RTU over TCP

[Ivica]

Hello everyone,

first of all, let me thank the author of this excellent module - it's great!

Secondly, I'm having some troubles making RTU over TCP packet. There is one example on groups here, but original poster found another solution. I was following that topic, but am stuck currently, with this code (I am python beginner)

from pymodbus import factory, transaction

from pymodbus.client import async

decoder = factory.ClientDecoder()

framer = transaction.ModbusRtuFramer(decoder)

client_protocol = async.ModbusClientProtocol(framer)

How can I send some read_holding_registers request with this? I have successfully read holding registers from a simulated device with 127.0.0.1 address using ModbusTcpClient. This real device in front of me is giving me troubles :)

Thank you in advance.

[Ivica]

Ideally, i would like to use sync client module, with support for RTU frames, as Albert Brandl suggested:

 If you prefer to use the sync client, you

could create a subclass of ModbusTcpClient and override its __init__

method. Try to replace
        BaseModbusClient.__init__(self, ModbusSocketFramer(ClientDecoder()))
with
        BaseModbusClient.__init__(self, ModbusRtuFramer(ClientDecoder()))

[Bashwork]

Since this is something that has been requested a few times now, I have added the ability to inject the framer of your choice into the synchronous clients (this ability is already available in the asynchronous versions)::

    client = ModbusTcpClient(host="1.1.1.1", framer=ModbusRtuFramer)

I have extensively tested this, so your mileage may vary.  This is contained in github commit: bdbcc512d6e284339f3861b7e63f51209cd40845

[Ivica]

I can't thank you enough for your work in general, but doing something like this is just insane! Thank you very much.

[Ivica]

Hello Bashwork,

I tried to implement your changes, and I'm getting some errors. Here is the code: http://pastebin.com/5NskRsFB with some comments about errors.

Am I doing something wrong? Software that came with the device communicates with it using the same settings.

[Ivica]

[Bashwork]

It seems that there is an error in the decoding step, could you enable the debug logging and copy what is logged to console; here is an example of doing this:

https://pymodbus.readthedocs.org/en/latest/examples/modbus-logging.html

[Ivica]

I will gladly report back to you, as soon as I get access to the device again, since it's only available to me once a week. And the holidays are starting...

Thank you for your interest in helping me.

[Ivica]

client=ModbusTCP(self.ip,self.port,framer=ModbusRtuFramer)

print client

client.connect()

print client.connect()

result = client read_holding_registers(7220,1)        

print result

10.23.1.175:502 #client

True #client.connect()

DEBUG:pymodbus.transaction:Running transaction 1 #logged to console

DEBUG:pymodbus.transaction:Transaction failed. (timed out) #logged to console

DEBUG:pymodbus.transaction:Transaction failed. (timed out) #logged to console

DEBUG:pymodbus.transaction:Transaction failed. (timed out) #logged to console

None #result

I've got this from my code. Did I turn the logging on properly? Were you expecting something like this on the output, or am I wrong?

[Michael401]

Hi,

I am also looking for a very basic example of using a rtu frame in tcp.

Here is my code (which does not work)

from pymodbus.client.sync import ModbusTcpClient as ModbusClient

from pymodbus.transaction import ModbusRtuFramer

client = ModbusClient(’localhost’, port=5020, framer=ModbusRtuFramer)

client.read_holding_registers(7,20,unit=1)

Ok, so first issue I have is that:

client = ModbusClient(’x.x.x.x', port=5020, framer=ModbusRtuFramer)

gives me this error

Exception AttributeError: "'ModbusTcpClient' object has no attribute 'socket'" in <bound method ModbusTcpClient.__del__ of <pymodbus.client.sync.ModbusTcpClient object at 0x7f0e54f9a250>> ignored Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: __init__() got an unexpected keyword argument 'framer'

If I do this instead

>>>client = ModbusClient()

>>> client.framer

<pymodbus.transaction.ModbusSocketFramer object at 0x2064610>

>>> client.framer = ModbusRtuFramer

>>> client.host = 'x.x.x.x'

>>> client.port = 20002

>>> client.connect()

True

Then I try reading a holding register

results = client.read_holding_registers(7,20,unit=1) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib/python2.7/dist-packages/pymodbus/client/common.py", line 109, in read_holding_registers return self.execute(request) File "/usr/local/lib/python2.7/dist-packages/pymodbus/client/sync.py", line 81, in execute return self.transaction.execute(request) File "/usr/local/lib/python2.7/dist-packages/pymodbus/transaction.py", line 70, in execute self.client._send(self.client.framer.buildPacket(request)) TypeError: unbound method buildPacket() must be called with ModbusRtuFramer instance as first argument (got ReadHoldingRegistersRequest instance instead)

The second issue is more pressing as I am sure that I am missing the point of using a non-default framer.

I was hoping that someone could publish a quick clear example of how to connect to an modbus server using RTU frame of TCP. For my project, I will be talking to a serial device on the other side of a microhard ipn3G modem va a tcp connection.

[Bashwork]

Here you go:

https://pymodbus.readthedocs.org/en/latest/examples/changing-framers.html

[Michael401]

Hey,

copied line for line I still get the error

>>> from pymodbus.client.sync import ModbusTcpClient as ModbusClient

>>> from pymodbus.transaction import ModbusRtuFramer as ModbusFramer

>>> client = ModbusClient('74.198.34.203', port=20002, framer=ModbusFramer)

Exception AttributeError: "'ModbusTcpClient' object has no attribute 'socket'" in <bound method ModbusTcpClient.__del__ of <pymodbus.client.sync.ModbusTcpClient object at 0x7ff0433a6c10>> ignored

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: __init__() got an unexpected keyword argument 'framer'

>>> 

I believe I have the latest version of pymodbus (i did a  pip install -U pymodbus just to be sure)

Any ideas?

Thanks!

Mike.

[Galen Collins]

Could you install from github instead of pip real quick, I don't think what is on pypi is the latest version.

Galen

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[Michael401]

Yep, I will give that a try and get back to you.

Thanks for the help!

Mike.

[Michael401]

Yep that worked.

Thanks!