CODEWITHSUNDEEP
c#named-pipes
pinebitter
pinebitter

Reputation: 100

Named pipes are failing when clients does nothing but quickly connect-disconnect

I'm building an application that uses Named Pipes for IPC. When started writing a stress test, I found an issue related to when a client does quickly connect-disconnect.

Server code:

static void ServerThread()
{
    var serverPipe = new NamedPipeServerStream("myipc", PipeDirection.InOut, -1, PipeTransmissionMode.Message, PipeOptions.Asynchronous | PipeOptions.WriteThrough);

    serverPipe.BeginWaitForConnection(
        ar =>
        {
            var thisPipe = (NamedPipeServerStream)ar.AsyncState;
            thisPipe.EndWaitForConnection(ar);

            Task.Factory.StartNew(ServerThread);

            thisPipe.Dispose();
        },
       serverPipe);
}

Client does nothing but connect-disconnect as follow:

static void RunClients()
{
    for (int i = 0; i < 100; i++)
    {
        var clientPipe = new NamedPipeClientStream(".", "myipc", PipeDirection.InOut, PipeOptions.Asynchronous | PipeOptions.WriteThrough);

        clientPipe.Connect(1000);
        clientPipe.Dispose();
    }
}

When this runs, one of the clients is failing in Connect() while the server fails in BeginWaitForConnection - saying Pipe is being closed. If I add at least Thread.Sleep(100) before each client disposes - everything works just fine. I'm sure what I'm doing is a corner case, but I believe the pipes should be able to handle this in greaceful way.

Any ideas on what could be wrong?

Thanks!

Upvotes: 1

Views: 1594

Answers (1)

Hans Passant
Hans Passant

Reputation: 941635

one of the clients is failing in Connect()

Because the server immediately disposes the pipe after connecting.

the server fails in BeginWaitForConnection

Because the client immediately disposes the pipe after connecting.

I believe the pipes should be able to handle this in greaceful way.

It does, it gracefully throws an exception to let your code know that something exceptional happened. You seem to assume it is normal that code closes a pipe without doing anything to let the other end know that the pipe is about to disappear. That is not normal, it is exceptional. So you get an exceptional notification for it.

You catch exceptions with try/catch. There are two things you can do in your catch handler. You can assume that it is okay for code to close a pipe willy-nilly, in which case you do nothing beyond closing your end of the pipe and get out. Or you can assume that something Really Bad happened because the other end of the pipe didn't say goodbye nicely. Which is rather important to distinguish the oh-crap kind of mishaps, like a pipe client or the server crashing. It is up to you to choose your preferred way, but I strongly recommend to not ignore the oh-crap scenarios, it does and will happen. You just created a good simulation of such a mishap.

Upvotes: 2

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