"""Modbus client async TCP communication.""" from __future__ import annotations import select import socket import time from collections.abc import Callable from ssl import SSLWantReadError from pymodbus.client.base import ModbusBaseClient, ModbusBaseSyncClient from pymodbus.exceptions import ConnectionException from pymodbus.framer import FramerType from pymodbus.logging import Log from pymodbus.pdu import ModbusPDU from pymodbus.transport import CommParams, CommType class AsyncModbusTcpClient(ModbusBaseClient): """**AsyncModbusTcpClient**. Fixed parameters: :param host: Host IP address or host name Optional parameters: :param framer: Framer name, default FramerType.SOCKET :param port: Port used for communication :param name: Set communication name, used in logging :param source_address: source address of client :param reconnect_delay: Minimum delay in seconds.milliseconds before reconnecting. :param reconnect_delay_max: Maximum delay in seconds.milliseconds before reconnecting. :param timeout: Timeout for connecting and receiving data, in seconds. :param retries: Max number of retries per request. :param trace_packet: Called with bytestream received/to be sent :param trace_pdu: Called with PDU received/to be sent :param trace_connect: Called when connected/disconnected .. tip:: The trace methods allow to modify the datastream/pdu ! .. tip:: **reconnect_delay** doubles automatically with each unsuccessful connect, from **reconnect_delay** to **reconnect_delay_max**. Set `reconnect_delay=0` to avoid automatic reconnection. Example:: from pymodbus.client import AsyncModbusTcpClient async def run(): client = AsyncModbusTcpClient("localhost") await client.connect() ... client.close() Please refer to :ref:`Pymodbus internals` for advanced usage. """ def __init__( # pylint: disable=too-many-arguments self, host: str, *, framer: FramerType = FramerType.SOCKET, port: int = 502, name: str = "comm", source_address: tuple[str, int] | None = None, reconnect_delay: float = 0.1, reconnect_delay_max: float = 300, timeout: float = 3, retries: int = 3, trace_packet: Callable[[bool, bytes], bytes] | None = None, trace_pdu: Callable[[bool, ModbusPDU], ModbusPDU] | None = None, trace_connect: Callable[[bool], None] | None = None, ) -> None: """Initialize Asyncio Modbus TCP Client.""" if not hasattr(self,"comm_params"): if framer not in [FramerType.SOCKET, FramerType.RTU, FramerType.ASCII]: raise TypeError("Only FramerType SOCKET/RTU/ASCII allowed.") self.comm_params = CommParams( comm_type=CommType.TCP, host=host, port=port, comm_name=name, source_address=source_address, reconnect_delay=reconnect_delay, reconnect_delay_max=reconnect_delay_max, timeout_connect=timeout, ) ModbusBaseClient.__init__( self, framer, retries, self.comm_params, trace_packet, trace_pdu, trace_connect, ) class ModbusTcpClient(ModbusBaseSyncClient): """**ModbusTcpClient**. Fixed parameters: :param host: Host IP address or host name Optional parameters: :param framer: Framer name, default FramerType.SOCKET :param port: Port used for communication :param name: Set communication name, used in logging :param source_address: source address of client :param reconnect_delay: Not used in the sync client :param reconnect_delay_max: Not used in the sync client :param timeout: Timeout for connecting and receiving data, in seconds. :param retries: Max number of retries per request. :param trace_packet: Called with bytestream received/to be sent :param trace_pdu: Called with PDU received/to be sent :param trace_connect: Called when connected/disconnected .. tip:: The trace methods allow to modify the datastream/pdu ! Example:: from pymodbus.client import ModbusTcpClient async def run(): client = ModbusTcpClient("localhost") client.connect() ... client.close() Please refer to :ref:`Pymodbus internals` for advanced usage. """ def __init__( # pylint: disable=too-many-arguments self, host: str, *, framer: FramerType = FramerType.SOCKET, port: int = 502, name: str = "comm", source_address: tuple[str, int] | None = None, reconnect_delay: float = 0.1, reconnect_delay_max: float = 300, timeout: float = 3, retries: int = 3, trace_packet: Callable[[bool, bytes], bytes] | None = None, trace_pdu: Callable[[bool, ModbusPDU], ModbusPDU] | None = None, trace_connect: Callable[[bool], None] | None = None, ) -> None: """Initialize Modbus TCP Client.""" if not hasattr(self,"comm_params"): if framer not in [FramerType.SOCKET, FramerType.RTU, FramerType.ASCII]: raise TypeError("Only FramerType SOCKET/RTU/ASCII allowed.") self.comm_params = CommParams( comm_type=CommType.TCP, host=host, port=port, comm_name=name, source_address=source_address, reconnect_delay=reconnect_delay, reconnect_delay_max=reconnect_delay_max, timeout_connect=timeout, ) super().__init__( framer, retries, self.comm_params, trace_packet, trace_pdu, trace_connect, ) self.socket: socket.socket | None = None @property def connected(self) -> bool: """Check if socket exists.""" return self.socket is not None def connect(self): """Connect to the modbus tcp server.""" if self.socket: return True try: self.socket = socket.create_connection( (self.comm_params.host, self.comm_params.port), timeout=self.comm_params.timeout_connect, source_address=self.comm_params.source_address, ) Log.debug( "Connection to Modbus server established. Socket {}", self.socket.getsockname(), ) except OSError as msg: Log.error( "Connection to ({}, {}) failed: {}", self.comm_params.host, self.comm_params.port, msg, ) self.close() return self.socket is not None def close(self): """Close the underlying socket connection.""" if self.socket: self.socket.close() self.socket = None def send(self, request, addr: tuple | None = None): """Send data on the underlying socket.""" _ = addr if not self.socket: raise ConnectionException(str(self)) if request: return self.socket.send(request) return 0 def recv(self, size: int | None) -> bytes: """Read data from the underlying descriptor.""" if not self.socket: raise ConnectionException(str(self)) # socket.recv(size) waits until it gets some data from the host but # not necessarily the entire response that can be fragmented in # many packets. # To avoid split responses to be recognized as invalid # messages and to be discarded, loops socket.recv until full data # is received or timeout is expired. # If timeout expires returns the read data, also if its length is # less than the expected size. self.socket.setblocking(False) timeout = self.comm_params.timeout_connect or 0 # If size isn't specified read up to 4096 bytes at a time. if size is None: recv_size = 4096 else: recv_size = size data: list[bytes] = [] data_length = 0 time_ = time.time() end = time_ + timeout while recv_size > 0: try: ready = select.select([self.socket], [], [], end - time_) except ValueError: return self._handle_abrupt_socket_close(size, data, time.time() - time_) if ready[0]: try: if (recv_data := self.socket.recv(recv_size)) == b"": return self._handle_abrupt_socket_close( size, data, time.time() - time_ ) except SSLWantReadError: continue data.append(recv_data) data_length += len(recv_data) time_ = time.time() # If size isn't specified continue to read until timeout expires. if not size: break # Timeout is reduced also if some data has been received in order # to avoid infinite loops when there isn't an expected response # size and the slave sends noisy data continuously. if time_ > end: break recv_size = size - data_length self.last_frame_end = round(time.time(), 6) return b"".join(data) def _handle_abrupt_socket_close(self, size: int | None, data: list[bytes], duration: float) -> bytes: """Handle unexpected socket close by remote end. Intended to be invoked after determining that the remote end has unexpectedly closed the connection, to clean up and handle the situation appropriately. :param size: The number of bytes that was attempted to read :param data: The actual data returned :param duration: Duration from the read was first attempted until it was determined that the remote closed the socket :return: The more than zero bytes read from the remote end :raises ConnectionException: If the remote end didn't send any data at all before closing the connection. """ self.close() size_txt = size if size else "unbounded read" readsize = f"read of {size_txt} bytes" msg = ( f"{self}: Connection unexpectedly closed " f"{duration:.3f} seconds into {readsize}" ) if data: result = b"".join(data) Log.warning(" after returning {} bytes: {} ", len(result), result) return result msg += " without response from slave before it closed connection" raise ConnectionException(msg) def is_socket_open(self) -> bool: """Check if socket is open.""" return self.socket is not None def __repr__(self): """Return string representation.""" return ( f"<{self.__class__.__name__} at {hex(id(self))} socket={self.socket}, " f"ipaddr={self.comm_params.host}, port={self.comm_params.port}, timeout={self.comm_params.timeout_connect}>" )