writeBytes returning -1025 using LibNoDave

Question

I have a weird problem with my Connection from C# to my Simatic S7-1200. I am using LibNoDave to connect and i want to set bits of my SPS with the C#-program. This is working just fine but it only works 9 times and then the writeBytes(..) function returns -1025 and not 0 as it should and it is not setting the byte anymore. I then have to restart the application and it will work 9 times again.

This is my LibNoDave class.

static class LibNoDave
{

    static libnodave.daveConnection dc;
    static bool connection = false;

    public static bool CreateConnection()
    {
        const string IP = "192.168.1.250";
        const int Rack = 0;
        const int Slot = 0;
        libnodave.daveOSserialType fds;
        libnodave.daveInterface di;

        try
        {
            fds.rfd = libnodave.openSocket(102, IP);
            fds.wfd = fds.rfd;

            if (fds.rfd > 0)
            {
                di = new libnodave.daveInterface(fds, "IF1",
                              0, libnodave.daveProtoISOTCP,
                              libnodave.daveSpeed187k);

                di.setTimeout(1000000);
                int res = di.initAdapter();
                if (res == 0)
                {

                    dc = new libnodave.daveConnection(di, 0,
                                                       Rack, Slot);
                    res = dc.connectPLC();
                    if (res == 0)
                    {
                        connection = true;
                        return true;
                    }
             }
        }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

        return false;
    }


    public static void DisconnectPLC()
    {
        if (connection)
        {
            dc.disconnectPLC();
            libnodave.closeSocket(102);
            connection = false;
        }

    }

    public static void WritePLC(int anfangswert, byte wert)
    {
        if (connection)
        {
            byte[] buf = new Byte[1];
            buf[0] = wert;
            int res = dc.writeBytes(libnodave.daveFlags, 0, anfangswert, 1, buf);
            MessageBox.Show(res.ToString());
        }

    }
}

Here I am calling the functions:

private void frmAuslagerung_Load(object sender, EventArgs e)
    {
        if (!LibNoDave.CreateConnection())
        {
            finished = true;
            this.Close();
        }

        LibNoDave.WritePLC(1, Byte.Parse(auto.Position.Lade.ToString()));

    }

    private void frmAuslagerung_FormClosing(object sender, FormClosingEventArgs e)
    {
        if (!finished)
        {
            //e.Cancel = true; //Not in code for testing
            LibNoDave.DisconnectPLC(); //Only for testing
        }            
        else
            LibNoDave.DisconnectPLC();
    }

Answer 1

It's old, but for others to find: in my case it was the declaration of fds and di: they had to be class members and not local to the connect method, or the timeout value was being lost later on.

Answer 2

it can be problem closing the connection try with:

    public static void DisconnectPLC()
    {
        if (connection)
        {
          dc.disconnectPLC();
          di.disconnectAdapter();
          libnodave.closePort(fds.rfd);
          connection = false;
         }
}

Answer 3

I don´t see any problem in code and I don´t know neither your device nor LibNoDave, but the problem may be related to:

1- Is some receiver an "One single digit" (like 0 to 9) address or container ?

2- The position is being truly reseted as I see in WritePLC function?

3- The "LibNoDave.WritePLC" is incrementing its pointer?

Good luck.