Inter-Process Communication between C# and C++ using named pipes

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Introduction

There might be some cases that you need to have two or more processes connected. One solution which I guess is more common is using sockets on local machine to connect process for interprocess communications. This is an example of interprocess communication using named pipes. The sample provides a code snippet for C# and C++ process communications.

Background

Named pipes are mainly used for inter-process communications. It can be one way or duplex communication between a pipe server and one or more pipe clients. Clients can have a stream which can be used to send/receive messages between processes. Name pipes has FIFO (First - In First - Out) behaviour.

Using the code

Two named pipes are created in this example. You have to run the C# application to initialise the pipes. Pipes are named myNamedPipe1 and myNamedPipe2, where in the C# application myNamedPipe1 is used for receiving and myNamedPipe2 for sending, and in C++ application myNamedPipe1 is used for sending and myNamedPipe2 for receiving.

A class called NamedPipeServer is used in C# code to create instances of namedpipes. Servers should be started after creating an instance of them and stopped when the application is closed. A Named pipe exists beyond the life of the process and must be deleted after the process is closed.

NamedPipeServer PServer1 = new NamedPipeServer(@"\\.\pipe\myNamedPipe1",0);
NamedPipeServer PServer2 = new NamedPipeServer(@"\\.\pipe\myNamedPipe2",1);
 
PServer1.Start();
PServer2.Start();
 
string Ms="Start";
do
{
   Console.WriteLine("Enter the message");
   Ms = Console.ReadLine();
   PServer2.SendMessage(Ms, PServer2.clientse);
} while (Ms != "quit");
 
PServer1.StopServer();
PServer2.StopServer();

This snipped keeps sending messages until it gets quit command, then it closes both named pipes.  Same name pipes with the exact same name are created in the C++ code and initialise.

LPTSTR lpszPipename1 = TEXT("\\\\.\\pipe\\myNamedPipe1"); 
LPTSTR lpszPipename2 = TEXT("\\\\.\\pipe\\myNamedPipe2");  

Same as C# code, a thread processes received messages, and a loop in the main thread sends messages to the other application.

do
{
    printf ("Enter your message: ");
    scanf ("%s",buf);  
    if(strcmp (buf,"quit") == 0)
        Write_St=FALSE;
    else
    {
        WriteFile(hPipe1, buf, dwBytesToWrite, &cbWritten, NULL);
        memset(buf,0xCC,100);
    }
}while(Write_St);

After running both applications you can send/receive messages between processes.