Not able to read and write holding registers directly from modbus server (pymodbus)

Question

I currently have a local modbus-TCP network on my computer, consisting of a modbus server and two modbus clients. I want it to be a network of one server and one client, but currently have not been able to write and read holding registers from my server hence the need for a redundant extra client.

My code is as follows, I have simplified it considerably for illustrative purposes

SERVER.PY

from pymodbus.server import StartTcpServer
from pymodbus.datastore import ModbusSparseDataBlock, ModbusSlaveContext, ModbusServerContext
from pymodbus.version import version
from pymodbus.device import ModbusDeviceIdentification

store = ModbusSlaveContext(hr=ModbusSparseDataBlock({0x00: [0]*0xff}))
context = ModbusServerContext(slaves=store, single=True)
identity = ModbusDeviceIdentification()
identity.VendorName = 'Pymodbus'
identity.ProductCode = 'PM'
identity.VendorUrl = 'http://github.com/bashwork/pymodbus/'
identity.ProductName = 'Pymodbus Server'
identity.ModelName = 'Pymodbus Server'
identity.MajorMinorRevision = version.short()

StartTcpServer(context=context, identity=identity, address=("0.0.0.0", 502))

CLIENT1.PY

from pymodbus.client import ModbusTcpClient

while True:
    client.write_registers(0, [power, current, energy]) # variables defined earlier
    feedback = client.read_registers(4, 3, unit=1)
    # operations now commence on feedback variable

CLIENT2.PY

import numpy as np
from pymodbus.client import ModbusTcpClient

while True:
    client.write_registers(4, [analytics, analytics2, analytics3]) # variables defined earlier
    system = client.read_registers(0, 3, unit=1)
    # operations now commence on system variable

I want the CLIENT2.PY to become the new server, i.e. something like the following

NEW_SERVER.PY

from pymodbus.server import StartTcpServer
from pymodbus.datastore import ModbusSparseDataBlock, ModbusSlaveContext, ModbusServerContext
from pymodbus.version import version
from pymodbus.device import ModbusDeviceIdentification

store = ModbusSlaveContext(hr=ModbusSparseDataBlock({0x00: [0]*0xff}))
context = ModbusServerContext(slaves=store, single=True)
identity = ModbusDeviceIdentification()
identity.VendorName = 'Pymodbus'
identity.ProductCode = 'PM'
identity.VendorUrl = 'http://github.com/bashwork/pymodbus/'
identity.ProductName = 'Pymodbus Server'
identity.ModelName = 'Pymodbus Server'
identity.MajorMinorRevision = version.short()

server = StartTcpServer(context=context, identity=identity, address=("0.0.0.0", 502))

while True:
    server.write_registers(4, [analytics, analytics2, analytics3]) # variables defined earlier
    system = server.read_registers(0, 3, unit=1)
    # operations now commence on system variable

CLIENT1.PY should remain the same as before in this example.

The issue is that I have not yet found a way to write to holding registers directly from the server, and instead have to create a client to do so, whilst the real server just sits there doing nothing but running. Help would be much appreciated

Not able to read and write holding registers directly from modbus server (pymodbus)

0 Answers0