Named pipes: C# server, C++ client

[Richard Andrew x64]

You might want to try Sysinternals' Process Explorer. It can enumerate every kernel object (that includes pipes) that exists inside a process. This way you could be sure the pipe name is being created the way you intend.

The difficult we do right away... ...the impossible takes slightly longer.

[Crazy Joe Devola]

thank you. I have Process Explorer but I don't know how to see list of objects for a process. I used the search option to search for "mypipe". It shows that the server has a handle to \Device\NamedPipe\pipe\mypipe . I tried to check the client to open "\\Device\\NamedPipe\\pipe\\mypipe" but that didn't help (I didn't expect it to work anyway).

[Crazy Joe Devola]

This is how the client opens the pipe:

hPipe=CreateFile("\\\\.\\pipe\\mypipe",
GENERIC_WRITE,//GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
0,
NULL) ;

if ( hPipe!=INVALID_HANDLE_VALUE)
{
return 0; //Success!!!
}

err = GetLastError();
if(err!=ERROR_PIPE_BUSY)
{
printf("Could not open pipe, GetLastError=%u\n", err);
return -1 ;
}

Create file returns an invalid handle. GetLastError() returns 2.

[Richard Andrew x64]

You do know that backslashes need to be escaped in C++, right? It should be:

hPipe=CreateFile("\\\\.\\pipe\\mypipe",
GENERIC_WRITE,//GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
0,
NULL) ;

The difficult we do right away... ...the impossible takes slightly longer.

[Crazy Joe Devola]

Yes i do :-) for some reason the codeproject shows just 1 backslash. I do have it like this:

"\\\\.\\pipe\\mypipe"

[Richard Andrew x64]

Let's see the code that creates the pipes in both projects.

The difficult we do right away... ...the impossible takes slightly longer.

[Crazy Joe Devola]

Server: C# NamedPipeServerStream pipeServer = new NamedPipeServerStream("\\\\.\\pipe\\mypipe", PipeDirection.In, 1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous); // Wait for a connection pipeServer.BeginWaitForConnection(new AsyncCallback(WaitForConnectionCallBack), pipeServer); Client: C++

	hPipe=CreateFile("\\\\\\\\\\\\\\\\.\\\\\\\\pipe\\\\\\\\mypipe", 
	                 GENERIC\_READ | GENERIC\_WRITE,
	                 0,
	                 NULL,
	                 OPEN\_EXISTING,
	                 0,
	                 NULL) ;
	if ( hPipe!=INVALID\_HANDLE\_VALUE) 
	{
		return 0; //Success!!!
	}

	err = GetLastError();
	if(err!=ERROR\_PIPE\_BUSY)
	{
		printf("Could not open pipe, GetLastError=%u\\n", err);
		return -1 ;
	}

	printf("Could not open pipe, GetLastError=%u. WaitNamedPipe.\\n", err);
	if(! WaitNamedPipe(pipe\_name,2000))
	{
		printf("Could not open pipe\\n");
		return -1 ;
	}

again: C++ client with C++ server - works. C# client with C# server - works. C++ client with C# server - does not works. Thank you.

[Richard Andrew x64]

This is just a guess, but could it be that since you have specified both GENERIC_READ and GENERIC_WRITE for the client, then you need to open the server as "InOut"?

The difficult we do right away... ...the impossible takes slightly longer.

[Crazy Joe Devola]

I thought of that. I tried changing the server side to InOut - it did not help. i also tried changing the client to GENERIC_WRITE without GENERIC_READ - it didn't work either. Thank you for all the advise, tips and time you spent trying to help - much appreciated.

[Crazy Joe Devola]

I think the problem was found.... On stackoverflow, someone posted this answer: C#'s NamedPipeClientStream, NamedPipeServerStream automatically append "\.\\pipe\" to the name I changed the C# code to open the pipe just as "mypipe" and now the connection is successful.

[Richard Andrew x64]

Glad you got it sorted. :)

The difficult we do right away... ...the impossible takes slightly longer.