IPC between C# and C++ using named pipes

Question

I have a C++ server application and C# client application, and I want them to communicate with each other using named pipes mechanism.

I want to use a multithreded server (each tread will service a client), I found a working code here: http://msdn.microsoft.com/en-us/library/windows/desktop/aa365588(v=vs.85).aspx

It works great with the C++ client from here: http://msdn.microsoft.com/en-us/library/windows/desktop/aa365592(v=vs.85).aspx

My goal is to make this C++ server to work with C# client, so I wrote this simple program for the client side:

public static void Main(string[] Args)
{
    //Client
    var client = new NamedPipeClientStream(".", "mynamedpipe", PipeDirection.InOut);
    client.Connect();

    StreamReader reader = new StreamReader(client, Encoding.Unicode);
    StreamWriter writer = new StreamWriter(client, Encoding.Unicode);
    int i = 0;
    while (true)
    {
        writer.WriteLine("Message" + i.ToString() + Char.MinValue);
        writer.Flush();
        i++;

        System.Console.WriteLine(reader.ReadLine());

        Console.ReadKey();
    }
}

The behavior I expect is :

Client->Server: "Message1"
Server->Client: "default answer from server"
Client->Server: "Message2"
Server->Client: "default answer from server"
Client->Server: "Message3"
Server->Client: "default answer from server"
Client->Server: "Message4"
Server->Client: "default answer from server"

And so on...

Instead, this is the output I get:

Pipe Server: Main thread awaiting client connection on \.\pipe\mynamedpipe Client connected, creating a processing thread.

Pipe Server: Main thread awaiting client connection on \.\pipe\mynamedpipe InstanceThread created, receiving and processing messages.

Client Request String:"????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????"

Client Request String:"Message0"

After some debugging here are few weird things I noticed:

1. client.Connect(); causes 2 bytes (not null terminated) to be written to the pipe. this explains the "?????..."
2. "Messege0" gets written correctly from the client side and the server reads it correctly also, but:
3. Client side does not seem to read the reply from the server ("default answer from server") correctly - it is stuck on the blocking "reader.ReadLine()" line. I do not think it is because of a bug on the server as the same server seems to work fine with the C++ client.

4. After closing the server, the message gets to the client. I added

   FlushFileBuffers(hPipe);

after

WriteFile()  

in the server - it did not help.

• Encoding seems to be correct on both sides - Unicode, Little Endien.

• Both server and client running on the same Windows machine.

The issue in item number 3, is the most disturbing to me, and I cannot find an explanation.