NModbus Response error

[Jantje14M]

Hey,

I am trying to communicate with an array PLC through TCP. But when I want to read something I get the error:

"Response was not of expected transaction ID. Expected 4, received 0."

And when I'm trying to write something:

"Response slave address does not match request. Expected 1, reveived 0."

        TcpClient tcpClient = new TcpClient();

        private void btn_OpenPort_Click(object sender, EventArgs e)

        {

            try

            {

                tcpClient.Connect("192.168.2.35", 502);

                ModbusIpMaster master = ModbusIpMaster.CreateIp(tcpClient);

                

                master.Transport.Retries = 0;

                btn_OpenPort.Text = "Close Port";

                UpdateRTB(comPort.PortName.ToString() + " opened!");

            }

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

            }

        }

        // Read

        private void btn_Read_Click(object sender, EventArgs e)

        {

            // Read inputs

            try

            {

                byte slaveID = 1;           // PLC address

                ushort startAddress = 256;  // Starting address

                ushort numOfPoints = 1;     // Number of coils to read

                bool[] status = ModbusIpMaster.CreateIp(tcpClient).ReadCoils(slaveID, startAddress, numOfPoints);

                for (int i = 0; i < numOfPoints; i++)

                {

                    UpdateRTB(startAddress.ToString() + ": " + status[i]);

                    startAddress++;

                }

                // Output:  <input address>: True/False

            }

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message, "NModbus Error R1", MessageBoxButtons.OK, MessageBoxIcon.Error);

            }
        }

        // Write

        private void btn_Write_Click(object sender, EventArgs e)

        {

            // Write marker M

            try

            {

                byte slaveID = 1;           // PLC address

                ushort startAddress = 9728;  // Starting address

                bool value = false;     // value to write

                ModbusIpMaster.CreateIp(tcpClient).WriteSingleCoil(startAddress, value);

                UpdateRTB(startAddress.ToString() + ": " + value.ToString());

                // Output:  <output address>: True/False

            }

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message, "NModbus Error W1", MessageBoxButtons.OK, MessageBoxIcon.Error);

            }
        }

Before I did it with RTU and that worked fine.

I hope someone can catch my fault.

Greetings Jan

[Gavin Hill]

Hi Jan, did you ever find a solution to this problem?  I'm having a similar issue.

Gavin

[Umut Nuri KILIÇ]

Dear Gavin  and Jan,

I am facing same problem and while I am searching any solution for this problem at google, I found this topic. Have you found any solution? If you have, could you please share with me?

2 Haziran 2016 Perşembe 17:36:24 UTC+3 tarihinde Jantje14M yazdı:

[Gavin Hill]

Umut, I solved my issue by slowing the poll interval and increasing the timeout - it turns out I had a rather slow PLC.

Gavin Hill Director, Highpeak (Pty) Ltd. +27-83-601-8181 | ga...@highpeak.co.za | http://www.highpeak.co.za

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