276 lines
9.0 KiB
Python
276 lines
9.0 KiB
Python
"""Modbus client async TCP communication."""
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import asyncio
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import select
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import socket
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import time
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from typing import Any, Tuple, Type
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from pymodbus.client.base import ModbusBaseClient
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from pymodbus.exceptions import ConnectionException
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from pymodbus.framer import ModbusFramer
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from pymodbus.framer.socket_framer import ModbusSocketFramer
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from pymodbus.logging import Log
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from pymodbus.transport import CommType
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from pymodbus.utilities import ModbusTransactionState
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class AsyncModbusTcpClient(ModbusBaseClient, asyncio.Protocol):
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"""**AsyncModbusTcpClient**.
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:param host: Host IP address or host name
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:param port: (optional) Port used for communication
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:param framer: (optional) Framer class
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:param source_address: (optional) source address of client
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:param kwargs: (optional) Experimental parameters
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Example::
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from pymodbus.client import AsyncModbusTcpClient
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async def run():
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client = AsyncModbusTcpClient("localhost")
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await client.connect()
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...
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client.close()
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"""
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def __init__(
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self,
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host: str,
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port: int = 502,
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framer: Type[ModbusFramer] = ModbusSocketFramer,
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source_address: Tuple[str, int] = None,
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**kwargs: Any,
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) -> None:
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"""Initialize Asyncio Modbus TCP Client."""
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asyncio.Protocol.__init__(self)
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if "CommType" not in kwargs:
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kwargs["CommType"] = CommType.TCP
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if source_address:
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kwargs["source_address"] = source_address
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ModbusBaseClient.__init__(
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self,
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framer=framer,
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host=host,
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port=port,
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**kwargs,
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)
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self.params.source_address = source_address
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async def connect(self) -> bool:
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"""Initiate connection to start client."""
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self.reset_delay()
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Log.debug(
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"Connecting to {}:{}.",
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self.comm_params.host,
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self.comm_params.port,
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)
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return await self.transport_connect()
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@property
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def connected(self):
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"""Return true if connected."""
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return self.is_active()
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class ModbusTcpClient(ModbusBaseClient):
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"""**ModbusTcpClient**.
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:param host: Host IP address or host name
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:param port: (optional) Port used for communication
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:param framer: (optional) Framer class
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:param source_address: (optional) source address of client
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:param kwargs: (optional) Experimental parameters
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Example::
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from pymodbus.client import ModbusTcpClient
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async def run():
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client = ModbusTcpClient("localhost")
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client.connect()
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...
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client.close()
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Remark: There are no automatic reconnect as with AsyncModbusTcpClient
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"""
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def __init__(
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self,
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host: str,
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port: int = 502,
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framer: Type[ModbusFramer] = ModbusSocketFramer,
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source_address: Tuple[str, int] = None,
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**kwargs: Any,
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) -> None:
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"""Initialize Modbus TCP Client."""
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if "CommType" not in kwargs:
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kwargs["CommType"] = CommType.TCP
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kwargs["use_sync"] = True
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self.transport = None
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super().__init__(framer=framer, host=host, port=port, **kwargs)
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self.params.source_address = source_address
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self.socket = None
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@property
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def connected(self):
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"""Connect internal."""
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return self.socket is not None
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def connect(self): # pylint: disable=invalid-overridden-method
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"""Connect to the modbus tcp server."""
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if self.socket:
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return True
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try:
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self.socket = socket.create_connection(
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(self.comm_params.host, self.comm_params.port),
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timeout=self.comm_params.timeout_connect,
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source_address=self.params.source_address,
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)
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Log.debug(
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"Connection to Modbus server established. Socket {}",
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self.socket.getsockname(),
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)
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except OSError as msg:
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Log.error(
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"Connection to ({}, {}) failed: {}",
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self.comm_params.host,
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self.comm_params.port,
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msg,
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)
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self.close()
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return self.socket is not None
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def close(self): # pylint: disable=arguments-differ
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"""Close the underlying socket connection."""
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if self.socket:
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self.socket.close()
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self.socket = None
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def _check_read_buffer(self):
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"""Check read buffer."""
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time_ = time.time()
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end = time_ + self.comm_params.timeout_connect
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data = None
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ready = select.select([self.socket], [], [], end - time_)
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if ready[0]:
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data = self.socket.recv(1024)
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return data
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def send(self, request):
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"""Send data on the underlying socket."""
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super().send(request)
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if not self.socket:
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raise ConnectionException(str(self))
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if self.state == ModbusTransactionState.RETRYING:
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if data := self._check_read_buffer():
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return data
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if request:
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return self.socket.send(request)
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return 0
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def recv(self, size):
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"""Read data from the underlying descriptor."""
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super().recv(size)
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if not self.socket:
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raise ConnectionException(str(self))
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# socket.recv(size) waits until it gets some data from the host but
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# not necessarily the entire response that can be fragmented in
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# many packets.
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# To avoid split responses to be recognized as invalid
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# messages and to be discarded, loops socket.recv until full data
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# is received or timeout is expired.
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# If timeout expires returns the read data, also if its length is
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# less than the expected size.
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self.socket.setblocking(0)
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timeout = self.comm_params.timeout_connect
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# If size isn't specified read up to 4096 bytes at a time.
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if size is None:
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recv_size = 4096
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else:
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recv_size = size
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data = []
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data_length = 0
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time_ = time.time()
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end = time_ + timeout
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while recv_size > 0:
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try:
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ready = select.select([self.socket], [], [], end - time_)
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except ValueError:
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return self._handle_abrupt_socket_close(size, data, time.time() - time_)
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if ready[0]:
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if (recv_data := self.socket.recv(recv_size)) == b"":
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return self._handle_abrupt_socket_close(
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size, data, time.time() - time_
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)
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data.append(recv_data)
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data_length += len(recv_data)
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time_ = time.time()
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# If size isn't specified continue to read until timeout expires.
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if size:
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recv_size = size - data_length
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# Timeout is reduced also if some data has been received in order
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# to avoid infinite loops when there isn't an expected response
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# size and the slave sends noisy data continuously.
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if time_ > end:
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break
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return b"".join(data)
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def _handle_abrupt_socket_close(self, size, data, duration):
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"""Handle unexpected socket close by remote end.
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Intended to be invoked after determining that the remote end
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has unexpectedly closed the connection, to clean up and handle
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the situation appropriately.
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:param size: The number of bytes that was attempted to read
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:param data: The actual data returned
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:param duration: Duration from the read was first attempted
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until it was determined that the remote closed the
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socket
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:return: The more than zero bytes read from the remote end
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:raises ConnectionException: If the remote end didn't send any
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data at all before closing the connection.
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"""
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self.close()
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size_txt = size if size else "unbounded read"
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readsize = f"read of {size_txt} bytes"
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msg = (
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f"{self}: Connection unexpectedly closed "
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f"{duration} seconds into {readsize}"
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)
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if data:
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result = b"".join(data)
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Log.warning(" after returning {} bytes: {} ", len(result), result)
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return result
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msg += " without response from slave before it closed connection"
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raise ConnectionException(msg)
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def is_socket_open(self):
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"""Check if socket is open."""
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return self.socket is not None
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def __str__(self):
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"""Build a string representation of the connection.
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:returns: The string representation
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"""
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return f"ModbusTcpClient({self.comm_params.host}:{self.comm_params.port})"
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def __repr__(self):
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"""Return string representation."""
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return (
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f"<{self.__class__.__name__} at {hex(id(self))} socket={self.socket}, "
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f"ipaddr={self.comm_params.host}, port={self.comm_params.port}, timeout={self.comm_params.timeout_connect}>"
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)
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