0x000b (11 decimal)
UID: 0x01
PDU: 0x03 (Read Holding Registers), 0x08 (Byte count), 0x00 0xb5 0x12 0x2f 0x37 0x21 0x00 (Wait, 0x00 0xb5 is 2 bytes, 0x12 0x2f is 2 bytes, 0x37 0x21 is 2 bytes, 0x00 is 1 byte. That's 7 bytes).
Total PDU = 1 (FC) + 1 (Byte count) + 7 (Data) = 9 bytes.
UID (1) + PDU (9) = 10 bytes.
Wait, the log says length is 0x0b (11).
Maybe the PDU is 10 bytes?
Let's count the bytes in `0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`.
`0x1` (UID)
`0x3` (FC)
`0x8` (Byte count)
`0x0`
`0xb5`
`0x12`
`0x2f`
`0x37`
`0x21`
`0x0`
Total: 10 bytes.
Wait, the log says `recv: ... 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 ...`
TID: 0, 1
PID: 0, 0
Length: 0, 11 (0x0b)
UID: 1
PDU: 3, 8, 0, 0xb5, 0x12, 0x2f, 0x37, 0x21, 0 (Wait, 0x0 is the 9th byte of PDU)
Wait, 11 bytes after Length field = UID(1) + PDU(10).
UID=1, PDU = 3, 8, 0, 0xb5, 0x12, 0x2f, 0x37, 0x21, 0, ...?
The log says `0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`
That's 16 bytes.
Header: 0, 1, 0, 0, 0, 11 (6 bytes)
Remaining: 1, 3, 8, 0, 0xb5, 0x12, 0x2f, 0x37, 0x21, 0 (10 bytes)
Total: 16 bytes.
So Length = 10. But the log says `0x0 0xb` (11).
Wait, `0 1 0 0 0 b`. `0x0b` is 11.
If length is 11, it expects 11 bytes after length.
`1 3 8 0 0xb5 0x12 0x2f 0x37 0x21 0` - that's 10 bytes.
So the 11th byte was sent in the next frame!
`recv: 0x3`
Exactly what the user said: "the second frame only contains the last required byte".
So we have:
Frame 1: MBAP header (Length=11), UID(1), PDU(9 bytes: FC=3, Len=8, Data=7 bytes). Total 15 bytes.
Frame 2: 1 byte (the 8th byte of data).
When Frame 1 arrives:
`isFrameReady()` returns `True` (len=15 > 7).
`checkFrame()`:
`self._header['len']` becomes 11.
`len(self._buffer) - self._hsize + 1` = `15 - 7 + 1` = 9.
Is `9 >= 11`? No.
So `checkFrame()` returns `False`.
Then `frameProcessIncomingPacket` calls `resetFrame()` and wipes the buffer.
Then Frame 2 arrives:
`isFrameReady()`: buffer now contains only `0x03` (1 byte). `1 > 7` is `False`.
Loop breaks.
Wait, if Frame 2 arrives and `isFrameReady` is False, it doesn't call `_process(callback, tid, error=True)` unless `self._header['len'] < 2`.
But `self._header` was reset!
Actually, in the logs:
`2024-01-04 11:16:16,635 DEBUG logging:103 Frame check failed, ignoring!!`
`2024-01-04 11:16:16,635 DEBUG logging:103 Resetting frame - Current Frame in buffer - 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`
`2024-01-04 11:16:16,719 DEBUG logging:103 recv: 0x3 old_data: addr=None`
`2024-01-04 11:16:16,719 DEBUG logging:103 Processing: 0x3`
`2024-01-04 11:16:16,719 DEBUG logging:103 Factory Response[ReadHoldingRegistersResponse': 3]`
`2024-01-04 11:16:16,719 ERROR logging:115 General exception: index out of range`
Wait, why did it try to parse `0x3` as a response?
In `processIncomingPacket`:
```python
def processIncomingPacket(self, data, callback, slave, **kwargs):
Log.debug("Processing: {}", data, ":hex")
self._buffer += data
if not isinstance(slave, (list, tuple)):
slave = [slave]
single = kwargs.pop("single", False)
self.frameProcessIncomingPacket(single, callback, slave, **kwargs)
```
When `0x03` arrives, `self._buffer` becomes `b'\x03'`.
Then `frameProcessIncomingPacket` is called.
`isFrameReady()` returns `False` (len=1 < 7).
```python
if not self.isFrameReady():
if len(self._buffer):
# Possible error ???
if self._header["len"] < 2:
self._process(callback, tid, error=True)
break
```
After `resetFrame()`, `self._header["len"]` is `0`.
So `0 < 2` is `True`.
It calls `self._process(callback, tid, error=True)`.
`_process` with `error=True` uses `data = self._buffer`.
So `data = b'\x03'`.
Then `self.decoder.decode(b'\x03')` is called.
Depending on the decoder, this might return something (like a response with function code 3) or throw an exception.
In the log, it seems it returned a `ReadHoldingRegistersResponse` object, but later an `index out of range` occurred.
And then `ModbusIOException: Modbus Error: [Input/Output] Unable to decode request` was raised in `_process`.
Regardless, the root cause is that `checkFrame()` returning `False` should not trigger `resetFrame()`. It should just mean "we don't have a full frame yet, wait for more data".
Let's write a reproduction script. I'll use a simple `asyncio` server to send the split packet.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport asyncio\nimport struct\nfrom pymodbus.client import AsyncModbusTcpClient\nfrom pymodbus.framer import ModbusSocketFramer\n\nasync def run_test():\n server = await asyncio.start_server(handle_client, '127.0.0.1', 5502)\n async with server:\n async with AsyncModbusTcpClient(host='127.0.0.1', port=5502) as client:\n # We expect this to fail with ModbusIOException or ConnectionException\n try:\n # Read holding registers\n # The server will send the response in two parts\n response = await client.read_holding_registers(42109, 4, slave=1)\n print(f\"Response: {response}\")\n except Exception as e:\n print(f\"Caught exception: {type(e).__name__}: {e}\")\n\nasync def handle_client(reader, writer):\n data = await reader.read(1024)\n # Response: TID=1, PID=0, Len=11, UID=1, FC=3, ByteCount=8, Data=8 bytes\n # Total 16 bytes.\n # Frame 1: first 15 bytes\n frame1 = struct.pack(\">HHHB\", 1, 0, 11, 1) + struct.pack(\">BB\", 3, 8) + b'\\x00\\xb5\\x12\\x2f\\x37\\x21\\x00'\n # Frame 2: last 1 byte\n frame2 = b'\\x03'\n \n writer.write(frame1)\n await writer.drain()\n await asyncio.sleep(0.1) # Ensure they are separate packets\n writer.write(frame2)\n await writer.drain()\n writer.close()\n await writer.wait_closed()\n\nif __name__ == \"__main__\":\n asyncio.run(run_test())\nPY\n"
}Result of run_command 1,542 characters
{
"status": "ok",
"stdout": "Caught exception: ConnectionException: Modbus Error: [Connection] Connection lost during request\n",
"stderr": "General exception: index out of range\nFatal error: protocol.data_received() call failed.\nprotocol: <pymodbus.client.tcp.AsyncModbusTcpClient object at 0x77a889744730>\ntransport: <_SelectorSocketTransport fd=7 read=polling write=<idle, bufsize=0>>\nTraceback (most recent call last):\n File \"/usr/local/lib/python3.10/asyncio/selector_events.py\", line 876, in _read_ready__data_received\n self._protocol.data_received(data)\n File \"/workspace/pymodbus/transport/transport.py\", line 318, in data_received\n self.datagram_received(data, None)\n File \"/workspace/pymodbus/transport/transport.py\", line 352, in datagram_received\n cut = self.callback_data(self.recv_buffer, addr=addr)\n File \"/workspace/pymodbus/client/base.py\", line 186, in callback_data\n self.framer.processIncomingPacket(data, self._handle_response, slave=0)\n File \"/workspace/pymodbus/framer/base.py\", line 139, in processIncomingPacket\n self.frameProcessIncomingPacket(single, callback, slave, **kwargs)\n File \"/workspace/pymodbus/framer/socket_framer.py\", line 136, in frameProcessIncomingPacket\n self._process(callback, tid, error=True)\n File \"/workspace/pymodbus/framer/socket_framer.py\", line 154, in _process\n raise ModbusIOException(\"Unable to decode request\")\npymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] Unable to decode request\n",
"exit_code": 0
}Generated tokens 3,688 tokens · stopped: STOP
Now let's analyze `ModbusSocketFramer.frameProcessIncomingPacket`:
```python
def frameProcessIncomingPacket(self, single, callback, slave, tid=None, **kwargs):
"""Process new packet pattern.
This takes in a new request packet, adds it to the current
packet stream, and performs framing on it. That is, checks
for complete messages, and once found, will process all that
exist. This handles the case when we read N + 1 or 1 // N
messages at a time instead of 1.
The processed and decoded messages are pushed to the callback
function to process and send.
"""
while True:
if not self.isFrameReady():
if len(self._buffer):
# Possible error ???
if self._header["len"] < 2:
self._process(callback, tid, error=True)
break
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
if not self._validate_slave_id(slave, single):
header_txt = self._header["uid"]
Log.debug("Not a valid slave id - {}, ignoring!!", header_txt)
self.resetFrame()
continue
self._process(callback, tid)
```
And `isFrameReady`:
```python
def isFrameReady(self):
"""Check if we should continue decode logic.
This is meant to be used in a while loop in the decoding phase to let
the decoder factory know that there is still data in the buffer.
:returns: True if ready, False otherwise
"""
return len(self._buffer) > self._hsize
```
`self._hsize` is `0x07` (7 bytes), which is the size of the MBAP header (tid 2, pid 2, len 2, uid 1).
And `checkFrame`:
```python
def checkFrame(self):
"""Check and decode the next frame.
Return true if we were successful.
"""
if self.isFrameReady():
(
self._header["tid"],
self._header["pid"],
self._header["len"],
self._header["uid"],
) = struct.unpack(">HHHB", self._buffer[0 : self._hsize])
# someone sent us an error? ignore it
if self._header["len"] < 2:
self.advanceFrame()
# we have at least a complete message, continue
elif len(self._buffer) - self._hsize + 1 >= self._header["len"]:
return True
# we don't have enough of a message yet, wait
return False
```
Wait, I see the problem. If `checkFrame()` returns `False`, `frameProcessIncomingPacket` does this:
```python
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
```
`self.resetFrame()` clears `self._buffer`!
```python
def resetFrame(self):
# ...
self._buffer = b""
# ...
```
So if `checkFrame()` returns `False` (meaning the full frame hasn't arrived yet), it wipes the buffer and starts over. This is exactly what the problem description says: "pymodbus doesn't seem to reassemble the modbus frames and instead tries parsing the first frame as a modbus response which it discards because it doesn't pass the Frame check."
The fix should be that if `checkFrame()` returns `False`, it should simply `break` the loop and wait for more data, rather than calling `resetFrame()` and `continue`.
Let's verify this with a reproduction script.
I will create a mock server that sends a Modbus TCP response in two pieces.
MBAP Header:
TID: 1 (2 bytes) -> \x00\x01
PID: 0 (2 bytes) -> \x00\x00
Length: 6 (2 bytes) -> \x00\x06 (Length is UID + PDU)
UID: 1 (1 byte) -> \x01
PDU: Function code 3, Data length 8, Data (8 bytes) = 1 + 1 + 8 = 10 bytes? No, length is from UID.
Wait, let's look at the MBAP header format:
[ tid 2b ][ pid 2b ][ length 2b ][ uid 1b ]
Length is the number of bytes following the length field. So `length = uid + pdu_length`.
Example: UID (1 byte) + Function Code (1 byte) + Byte Count (1 byte) + Data (N bytes).
Total = 1 + 1 + 1 + N bytes.
In the user's logs:
`recv: 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`
TID: 0x0001
PID: 0x0000
Length: 0x000b (11 decimal)
UID: 0x01
PDU: 0x03 (Read Holding Registers), 0x08 (Byte count), 0x00 0xb5 0x12 0x2f 0x37 0x21 0x00 (Wait, 0x00 0xb5 is 2 bytes, 0x12 0x2f is 2 bytes, 0x37 0x21 is 2 bytes, 0x00 is 1 byte. That's 7 bytes).
Total PDU = 1 (FC) + 1 (Byte count) + 7 (Data) = 9 bytes.
UID (1) + PDU (9) = 10 bytes.
Wait, the log says length is 0x0b (11).
Maybe the PDU is 10 bytes?
Let's count the bytes in `0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`.
`0x1` (UID)
`0x3` (FC)
`0x8` (Byte count)
`0x0`
`0xb5`
`0x12`
`0x2f`
`0x37`
`0x21`
`0x0`
Total: 10 bytes.
Wait, the log says `recv: ... 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 ...`
TID: 0, 1
PID: 0, 0
Length: 0, 11 (0x0b)
UID: 1
PDU: 3, 8, 0, 0xb5, 0x12, 0x2f, 0x37, 0x21, 0 (Wait, 0x0 is the 9th byte of PDU)
Wait, 11 bytes after Length field = UID(1) + PDU(10).
UID=1, PDU = 3, 8, 0, 0xb5, 0x12, 0x2f, 0x37, 0x21, 0, ...?
The log says `0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`
That's 16 bytes.
Header: 0, 1, 0, 0, 0, 11 (6 bytes)
Remaining: 1, 3, 8, 0, 0xb5, 0x12, 0x2f, 0x37, 0x21, 0 (10 bytes)
Total: 16 bytes.
So Length = 10. But the log says `0x0 0xb` (11).
Wait, `0 1 0 0 0 b`. `0x0b` is 11.
If length is 11, it expects 11 bytes after length.
`1 3 8 0 0xb5 0x12 0x2f 0x37 0x21 0` - that's 10 bytes.
So the 11th byte was sent in the next frame!
`recv: 0x3`
Exactly what the user said: "the second frame only contains the last required byte".
So we have:
Frame 1: MBAP header (Length=11), UID(1), PDU(9 bytes: FC=3, Len=8, Data=7 bytes). Total 15 bytes.
Frame 2: 1 byte (the 8th byte of data).
When Frame 1 arrives:
`isFrameReady()` returns `True` (len=15 > 7).
`checkFrame()`:
`self._header['len']` becomes 11.
`len(self._buffer) - self._hsize + 1` = `15 - 7 + 1` = 9.
Is `9 >= 11`? No.
So `checkFrame()` returns `False`.
Then `frameProcessIncomingPacket` calls `resetFrame()` and wipes the buffer.
Then Frame 2 arrives:
`isFrameReady()`: buffer now contains only `0x03` (1 byte). `1 > 7` is `False`.
Loop breaks.
Wait, if Frame 2 arrives and `isFrameReady` is False, it doesn't call `_process(callback, tid, error=True)` unless `self._header['len'] < 2`.
But `self._header` was reset!
Actually, in the logs:
`2024-01-04 11:16:16,635 DEBUG logging:103 Frame check failed, ignoring!!`
`2024-01-04 11:16:16,635 DEBUG logging:103 Resetting frame - Current Frame in buffer - 0x0 0x1 0x0 0x0 0x0 0xb 0x1 0x3 0x8 0x0 0xb5 0x12 0x2f 0x37 0x21 0x0`
`2024-01-04 11:16:16,719 DEBUG logging:103 recv: 0x3 old_data: addr=None`
`2024-01-04 11:16:16,719 DEBUG logging:103 Processing: 0x3`
`2024-01-04 11:16:16,719 DEBUG logging:103 Factory Response[ReadHoldingRegistersResponse': 3]`
`2024-01-04 11:16:16,719 ERROR logging:115 General exception: index out of range`
Wait, why did it try to parse `0x3` as a response?
In `processIncomingPacket`:
```python
def processIncomingPacket(self, data, callback, slave, **kwargs):
Log.debug("Processing: {}", data, ":hex")
self._buffer += data
if not isinstance(slave, (list, tuple)):
slave = [slave]
single = kwargs.pop("single", False)
self.frameProcessIncomingPacket(single, callback, slave, **kwargs)
```
When `0x03` arrives, `self._buffer` becomes `b'\x03'`.
Then `frameProcessIncomingPacket` is called.
`isFrameReady()` returns `False` (len=1 < 7).
```python
if not self.isFrameReady():
if len(self._buffer):
# Possible error ???
if self._header["len"] < 2:
self._process(callback, tid, error=True)
break
```
After `resetFrame()`, `self._header["len"]` is `0`.
So `0 < 2` is `True`.
It calls `self._process(callback, tid, error=True)`.
`_process` with `error=True` uses `data = self._buffer`.
So `data = b'\x03'`.
Then `self.decoder.decode(b'\x03')` is called.
Depending on the decoder, this might return something (like a response with function code 3) or throw an exception.
In the log, it seems it returned a `ReadHoldingRegistersResponse` object, but later an `index out of range` occurred.
And then `ModbusIOException: Modbus Error: [Input/Output] Unable to decode request` was raised in `_process`.
Regardless, the root cause is that `checkFrame()` returning `False` should not trigger `resetFrame()`. It should just mean "we don't have a full frame yet, wait for more data".
Let's write a reproduction script. I'll use a simple `asyncio` server to send the split packet.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import asyncio
import struct
from pymodbus.client import AsyncModbusTcpClient
from pymodbus.framer import ModbusSocketFramer
async def run_test():
server = await asyncio.start_server(handle_client, '127.0.0.1', 5502)
async with server:
async with AsyncModbusTcpClient(host='127.0.0.1', port=5502) as client:
# We expect this to fail with ModbusIOException or ConnectionException
try:
# Read holding registers
# The server will send the response in two parts
response = await client.read_holding_registers(42109, 4, slave=1)
print(f"Response: {response}")
except Exception as e:
print(f"Caught exception: {type(e).__name__}: {e}")
async def handle_client(reader, writer):
data = await reader.read(1024)
# Response: TID=1, PID=0, Len=11, UID=1, FC=3, ByteCount=8, Data=8 bytes
# Total 16 bytes.
# Frame 1: first 15 bytes
frame1 = struct.pack(">HHHB", 1, 0, 11, 1) + struct.pack(">BB", 3, 8) + b'\x00\xb5\x12\x2f\x37\x21\x00'
# Frame 2: last 1 byte
frame2 = b'\x03'
writer.write(frame1)
await writer.drain()
await asyncio.sleep(0.1) # Ensure they are separate packets
writer.write(frame2)
await writer.drain()
writer.close()
await writer.wait_closed()
if __name__ == "__main__":
asyncio.run(run_test())
PY
<|"|>}<tool_call|>('').<|tool_response>
Turn 7at 376 s1,152 tokens out14,623 prompt tokens
The reproduction confirms the issue.
The traceback shows:
`File "/workspace/pymodbus/framer/socket_framer.py", line 136, in frameProcessIncomingPacket`
`self._process(callback, tid, error=True)`
`File "/workspace/pymodbus/framer/socket_framer.py", line 154, in _process`
`raise ModbusIOException("Unable to decode request")`
This is exactly the behavior described.
Now let's fix it in `pymodbus/framer/socket_framer.py`.
I need to change:
```python
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
```
to:
```python
if not self.checkFrame():
# Not enough data for a full frame yet
break
```
Wait, should it be `break` or `continue`?
If `checkFrame()` returns `False`, it means we've read the header (if `isFrameReady` was true) but we haven't received the full payload yet.
Since `self._buffer` is only appended to in `processIncomingPacket`, and we are in a `while True` loop in `frameProcessIncomingPacket`, if we don't have enough data for the current frame, we cannot process any more frames in the buffer either. So we should `break` the loop and wait for more data to be added to `self._buffer`.
Let's check `isFrameReady()` again.
```python
def isFrameReady(self):
return len(self._buffer) > self._hsize
```
If `len(self._buffer)` is <= `self._hsize`, it breaks the loop.
If `len(self._buffer)` > `self._hsize`, it calls `checkFrame()`.
If `checkFrame()` returns `False`, it means we have the header but not the full body.
In that case, any further data in the buffer (if any) would be part of the current frame. So `break` is correct.
Wait, what if there is an actual error in the frame? The current code just wipes the buffer.
The `checkFrame` method:
```python
def checkFrame(self):
if self.isFrameReady():
(
self._header["tid"],
self._header["pid"],
self._header["len"],
self._header["uid"],
) = struct.unpack(">HHHB", self._buffer[0 : self._hsize])
# someone sent us an error? ignore it
if self._header["len"] < 2:
self.advanceFrame()
# we have at least a complete message, continue
elif len(self._buffer) - self._hsize + 1 >= self._header["len"]:
return True
return False
```
If `self._header["len"] < 2`, it calls `advanceFrame()` and returns `False`.
`advanceFrame` does:
```python
def advanceFrame(self):
length = self._hsize + self._header["len"] - 1
self._buffer = self._buffer[length:]
self._header = {"tid": 0, "pid": 0, "len": 0, "uid": 0}
```
And then `frameProcessIncomingPacket` calls `resetFrame()` and wipes the buffer.
If `self._header["len"] < 2`, it means the received length is invalid (too short). In this case, skipping the invalid frame (advanceFrame) and then resetting is probably too aggressive but maybe acceptable if the stream is corrupted. But the main issue is the `elif` case where we just don't have enough data yet.
If `len(self._buffer) - self._hsize + 1 < self._header["len"]`, it returns `False`. This is the case of partial frame.
So the fix is indeed to `break` instead of `resetFrame()` and `continue`.
Wait, should I also remove the `Log.debug("Frame check failed, ignoring!!")`? It's misleading if it's just a partial frame.
Let's see what happens if I change:
```python
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
```
to
```python
if not self.checkFrame():
break
```
Let's also check if this affects any other framers. `socket_framer.py` is for Modbus TCP. Modbus TCP is a stream-based protocol, so reassembly is essential.
Let's implement the fix.
TOOL CALL · edit_file
{
"filepath": "pymodbus/framer/socket_framer.py",
"new_string": " if not self.checkFrame():\n break",
"old_string": " if not self.checkFrame():\n Log.debug(\"Frame check failed, ignoring!!\")\n self.resetFrame()\n continue"
}Result of edit_file 718 characters
{
"status": "ok",
"filepath": "pymodbus/framer/socket_framer.py",
"occurrences": 1,
"strategy": "exact",
"diff": "--- a/pymodbus/framer/socket_framer.py\n+++ b/pymodbus/framer/socket_framer.py\n@@ -136,9 +136,7 @@\n self._process(callback, tid, error=True)\n break\n if not self.checkFrame():\n- Log.debug(\"Frame check failed, ignoring!!\")\n- self.resetFrame()\n- continue\n+ break\n if not self._validate_slave_id(slave, single):\n header_txt = self._header[\"uid\"]\n Log.debug(\"Not a valid slave id - {}, ignoring!!\", header_txt)\n",
"is_truncated": false
}Generated tokens 1,152 tokens · stopped: STOP
The reproduction confirms the issue.
The traceback shows:
`File "/workspace/pymodbus/framer/socket_framer.py", line 136, in frameProcessIncomingPacket`
`self._process(callback, tid, error=True)`
`File "/workspace/pymodbus/framer/socket_framer.py", line 154, in _process`
`raise ModbusIOException("Unable to decode request")`
This is exactly the behavior described.
Now let's fix it in `pymodbus/framer/socket_framer.py`.
I need to change:
```python
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
```
to:
```python
if not self.checkFrame():
# Not enough data for a full frame yet
break
```
Wait, should it be `break` or `continue`?
If `checkFrame()` returns `False`, it means we've read the header (if `isFrameReady` was true) but we haven't received the full payload yet.
Since `self._buffer` is only appended to in `processIncomingPacket`, and we are in a `while True` loop in `frameProcessIncomingPacket`, if we don't have enough data for the current frame, we cannot process any more frames in the buffer either. So we should `break` the loop and wait for more data to be added to `self._buffer`.
Let's check `isFrameReady()` again.
```python
def isFrameReady(self):
return len(self._buffer) > self._hsize
```
If `len(self._buffer)` is <= `self._hsize`, it breaks the loop.
If `len(self._buffer)` > `self._hsize`, it calls `checkFrame()`.
If `checkFrame()` returns `False`, it means we have the header but not the full body.
In that case, any further data in the buffer (if any) would be part of the current frame. So `break` is correct.
Wait, what if there is an actual error in the frame? The current code just wipes the buffer.
The `checkFrame` method:
```python
def checkFrame(self):
if self.isFrameReady():
(
self._header["tid"],
self._header["pid"],
self._header["len"],
self._header["uid"],
) = struct.unpack(">HHHB", self._buffer[0 : self._hsize])
# someone sent us an error? ignore it
if self._header["len"] < 2:
self.advanceFrame()
# we have at least a complete message, continue
elif len(self._buffer) - self._hsize + 1 >= self._header["len"]:
return True
return False
```
If `self._header["len"] < 2`, it calls `advanceFrame()` and returns `False`.
`advanceFrame` does:
```python
def advanceFrame(self):
length = self._hsize + self._header["len"] - 1
self._buffer = self._buffer[length:]
self._header = {"tid": 0, "pid": 0, "len": 0, "uid": 0}
```
And then `frameProcessIncomingPacket` calls `resetFrame()` and wipes the buffer.
If `self._header["len"] < 2`, it means the received length is invalid (too short). In this case, skipping the invalid frame (advanceFrame) and then resetting is probably too aggressive but maybe acceptable if the stream is corrupted. But the main issue is the `elif` case where we just don't have enough data yet.
If `len(self._buffer) - self._hsize + 1 < self._header["len"]`, it returns `False`. This is the case of partial frame.
So the fix is indeed to `break` instead of `resetFrame()` and `continue`.
Wait, should I also remove the `Log.debug("Frame check failed, ignoring!!")`? It's misleading if it's just a partial frame.
Let's see what happens if I change:
```python
if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue
```
to
```python
if not self.checkFrame():
break
```
Let's also check if this affects any other framers. `socket_framer.py` is for Modbus TCP. Modbus TCP is a stream-based protocol, so reassembly is essential.
Let's implement the fix.
<channel|><|tool_call>call:edit_file{filepath:<|"|>pymodbus/framer/socket_framer.py<|"|>,new_string:<|"|> if not self.checkFrame():
break<|"|>,old_string:<|"|> if not self.checkFrame():
Log.debug("Frame check failed, ignoring!!")
self.resetFrame()
continue<|"|>}<tool_call|><|tool_response>
Turn 8at 457 s492 tokens out9,410 prompt tokens
Now let's run the reproduction script again to verify the fix.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport asyncio\nimport struct\nfrom pymodbus.client import AsyncModbusTcpClient\nfrom pymodbus.framer import ModbusSocketFramer\n\nasync def run_test():\n server = await asyncio.start_server(handle_client, '127.0.0.1', 5502)\n async with server:\n async with AsyncModbusTcpClient(host='127.0.0.1', port=5502) as client:\n try:\n # Read holding registers\n # The server will send the response in two parts\n response = await client.read_holding_registers(42109, 4, slave=1)\n print(f\"Response: {response}\")\n except Exception as e:\n print(f\"Caught exception: {type(e).__name__}: {e}\")\n\nasync def handle_client(reader, writer):\n data = await reader.read(1024)\n # Response: TID=1, PID=0, Len=11, UID=1, FC=3, ByteCount=8, Data=8 bytes\n # Total 16 bytes.\n # Frame 1: first 15 bytes\n frame1 = struct.pack(\">HHHB\", 1, 0, 11, 1) + struct.pack(\">BB\", 3, 8) + b'\\x00\\xb5\\x12\\x2f\\x37\\x21\\x00'\n # Frame 2: last 1 byte\n frame2 = b'\\x03'\n \n writer.write(frame1)\n await writer.drain()\n await asyncio.sleep(0.1) # Ensure they are separate packets\n writer.write(frame2)\n await writer.drain()\n writer.close()\n await writer.wait_closed()\n\nif __name__ == \"__main__\":\n asyncio.run(run_test())\nPY\n"
}Result of run_command 104 characters
{
"status": "ok",
"stdout": "Response: ReadHoldingRegistersResponse (4)\n",
"stderr": "",
"exit_code": 0
}Generated tokens 492 tokens · stopped: STOP
Now let's run the reproduction script again to verify the fix.<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import asyncio
import struct
from pymodbus.client import AsyncModbusTcpClient
from pymodbus.framer import ModbusSocketFramer
async def run_test():
server = await asyncio.start_server(handle_client, '127.0.0.1', 5502)
async with server:
async with AsyncModbusTcpClient(host='127.0.0.1', port=5502) as client:
try:
# Read holding registers
# The server will send the response in two parts
response = await client.read_holding_registers(42109, 4, slave=1)
print(f"Response: {response}")
except Exception as e:
print(f"Caught exception: {type(e).__name__}: {e}")
async def handle_client(reader, writer):
data = await reader.read(1024)
# Response: TID=1, PID=0, Len=11, UID=1, FC=3, ByteCount=8, Data=8 bytes
# Total 16 bytes.
# Frame 1: first 15 bytes
frame1 = struct.pack(">HHHB", 1, 0, 11, 1) + struct.pack(">BB", 3, 8) + b'\x00\xb5\x12\x2f\x37\x21\x00'
# Frame 2: last 1 byte
frame2 = b'\x03'
writer.write(frame1)
await writer.drain()
await asyncio.sleep(0.1) # Ensure they are separate packets
writer.write(frame2)
await writer.drain()
writer.close()
await writer.wait_closed()
if __name__ == "__main__":
asyncio.run(run_test())
PY
<|"|>}<tool_call|><|tool_response>
Turn 9at 464 s78 tokens out9,951 prompt tokens
The reproduction script now passes! "Response: ReadHoldingRegistersResponse (4)". Now I should run the existing tests for `socket_framer.py` to make sure I didn't break anything. First, let's find the tests.
TOOL CALL · run_command
{
"command": "grep -rn \"SocketFramer\" tests/"
}Result of run_command 209 characters
{
"status": "error",
"error_type": "CommandError",
"error_message": "grep: tests/: No such file or directory\n",
"details": {
"stdout": "",
"stderr": "grep: tests/: No such file or directory\n",
"exit_code": 2
}
}Generated tokens 78 tokens · stopped: STOP
The reproduction script now passes! "Response: ReadHoldingRegistersResponse (4)".
Now I should run the existing tests for `socket_framer.py` to make sure I didn't break anything.
First, let's find the tests.<channel|><|tool_call>call:run_command{command:<|"|>grep -rn "SocketFramer" tests/<|"|>}<tool_call|><|tool_response>
Turn 10at 466 s35 tokens out10,109 prompt tokens
Ah, maybe the tests are in `test/`?
TOOL CALL · run_command
{
"command": "find . -name \"*test*\""
}Result of run_command 1,552 characters
{
"status": "ok",
"stdout": "./test\n./test/test_events.py\n./test/test_remote_datastore.py\n./test/sub_transport/test_nullmodem.py\n./test/sub_transport/test_protocol.py\n./test/sub_transport/test_reconnect.py\n./test/sub_transport/test_basic.py\n./test/sub_transport/test_comm.py\n./test/sub_transport/conftest.py\n./test/test_logging.py\n./test/test_file_message.py\n./test/test_factory.py\n./test/test_exceptions.py\n./test/test_payload.py\n./test/test_sparse_datastore.py\n./test/test_framers.py\n./test/sub_client/test_repl_client.py\n./test/sub_client/test_client_sync.py\n./test/sub_client/test_client.py\n./test/sub_client/test_client_faulty_response.py\n./test/test_utilities.py\n./test/test_device.py\n./test/sub_messages/test_register_read_messages.py\n./test/sub_messages/test_all_messages.py\n./test/sub_messages/test_bit_write_messages.py\n./test/sub_messages/test_mei_messages.py\n./test/sub_messages/test_diag_messages.py\n./test/sub_messages/test_other_messages.py\n./test/sub_messages/test_bit_read_messages.py\n./test/sub_messages/test_register_write_messages.py\n./test/conftest.py\n./test/sub_server/test_simulator.py\n./test/sub_server/test_server_multidrop.py\n./test/sub_server/test_server_asyncio.py\n./test/sub_server/test_server_context.py\n./test/test_pdu.py\n./test/test_transaction.py\n./test/sub_examples/test_helper.py\n./test/sub_examples/test_examples.py\n./test/sub_examples/test_client_server_async.py\n./test/sub_examples/test_client_server_sync.py\n./test/sub_examples/conftest.py\n",
"stderr": "",
"exit_code": 0
}Generated tokens 35 tokens · stopped: STOP
Ah, maybe the tests are in `test/`?
<channel|><|tool_call>call:run_command{command:<|"|>find . -name "*test*"<|"|>}<tool_call|><|tool_response>
Patch, tests and logs
Final code change Included
diff --git a/pymodbus/framer/socket_framer.py b/pymodbus/framer/socket_framer.py
index 7f55eea..206dd80 100644
--- a/pymodbus/framer/socket_framer.py
+++ b/pymodbus/framer/socket_framer.py
@@ -136,9 +136,7 @@ class ModbusSocketFramer(ModbusFramer):
self._process(callback, tid, error=True)
break
if not self.checkFrame():
- Log.debug("Frame check failed, ignoring!!")
- self.resetFrame()
- continue
+ break
if not self._validate_slave_id(slave, single):
header_txt = self._header["uid"]
Log.debug("Not a valid slave id - {}, ignoring!!", header_txt)
Test output Included
============================= test session starts ============================== created: 48/48 workers 48 workers [48 items] ...............................................F [100%] =================================== FAILURES =================================== [gw0] linux -- Python 3.10.19 /usr/local/bin/python E pymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] Unable to decode request ------------------------------ Captured log call ------------------------------- ERROR pymodbus.logging:logging.py:115 Unable to decode response Modbus Error: Unknown response 0 /pymodbus/pymodbus/framer/socket_framer.py:152: pymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] Unable to decode request ==================================== PASSES ==================================== _________________________________ test_process _________________________________ [gw0] linux -- Python 3.10.19 /usr/local/bin/python ------------------------------ Captured log call ------------------------------- ERROR pymodbus.logging:logging.py:115 General exception: index out of range - generated xml file: /tmp/rebench-grade-d844b2795a514c2e829f38a675209209.xml -- =========================== short test summary info ============================ PASSED test/test_framers.py::test_framer_initialization[ModbusRtuFramer] PASSED test/test_framers.py::test_framer_initialization[ModbusAsciiFramer] PASSED test/test_framers.py::test_framer_initialization[ModbusBinaryFramer] PASSED test/test_framers.py::test_decode_data[data0] PASSED test/test_framers.py::test_decode_data[data1] PASSED test/test_framers.py::test_check_frame[data0] PASSED test/test_framers.py::test_check_frame[data1] PASSED test/test_framers.py::test_check_frame[data2] PASSED test/test_framers.py::test_check_frame[data3] PASSED test/test_framers.py::test_rtu_advance_framer[data0] PASSED test/test_framers.py::test_rtu_advance_framer[data1] PASSED test/test_framers.py::test_rtu_advance_framer[data2] PASSED test/test_framers.py::test_rtu_reset_framer[] PASSED test/test_framers.py::test_rtu_reset_framer[abcd] PASSED test/test_framers.py::test_is_frame_ready[data0] PASSED test/test_framers.py::test_is_frame_ready[data1] PASSED test/test_framers.py::test_is_frame_ready[data2] PASSED test/test_framers.py::test_is_frame_ready[data3] PASSED test/test_framers.py::test_is_frame_ready[data4] PASSED test/test_framers.py::test_is_frame_ready[data5] PASSED test/test_framers.py::test_is_frame_ready[data6] PASSED test/test_framers.py::test_rtu_populate_header_fail[] PASSED test/test_framers.py::test_rtu_populate_header_fail[\x11] PASSED test/test_framers.py::test_rtu_populate_header_fail[\x11\x03] PASSED test/test_framers.py::test_rtu_populate_header_fail[\x11\x03\x06] PASSED test/test_framers.py::test_rtu_populate_header_fail[\x11\x03\x06\xaeAVRC@C] PASSED test/test_framers.py::test_rtu_populate_header[data0] PASSED test/test_framers.py::test_rtu_populate_header[data1] PASSED test/test_framers.py::test_get_frame PASSED test/test_framers.py::test_populate_result PASSED test/test_framers.py::test_rtu_incoming_packet[data0] PASSED test/test_framers.py::test_rtu_incoming_packet[data1] PASSED test/test_framers.py::test_rtu_incoming_packet[data2] PASSED test/test_framers.py::test_rtu_incoming_packet[data3] PASSED test/test_framers.py::test_rtu_incoming_packet[data4] PASSED test/test_framers.py::test_rtu_incoming_packet[data5] PASSED test/test_framers.py::test_rtu_incoming_packet[data6] PASSED test/test_framers.py::test_rtu_incoming_packet[data7] PASSED test/test_framers.py::test_rtu_incoming_packet[data8] PASSED test/test_framers.py::test_rtu_incoming_packet[data9] PASSED test/test_framers.py::test_build_packet PASSED test/test_framers.py::test_send_packet PASSED test/test_framers.py::test_recv_packet PASSED test/test_framers.py::test_process PASSED test/test_framers.py::test_validate__slave_id PASSED test/test_framers.py::test_decode_ascii_data[:010100010001FC\r\n] PASSED test/test_framers.py::test_decode_ascii_data[] FAILED test/test_framers.py::test_recv_split_packet - pymodbus.exceptions.Mod... ======================== 1 failed, 47 passed in 11.39s =========================
Test errors Included
Test report (JUnit) Included
<?xml version="1.0" encoding="utf-8"?><testsuites name="pytest tests"><testsuite name="pytest" errors="0" failures="1" skipped="0" tests="48" time="11.392" timestamp="2026-11-14T03:32:29.658911+00:00" hostname="53ba35b4564e"><testcase classname="test.test_framers" name="test_framer_initialization[ModbusRtuFramer]" time="0.198" /><testcase classname="test.test_framers" name="test_framer_initialization[ModbusAsciiFramer]" time="0.202" /><testcase classname="test.test_framers" name="test_framer_initialization[ModbusBinaryFramer]" time="0.102" /><testcase classname="test.test_framers" name="test_decode_data[data0]" time="0.196" /><testcase classname="test.test_framers" name="test_decode_data[data1]" time="0.102" /><testcase classname="test.test_framers" name="test_check_frame[data0]" time="0.102" /><testcase classname="test.test_framers" name="test_check_frame[data1]" time="0.102" /><testcase classname="test.test_framers" name="test_check_frame[data2]" time="0.103" /><testcase classname="test.test_framers" name="test_check_frame[data3]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_advance_framer[data0]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_advance_framer[data1]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_advance_framer[data2]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_reset_framer[]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_reset_framer[abcd]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data0]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data1]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data2]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data3]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data4]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data5]" time="0.101" /><testcase classname="test.test_framers" name="test_is_frame_ready[data6]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_populate_header_fail[]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_populate_header_fail[\x11]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_populate_header_fail[\x11\x03]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_populate_header_fail[\x11\x03\x06]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_populate_header_fail[\x11\x03\x06\xaeAVRC@C]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_populate_header[data0]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_populate_header[data1]" time="0.101" /><testcase classname="test.test_framers" name="test_get_frame" time="0.101" /><testcase classname="test.test_framers" name="test_populate_result" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data0]" time="0.110" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data1]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data2]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data3]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data4]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data5]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data6]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data7]" time="0.102" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data8]" time="0.101" /><testcase classname="test.test_framers" name="test_rtu_incoming_packet[data9]" time="0.102" /><testcase classname="test.test_framers" name="test_build_packet" time="0.101" /><testcase classname="test.test_framers" name="test_send_packet" time="1.103" /><testcase classname="test.test_framers" name="test_recv_packet" time="0.101" /><testcase classname="test.test_framers" name="test_process" time="0.101" /><testcase classname="test.test_framers" name="test_validate__slave_id" time="0.101" /><testcase classname="test.test_framers" name="test_decode_ascii_data[:010100010001FC\r\n]" time="0.101" /><testcase classname="test.test_framers" name="test_decode_ascii_data[]" time="0.101" /><testcase classname="test.test_framers" name="test_recv_split_packet" time="0.101"><failure message="pymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] Unable to decode request">E pymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] Unable to decode request</failure></testcase></testsuite></testsuites>
Agent log Included
[ 0.0s] 📋 System Prompt: You are a principal Python software engineer resolving a repository issue in `/workspace`.
[ 0.0s] 🎯 Task Prompt: You are evaluating a software engineering task for repository pymodbus-dev/pymodbus.
[ 27.4s] 💭 (1025 chars) "The user is reporting an issue where `pymodbus` fails to handle reassembled TCP segments.
Specifically, when a Modbus re..."
[ 27.4s] 🔧 run_command grep -rn --include="*.py" "processIncomingPacket" pymodbus/framer/socket_framer.
[ 27.5s] → pymodbus/framer/base.py:115: def processIncomingPacket(self, data, callback, slave, **kwargs):
[ 40.9s] 💭 (540 chars) "Wait, `grep` didn't show `processIncomingPacket` in `socket_framer.py` but the traceback
said:
`File "/home/simon/tools/..."
[ 40.9s] 🔧 run_command grep -rn --include="*.py" "frameProcessIncomingPacket" pymodbus/framer/socket_fr
[ 41.0s] → 119: def frameProcessIncomingPacket(self, single, callback, slave, tid=None, **kwargs):
[ 44.7s] 💭 (142 chars) "Okay, so `SocketFramer.frameProcessIncomingPacket` is the place.
Let's read `pymodbus/framer/socket_framer.py` and `pym..."
[ 44.7s] 📖 read_file (pymodbus/framer/socket_framer.py)
[ 44.8s] ✓ {'status': 'ok', 'filepath': 'pymodbus/framer/socket_framer.py', 'content': '"""Socket framer."""\n#
pylint: disable=mis…
[ 49.4s] 💭 (97 chars) "I need to read the rest of `pymodbus/framer/socket_framer.py` to see `_process` and
`resetFrame`."
[ 49.4s] 📖 read_file (pymodbus/framer/socket_framer.py)
[ 49.4s] ✓ {'status': 'ok', 'filepath': 'pymodbus/framer/socket_framer.py', 'content': ' data = self._buffer
if error else s…
[ 54.2s] 💭 (171 chars) "Wait, I don't see `resetFrame()` implementation in `ModbusSocketFramer`. It must be in
`ModbusFramer` in `pymodbus/frame..."
[ 54.2s] 📖 read_file (pymodbus/framer/base.py)
[ 54.3s] ✓ {'status': 'ok', 'filepath': 'pymodbus/framer/base.py', 'content': '"""Framer start."""\n# pylint:
disable=missing-type-…
[ 284.5s] 💭 (8813 chars) "Now let's analyze `ModbusSocketFramer.frameProcessIncomingPacket`:
```python
def frameProcessIncomingPacket(self, s..."
[ 284.5s] 🔧 run_command (39 lines) python3 - <<'PY'
[ 284.8s] → Caught exception: ConnectionException: Modbus Error: [Connection] Connection lost during request
[ 358.7s] 💭 (3936 chars) "The reproduction confirms the issue.
The traceback shows:
`File "/workspace/pymodbus/framer/socket_framer.py", line 136,..."
[ 358.7s] ✏️ edit_file (pymodbus/framer/socket_framer.py)
[ 358.9s] ✓ {'status': 'ok', 'filepath': 'pymodbus/framer/socket_framer.py', 'occurrences': 1, 'strategy': 'exact',
'diff': '--- a/p…
[ 440.1s] 💭 (62 chars) "Now let's run the reproduction script again to verify the fix."
[ 440.1s] 🔧 run_command (38 lines) python3 - <<'PY'
[ 440.3s] → Response: ReadHoldingRegistersResponse (4)
[ 446.5s] 💭 (208 chars) "The reproduction script now passes! "Response: ReadHoldingRegistersResponse (4)".
Now I should run the existing tests f..."
[ 446.5s] 🔧 run_command grep -rn "SocketFramer" tests/
[ 446.6s] → error (exit 0):
[ 448.6s] 💭 (35 chars) "Ah, maybe the tests are in `test/`?"
[ 448.6s] 🔧 run_command find . -name "*test*"
[ 448.6s] → ./test
Native result row
{
"agent_error": "Agent exceeded session timeout (7.5 min)",
"duration_seconds": 482.36,
"error": "Test failures/errors recorded in JUnit XML (failures=1, errors=0)",
"grade": {
"collected_tests": 48,
"competition_junit_ok": false,
"error": "Test failures/errors recorded in JUnit XML (failures=1, errors=0)",
"required_issues_count": 1,
"resolved": false,
"status_counts": {
"FAILED": 1,
"PASSED": 47
},
"strict_clean_patch": true,
"test_exit_code": 1
},
"instance_id": "pymodbus-dev__pymodbus-1923",
"pass_idx": 0,
"patch_chars": 712,
"phase1_seconds": 469.6,
"repo": "pymodbus-dev/pymodbus",
"request_log_path": "/kaggle-root/working/r31/rollouts_X/requests/pymodbus-dev__pymodbus-1923__p0__r6.jsonl",
"resolved": false,
"rollout_idx": 6,
"run_key": "pymodbus-dev__pymodbus-1923__p0__r6",
"strict_clean_patch": true,
"tool_calls": 10,
"total_llm_calls": 10,
"trace_path": "/kaggle-root/working/r31/rollouts_X/traces/trace_pymodbus-dev__pymodbus-1923__p0__r6.json"
}