Question

I am using CallNamedPipe() in VB6 to send messages to a C# named pipe server.
On the server side the pipe is created by:

new NamedPipeServerStream(pipeName, PipeDirection.InOut, numThreads);

On the client I use this call to write 2 bytes:

  Dim Header(1) As Byte
  Header(0) = 0
  Header(1) = 6
  res = CallNamedPipe(szPipeName, Header(0), 2, bArray(0), numBytes, cbRead, 3000)

The server saw the pipe connected because WaitForConnection() did return, but then could not read any bytes.
On the client side: CallNamedPipe failed and returned error code 87 (invalid parameters?)

My questions are:

1. Is the pipe created a byte mode or message mode type? MSDN says CallNamedPipe() fails if the pipe is byte mode.

2. Is there a way to write to a byte mode pipe in VB6. Do I have to change the server code to create a message mode pipe?

3. How to get my VB6 code working?

Answer 1

According to the documentation, the pipe is in byte mode when you use that constructor. I don’t know much about the non-.NET pipe calls, but I don’t see any reason why not to set the server to a message mode pipe if the VB6 needs it.