C＃C ++命名管道连接

Question

I am trying to connect ac# project with a c++ project using named pipes but the c++ project doesn't connect.

ps: the .exe are both in the same file

side question: i don't understand the use of "\\\\.\\pipe\\" before my pipe name. what does it do and it is really necesarry?

Here's the my code maybe you can spot the error

C# server:

Program.cs

static class Program
{

    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        pipeHandler pipe = new pipeHandler();

        var proc = new Process();
        proc.StartInfo.FileName = "cplpltestpipes.exe";
        proc.Start();


        pipe.establishConnection();

        Application.Run(new Form1(pipe));
    }
}


public class pipeHandler
{

    private StreamReader re;
    private StreamWriter wr;
    private NamedPipeServerStream pipeServer;

    public void establishConnection()
    {
       pipeServer = new NamedPipeServerStream("myNamedPipe1");
        pipeServer.WaitForConnection();
        re = new StreamReader(pipeServer);
        wr = new StreamWriter(pipeServer);
    }

    public void writePipe(string text)
    {
        wr.Write(text);

    }

    public string readPipe()
    {
        if(re.Peek()==-1)
            System.Threading.Thread.Sleep(2000);
        if (re.Peek() > -1)
        {
            string s;
            s = re.ReadToEnd();
            return s;
        }
        else
            return "fail";
    }


}

Form1.cs:

public partial class Form1 : Form
{
    pipeHandler pipePointer;
    public Form1(pipeHandler pipe)
    {
        pipePointer=pipe;
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void button1_Click(object sender, EventArgs e)
    {
        pipePointer.writePipe(textBox1.Text);
        textBox2.Text = pipePointer.readPipe();
    }


}

c++ client

#define chrSize 16

int main()
{
    TCHAR chr[chrSize];
    DWORD bytesRead;



HANDLE pipeHandler;
LPTSTR pipeName = TEXT("\\\\.\\pipe\\myNamedPipe1");


pipeHandler = CreateFile(
    pipeName,   // pipe name 
    GENERIC_READ |  // read and write access 
    GENERIC_WRITE,
    0,              // no sharing 
    NULL,           // default security attributes
    OPEN_EXISTING,  // opens existing pipe 
    0,              // default attributes 
    NULL);          // no template file 

bool flag=false;

while (!flag) 
{
    flag = ConnectNamedPipe(pipeHandler, NULL);
    cout << "trying";
}



ReadFile(
    pipeHandler,    // pipe handle 
    chr,    // buffer to receive reply 
    chrSize * sizeof(TCHAR),  // size of buffer 
    &bytesRead,  // number of bytes read 
    NULL);    // not overlapped 

cout << chr;


LPTSTR pipeMessage = TEXT("message receive");
DWORD bytesToWrite= (lstrlen(pipeMessage) + 1) * sizeof(TCHAR);
DWORD cbWritten;


WriteFile(
    pipeHandler,                  // pipe handle 
    pipeMessage,             // message 
    bytesToWrite,              // message length 
    &cbWritten,             // bytes written 
    NULL);                  // not overlapped 


CloseHandle(pipeHandler);

}

Running the program just gives this exception in C#

************** Exception Text ************** System.InvalidOperationException: Pipe hasn't been connected yet. .... .... ....

and in c++ just keeps printing "trying" in console

Answer 1

When you call CreateFile how does CreateFile know that the object represented by the string myNamedPipe1 is a pipe? It knows because the name was prefixed with \\\\ServerName\\pipe\\ .

In your case ServerName can just be . because that is a shortcut for "This machine", if you switch your code to LPTSTR pipeName = TEXT("\\\\\\\\.\\\\pipe\\\\myNamedPipe1"); it should start working if there are no other issues.

you don't need to put it there in the C# code because the NamedPipeServerStream class puts it there for you .

EDIT: Looking over your code, you may want to move pipeServer = new NamedPipeServerStream("myNamedPipe1"); to the constructor of pipeHandler , right now your C++ program may start up before the server is ever started, even if you had the correct name you still might get the error.

EDIT2: ConnectNamedPipe is the C++ equivalent of pipeServer.WaitForConnection(); , you should not be doing that if the C++ program is the client. You should be good to go reading and writing as soon as you have a valid handle from CreateFile

EDIT3: here is a example of how to rewrite the C# app to start the server up before starting the C++ app

static class Program
{    
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        //The server now gets created here.
        pipeHandler pipe = new pipeHandler();    

        var proc = new Process();
        proc.StartInfo.FileName = "cplpltestpipes.exe";
        proc.Start();

        //The server used to be created here.
        pipe.EstablishConnection();

        Application.Run(new Form1(pipe));
    }
}


public class pipeHandler
{    
    private StreamReader re;
    private StreamWriter wr;
    private NamedPipeServerStream pipeServer;

    public pipeHandler()
    {
       //We now create the server in the constructor.
       pipeServer = new NamedPipeServerStream("myNamedPipe1");
    }

    public void establishConnection()
    {
        pipeServer.WaitForConnection();
        re = new StreamReader(pipeServer);
        wr = new StreamWriter(pipeServer);
    }
 ...
}

Then in your C++ code delete

while (!flag) 
{
    flag = ConnectNamedPipe(pipeHandler, NULL);
    cout << "trying";
}