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I am trying to read and write data over Modbus TCP with python. When I am using ModbusPoll with the following setup everything works.

I try to read the data now with python and I am using the pymodbus library for this. My code looks like this:

from pymodbus.client.sync import ModbusTcpClient
from pymodbus.transaction import ModbusRtuFramer as ModbusFramer
client = ModbusTcpClient("192.168.0.7", port=502, framer=ModbusFramer)
success = client.connect()
read = client.read_holding_registers(address=4000)
read.registers
But I am always getting the following error:
ModbusIOException(InvalidMessageReceivedException('No response received, expected at least 2 bytes (0 received)'), 1)
This is what helped me.
Check slave_ID of your device (unit=slave_ID). It is not nessecary 1 or 0. In my case - 240, for example.
result = client.read_holding_registers(address=0x0010, count = 2, **unit=240**)
Documentation says:
    def write_register(self, address, value, **kwargs):
    :param address: The starting address to write to
    :param value: The value to write to the specified address
    **:param unit: The slave unit this request is targeting**
    :returns: A deferred response handle
    def read_holding_registers(self, address, count=1, **kwargs):
    :param address: The starting address to read from
    :param count: The number of registers to read
    **:param unit: The slave unit this request is targeting**
    :returns: A deferred response handle
Look file "common.py" or press Ctrl+B while cursor is on function.
        
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