Named Pipes between C# and Python

pipe_client.py

import time
import struct

f = open(r'\\.\pipe\NPtest', 'r+b', 0)
i = 1

while True:
    s = 'Message[{0}]'.format(i).encode('ascii')
    i += 1
        
    f.write(struct.pack('I', len(s)) + s)   # Write str length and str
    f.seek(0)                               # EDIT: This is also necessary
    print('Wrote:', s)

    n = struct.unpack('I', f.read(4))[0]    # Read str length
    s = f.read(n).decode('ascii')           # Read str
    f.seek(0)                               # Important!!!
    print('Read:', s)

    time.sleep(2)

pipe_server.cs

void run_server()
{
    // Open the named pipe.
    var server = new NamedPipeServerStream("NPtest");

    Console.WriteLine("Waiting for connection...");
    server.WaitForConnection();

    Console.WriteLine("Connected.");
    var br = new BinaryReader(server);
    var bw = new BinaryWriter(server);

    while (true) {
        try {
            var len = (int) br.ReadUInt32();            // Read string length
            var str = new string(br.ReadChars(len));    // Read string

            Console.WriteLine("Read: \"{0}\"", str);

            str = new string(str.Reverse().ToArray());  // Just for fun

            var buf = Encoding.ASCII.GetBytes(str);     // Get ASCII byte array     
            bw.Write((uint) buf.Length);                // Write string length
            bw.Write(buf);                              // Write string
            Console.WriteLine("Wrote: \"{0}\"", str);
        }
        catch (EndOfStreamException) {
            break;                    // When client disconnects
        }
    }

    Console.WriteLine("Client disconnected.");
    server.Close();
    server.Dispose();
}

Almost 9 years old but still fantastic! Very nearly works straight away. The only major change I remember making is line 11 of the .py file.

f.write(struct.pack('I', len(s)) + s)   # Write str length and str

Python produces error when concatenating string and byte types. Should be changed to:

f.write(struct.pack('I', len(s)) + str.encode(s))  # Write str length and str

Hi @dchc123. I edited your comment to add code formatting, making it much easier to read.

My original gist was written for Python 2. I updated it for Python 3 (but didn't test it since I rarely use Windows now):

• Use print() function syntax
• Call .encode('ascii') on message to be sent and .decode('ascii') on the received message
  • I prefer an explicit encoding rather than the default encoding which is used by your suggestion of (str.encode(s)). The default encoding is often UTF-8. Since the C# side used ASCII, it should be the same on both sides.