CODEWITHSUNDEEP
modbuspymodbus
Mr. Fegur
Mr. Fegur

Reputation: 797

How to find out if a client is connected to a pymodbus tcp server

I have a pymodbus server running and I'd like to know if a client is connected to it that it is serving. Is there any way to do that? I can't see an obvious way.

I'm using the synchronous server:

pymodbus.server.sync.ModbusTcpServer

Upvotes: 3

Views: 1574

Answers (1)

Tomer Simhony
Tomer Simhony

Reputation: 1

I'm not sure how to have a server publish its state in a publisher/subscriber pattern, but one way to ascertain whether a server is running is to poll it with a client. As was mentioned in the comments, setting up a logger from the logging module can also be useful.

The AsyncModbusTcpClient class has a connected attribute which is a bool value you can check. A True value indicates that the server is running. Here I've wrapped the client in a class to demonstrate that you can add any logic you care to to the boolean check.

from pymodbus.client import AsyncModbusTcpClient

class PymodbusAsyncClient():
    def __init__(self, host, port=502):
        self.host = host
        self.port = port
        self.client = AsyncModbusTcpClient(self.host, port=self.port)

    async def connect(self) -> None:
        await self.client.connect()
        if self.client.connected:
            print(f"Connected to Modbus server at {self.host}:{self.port}")
            return True

        return False`

# Server logging
logging.basicConfig(
    filename="path/to/logfile/pymodbus_server.log",
    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
    level=logging.INFO,
)

# Run server
await StartAsyncTcpServer(context, identity=identity, address=("localhost", 502))

logging output:

2024-05-30 17:18:21,394 - pymodbus.logging - INFO - Server listening.

2024-05-30 17:18:30,370 - root -INFO - Connected to Modbus server at localhost:502`

Upvotes: 0

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