Named Pipes between C# and Python

Question

I'm trying to create a two-way communication channel between two programs (one in Python and another in C#)

When I create a named pipe between two C# programs or two Python programs, everything is OK, but when I try to (for example) connect to the C# server from Python code, it does not work:

C# code:

NamedPipeServerStream server = new NamedPipeServerStream(
    "Demo", PipeDirection.InOut, 100, PipeTransmissionMode.Byte,
    PipeOptions.None, 4096, 4096)

If I use win32pipe in Python, code blocks on ConnectNamedPipe (it never returns)

p = win32pipe.CreateNamedPipe(
    r'\\.\pipe\Demo',
    win32pipe.PIPE_ACCESS_DUPLEX,
    win32pipe.PIPE_TYPE_BYTE | win32pipe.PIPE_WAIT,
    1, 65536, 65536,
    300,
    None)
win32pipe.ConnectNamedPipe(p)

If I use open function, it just establishes a connection, but nothing occurs:

open( '\\\\.\\pipe\\Demo', 'r+b' )

Now if I close the Python program, C# server receives just one data item from Python and a System.IO.IOException raises with "Pipe is broken" message

Am I doing anything wrong ?

Answer 1

According to MS, ConnectNamedPipe is the "server-side function for accepting a connnection". That's why it never returns - it's waiting for a connection from a client. Here's some sample code showing C# as the server and python as the client:

C#:

NamedPipeServerStream server = new NamedPipeServerStream("Demo");
server.WaitForConnection();

MemoryStream stream = new MemoryStream();
using (BinaryWriter writer = new BinaryWriter(stream))
{
    writer.Write("print \"hello\"");
    server.Write(stream.ToArray(), 0, stream.ToArray().Length);
}

stream.Close();
server.Disconnect();
server.Close();

python:

import win32file
fileHandle = win32file.CreateFile("\\\\.\\pipe\\Demo", win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0, None, win32file.OPEN_EXISTING, 0, None)
left, data = win32file.ReadFile(fileHandle, 4096)
print data # prints \rprint "hello"

Answer 2

OK, I fixed the problem. I should seek to position 0 of buffer.

My Python code:

    win32file.WriteFile(CLIENT_PIPE,"%d\r\n"%i ,None)
    win32file.FlushFileBuffers(CLIENT_PIPE)
    win32file.SetFilePointer(CLIENT_PIPE,0,win32file.FILE_BEGIN)
    i,s = win32file.ReadFile(CLIENT_PIPE,10,None)

Answer 3

I think you are meant to use win32pipe.popen, not open.

Also try: pipe.flush(), pipe.read(), and time.sleep(0.01). Sometimes IPC takes a while to sync up.

I don't really know, that's my experience with the subprocess pipes. win32pipe might be different.