Write from namedpipeclientstream to namedpipeserverstream accross WPF applications

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C#

threads

I have a program, that has to comunicate with another program that is called from the first.
I have managed to send the required data from the first to the second program using NamedPipes.
When the second program closes, i need to send some data back to the first program. I set up a NamedPipeServerStream in the first program and from the Closing event of the second program a NamedPipeClientStream. As far as i can tell the syncronization of the pipes dosen't work properly but i don't know why.

This is the code from the first program:

private const string CLIENTPROC = "C:\\Users\\Maik\\Source\\Repos\\PipeTest\\PipeClient\\obj\\x86\\Release\\PipeClient.exe";
private ManualResetEvent threadResetEvent;
private Thread threadHandlePipeSendLast;
private Process procClient;
private string msgPipeSend;
private volatile bool bMsgPipeSend;
public MainWindow()
{
    InitializeComponent();
    this.threadResetEvent = new ManualResetEvent(false);
    System.Diagnostics.Debug.WriteLine("### starting thread");
    this.threadHandlePipeSendLast = new Thread(new ThreadStart(this.ExchangeMapOverlayFileServer));
    this.threadHandlePipeSendLast.Start();
}

private void ExchangeMapOverlayFileServer()
{
    System.Diagnostics.Debug.WriteLine("server thread started");
    Thread.CurrentThread.Name = "apocalypse";
    try
    {
        using (NamedPipeServerStream namedPipeServer = new NamedPipeServerStream("ClosingPipe", PipeDirection.In, 1, PipeTransmissionMode.Byte))
        {
            string line;

            namedPipeServer.WaitForConnection();
            StreamReader sr = new StreamReader(namedPipeServer);
            Thread.Sleep(100);
            line = sr.ReadLine();
            handleRecvMsgFromPipe(line);
            namedPipeServer.Disconnect();
            namedPipeServer.Close();
        }
    }
    catch (Exception e)
    {
        System.Diagnostics.Debug.WriteLine("### " + e.Message + "\n" + e.StackTrace);
    }
}

private void handleRecvMsgFromPipe(string line)
{
    this.outbox.Text = line;
}

private void buttonOpenFormClient_Click(object sender, EventArgs e)
{
G


    if (this.procClient == null)
    {
        try
        {
            this.procClient = Process.Start(new ProcessStartInfo(CLIENTPROC));
        }
        catch (Exception exc)
        {
            MessageBox.Show(exc.Message, "Error");
        }
    }

}

this is the code from the second program

private ManualResetEvent threadResetEvent;
private Thread threadHandlePipeSendLast;

private string msgPipeSend;
private volatile bool bMsgPipeSend;
private bool done;

public MainWindow()
{
    InitializeComponent();
    this.threadResetEvent = new ManualResetEvent(false);
    this.Closing += (s, a) =>
    {
        System.Diagnostics.Debug.WriteLine("+++ FormClosing started.");
        this.threadHandlePipeSendLast = new Thread(new ThreadStart(this.HandleWindowClosing));
        this.threadHandlePipeSendLast.Start();
        while (!done)
        {
            Thread.Sleep(1000);
        }
    };
}

private void HandleWindowClosing()
{
    try
    {
        using (NamedPipeClientStream namedPipeClient = new NamedPipeClientStream(".", "ClosingPipe", PipeDirection.Out))
        {
            namedPipeClient.Connect();
            StreamWriter sw = new StreamWriter(namedPipeClient);
            //sw.AutoFlush = true;
            sw.WriteLine("last message");
            namedPipeClient.WaitForPipeDrain();
            namedPipeClient.Close();
            this.done = true;
        }

    }
    catch (Exception e) { System.Diagnostics.Debug.WriteLine(e.Message + "\n" + e.StackTrace); }
}

Where is my mistake?
Thank you.

What I have tried:

I tried:
- using WaitForPipeDrain() which is simply ignored/ dosen't do anything
- to manage the Threads with Sleep() at various points in the code
- to switch Server and Client
- Pipedirection.InOut on both ends
- Client with PipeDirection.Out, Server with PipeDirection.In (which is what i actually need)