Issue on async TCP client auto-reconnect

[alexis-care]

Hey everyone!

First of all, thank you for the package and the work! It helps me a lot in my daily work ^^.

Context:
version: 3.8.0

Use case:
I'm trying to use the auto-reconnect feature of the AsyncModbusTcpClient class.
However, I'm facing issues when the connection is dropped, without an EOF sent by the server.

When reconnecting, an asyncio CancelledError is raised in the TransactionManager class. The canceled future causes this error.

Workaround
I find a workaround to avoid the issue. You just need to re-instantiate the future in a reconnect callback.

I don't know if I handled my use case wrong; this is an issue with the package. Any idea?
I have included a small example of the issue below.

Small example:

import asyncio
from pymodbus.client import AsyncModbusTcpClient
from pymodbus.exceptions import ModbusIOException, ConnectionException

client = None

# The Workaround
def connect_callback(connection_status: bool):
    global client
    if connection_status:
        client.ctx.response_future = asyncio.Future()


async def task_get_value():
    global client
    i = 0
    print("create task")
    try:
        print(f"Loop {i}")
        try:
            while True:
                await client.read_input_registers(100, count=1)
                await asyncio.sleep(1)

        except (ModbusIOException, ConnectionException) as PybusException:
            print("PybusException")
        await asyncio.sleep(1)
        i += 1
    except asyncio.exceptions.CancelledError:
        print("asyncio CancelledError")


async def main():
    global client
    client = AsyncModbusTcpClient(
        name="device",
        host=IP,
        port=1234,
        reconnect_delay=5,
        reconnect_delay_max=5,
        # trace_connect=connect_callback,
        retries=0,
    )
    await client.connect()

    task = asyncio.create_task(task_get_value())

    while True:
        if task.done() and client.connected:
            task = asyncio.create_task(task_get_value())

        await asyncio.sleep(1)


if __name__ == "__main__":
    asyncio.run(main())

Thank's in advance !

[janiversen]

your code looks ok, since you have made a workaround then please submit a pull request, so we can review it, and other users can benefit from it.