Python script for Modbus RTU slave

Question

I want to make a script so that my controller acts as a Modbus RTU slave and reacts to request sent by another device.

The controller stores 10 booleans as 10 discrete inputs from address 1 to 10. They can only be read (fonction code 2).

As I understood, pymodbus can be used for this. My question is: is it how I'm supposed to set up a Modbus RTU slave? But because I get errors, do you know what I am doing wrong?

Here is the script that I'm trying to execute:

from pymodbus.datastore import ModbusSequentialDataBlock
from serial import Serial
import time
import sys
import random

# Create a serial port
serial = Serial(port='COM1',
                baudrate=9600,
                bytesize=8,
                parity='N',
                stopbits=1,
                timeout=0.5)

# Create a Modbus server context
store = ModbusSlaveContext(
    di=ModbusSequentialDataBlock.create(),
    co=ModbusSequentialDataBlock.create(),
    hr=ModbusSequentialDataBlock.create(),
    ir=ModbusSequentialDataBlock.create(),
    zero_mode=True
)

# Create a loop to change the discrete input from adress 1 to 10 every 2 seconds
while True:
    try:
        # Change the discrete input randomly
        for i in range(1, 11):
            store.setValues(1, i, [random.randint(0, 1)])
        time.sleep(2)
    except KeyboardInterrupt:
        server.stop()
        sys.exit()

My controller has a Windows OS and can execute python. It has a RS-232 port (DB9).

My testing set-up is a computer with QModMaster on it to try and read my discrete inputs.

Is it how a Modbus RTU slave should be set up?

I'm not sure what I'm doing wrong... The error message I get from QModMaster is just a time out error.