Modbus.Net TcpClient fails exactly every 6th poll

Question

I implemented a Modbus.Net v1.4.3 client and poll data peridoically in a main program and experience strange behaviour.

Every 6th poll gives:

  Data = null
  Success = false
  ErrorCode = 0
  ErrorMsg  = ""

The other polls work just fine.

enter image description here

Feel free to blaim my code along the way.

In the following code only this line does the poll :

//Get data from machine
var result = await _machine.GetMachineMethods<IMachineMethodDatas>().GetDatasAsync(MachineDataType.CommunicationTag);`

Modbus Client class:

using Microsoft.Extensions.Logging;
using Modbus.Net;
using Modbus.Net.Modbus;

/// <summary>
/// Modbus using Modbus.Net
/// </summary>
internal class ModbusClient
{
    public ModbusClient(string ip, byte id, List<AddressUnit<int, int, int>> addressConfig)
    {
        // init machine object with address-unit config
        _machine = new ModbusMachine<int, int>(id, ModbusType.Tcp, ip, addressConfig, true, id, 0, 2);
    }

    /// <summary>
    /// Modbus.Net Machine
    /// </summary>
    private IMachineProperty<int> _machine;

    /// <summary>
    /// Poll configured addresses.
    /// </summary>
    /// <returns>Collection of <see cref="ReturnUnit{TReturn}"/></returns>
    /// <exception cref="IOException">Poll failed.</exception>
    public async Task<ICollection<ReturnUnit<double>>> PollReturnUnits()
    {
        //Get data from machine
        var result = await _machine.GetMachineMethods<IMachineMethodDatas>().GetDatasAsync(MachineDataType.CommunicationTag);

        //Error handling
        if (result.Datas is null || !result.IsSuccess)
        {
            throw new IOException($"code:{result.ErrorCode}, msg:{result.ErrorMsg}");
        }
        //Return AdressUnits
        return result.Datas.Values;
    }
}

Edit:

-Please don't rely on the documentation of the package, since it's outdated. Download package and paste my code to browse.

-The GetDatasAsync reads some configured registers. It returns a "ReturnStruct" with the properties (which partly have wrong plural): Datas, Success, ErrorMsg, ErrorCode.

Since we're encouraged to blaim your code: Data is plural, the term datas does not exist. — Palle Due
– Palle Due, Commented Jan 23 at 13:06
^^ Same goes for "informations", btw (from the guy that keeps on fixing that in the company code base since 2019) — Fildor
– Fildor, Commented Jan 23 at 13:18
Whatever it is, it's taking 5 seconds longer than the other "writes". Sounds like a "timeout" or "busy". When dealing with "devices", you need more awareness of "buffer" and "block" sizes (on the device); which can introduce "frames" into the processing cycle. — Gerry Schmitz
– Gerry Schmitz, Commented Jan 23 at 19:24
Consider testing with something like mbpoll or modpoll (both have adjustable poll rates) to see if these also fail in a similar way (thus establishing if the issue is your code/Modbus.Net, or the device itself). — Brits
– Brits, Commented Jan 24 at 4:06

stadla_ · Accepted Answer · 2025-01-25 11:33:37Z

0

I have tested the slave with this Modbus Scanner: https://store.chipkin.com/products/tools/cas-modbus-scanner

With an hour of observation I was able replicate the behaviour, altough it occours, that it's much less frequent with the scanner, which lead me to blame the modbus library first.

I guess thats it for this question. Thanks to everyone!

edited Jan 25 at 11:33

answered Jan 25 at 11:32

stadla_

14 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Modbus.Net TcpClient fails exactly every 6th poll

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related