c# - 在 native 命名管道和 System.IO 命名管道之间发送多条消息

Question

我需要在 native 命名管道和 System.IO 命名管道之间发送多条消息。我从 All-In-One Code Framework(IPC 和 RPC)中获得了这种通信两端的代码。

服务器:

SafePipeHandle hNamedPipe = null;

try { SECURITY_ATTRIBUTES sa = null;
sa = CreateNativePipeSecurity();

// Create the named pipe.
hNamedPipe = NativeMethod.CreateNamedPipe(
    Constants.FullPipeName,             // The unique pipe name.
    PipeOpenMode.PIPE_ACCESS_DUPLEX,    // The pipe is duplex
    PipeMode.PIPE_TYPE_MESSAGE |        // Message type pipe 
    PipeMode.PIPE_READMODE_MESSAGE |    // Message-read mode 
    PipeMode.PIPE_WAIT,                 // Blocking mode is on
    PIPE_UNLIMITED_INSTANCES,           // Max server instances
    1024,                 // Output buffer size
    1024,                 // Input buffer size
    NMPWAIT_USE_DEFAULT_WAIT,           // Time-out interval
    sa                                  // Pipe security attributes
);

if (hNamedPipe.IsInvalid)
{
    throw new Win32Exception();
}

Console.WriteLine("The named pipe ({0}) is created.", Constants.FullPipeName);

// Wait for the client to connect.
Console.WriteLine("Waiting for the client's connection...");
if (!NativeMethod.ConnectNamedPipe(hNamedPipe, IntPtr.Zero))
{
    if (Marshal.GetLastWin32Error() != ERROR_PIPE_CONNECTED)
    {
        throw new Win32Exception();
    }
}
Console.WriteLine("Client is connected.");

// 
// Receive a request from client.
// 

string message;
bool finishRead = false;
do
{
    byte[] bRequest = new byte[1024];
    int cbRequest = bRequest.Length, cbRead;

    finishRead = NativeMethod.ReadFile(
        hNamedPipe,             // Handle of the pipe
        bRequest,               // Buffer to receive data
        cbRequest,              // Size of buffer in bytes
        out cbRead,             // Number of bytes read 
        IntPtr.Zero             // Not overlapped 
        );

    if (!finishRead &&
        Marshal.GetLastWin32Error() != ERROR_MORE_DATA)
    {
        throw new Win32Exception();
    }

    // Unicode-encode the received byte array and trim all the 
    // '\0' characters at the end.
    message = Encoding.Unicode.GetString(bRequest).TrimEnd('\0');
    Console.WriteLine("Receive {0} bytes from client: \"{1}\"", cbRead, message);
}
while (!finishRead);  // Repeat loop if ERROR_MORE_DATA

// 
// Send a response from server to client.
// 

message = "Goodbye\0";
byte[] bResponse = Encoding.Unicode.GetBytes(message);
int cbResponse = bResponse.Length, cbWritten;

if (!NativeMethod.WriteFile(
    hNamedPipe,                 // Handle of the pipe
    bResponse,                  // Message to be written
    cbResponse,                 // Number of bytes to write
    out cbWritten,              // Number of bytes written
    IntPtr.Zero                 // Not overlapped
    ))
{
    throw new Win32Exception();
}

Console.WriteLine("Send {0} bytes to client: \"{1}\"",
    cbWritten, message.TrimEnd('\0'));

// Flush the pipe to allow the client to read the pipe's contents 
// before disconnecting. Then disconnect the client's connection.
NativeMethod.FlushFileBuffers(hNamedPipe);
NativeMethod.DisconnectNamedPipe(hNamedPipe); 

} catch (异常前){ Console.WriteLine("服务器抛出错误:{0}", ex.Message);}最后{ 如果 (hNamedPipe != null) { hNamedPipe.Close(); hNamedPipe = null; }

客户:

            NamedPipeClientStream pipeClient = null;

        try
        {
            // Try to open the named pipe identified by the pipe name.

            pipeClient = new NamedPipeClientStream(
                ".",         // The server name
                Constants.PipeName,           // The unique pipe name
                PipeDirection.InOut,        // The pipe is duplex
                PipeOptions.None            // No additional parameters
            );

            pipeClient.Connect(5000);
            MessageBox.Show(
                string.Format( "The named pipe ({0}) is connected.", Constants.PipeName )
            );

            pipeClient.ReadMode = PipeTransmissionMode.Message;

            // 
            // Send a request from client to server
            // 

            for ( int i = 0; i < 2; i++ ) {

                string message = "hello my pipe dream\0";
                byte[] bRequest = Encoding.Unicode.GetBytes( message );
                int cbRequest = bRequest.Length;

                pipeClient.Write( bRequest, 0, cbRequest );

                MessageBox.Show(
                    string.Format( "Send {0} bytes to server: \"{1}\"", cbRequest, message.TrimEnd( '\0' ) )
                );
            }

            //
            // Receive a response from server.
            // 

            do
            {
                byte[] bResponse = new byte[1024];
                int cbResponse = bResponse.Length, cbRead;

                cbRead = pipeClient.Read(bResponse, 0, cbResponse);

                // Unicode-encode the received byte array and trim all the 
                // '\0' characters at the end.
                string message = Encoding.Unicode.GetString(bResponse).TrimEnd('\0');
                Console.WriteLine("Receive {0} bytes from server: \"{1}\"",
                    cbRead, message);
            }
            while (!pipeClient.IsMessageComplete);

        }
        catch (Exception ex)
        {
            new ErrorDialog( ex ).ShowDialog();
        }
        finally
        {
            // Close the pipe.
            if (pipeClient != null)
            {
                pipeClient.Close();
                pipeClient = null;
            }
        }
    }

正如您从上面“从客户端向服务器发送请求”部分的 for 循环中看到的那样，我正在尝试弄清楚如何向服务器发送多条消息。我看到服务器代码循环执行，直到 NativeMethod.ReadFile() 方法返回 true。我的问题是它总是在读取第一条消息后返回 true，而忽略第二条消息 所以我的问题，具体来说，是我需要在客户端代码中做什么，以便此方法返回 false，然后它就会去获取第二条消息。

Answer 1

客户端除了将其所有“消息”一次写入管道外，无能为力。这是因为，在消息模式下，消息由发送方完成的写调用分隔，并且您的服务器代码明确地只读取一条消息(在管道消息模式意义上)。参见 CreateNamedPipe和 ReadFile API文档:

Data is written to the pipe as a stream of messages. The pipe treats the bytes written during each write operation as a message unit.

If a named pipe is being read in message mode and the next message is longer than the nNumberOfBytesToRead parameter specifies, ReadFile returns FALSE and GetLastError returns ERROR_MORE_DATA. The remainder of the message can be read by a subsequent call to the ReadFile or PeekNamedPipefunction.

处理多条消息的可能方法是:

• 定义一些更高级别的框架客户端可以告诉的协议(protocol)服务器要读取多少条消息在每个消息交换中。然后，客户端将发送一系列消息，例如 [framing header:count=3][message 1][message 2][message 3]，或者 [message 1][message 2][message 3][framing trailer:没有更多消息];
• 一个多线程服务器，其中有是连续的专用线程读取来自客户端的消息，其他操作，如写作消息返回给客户端在其他线程上完成；