2

我需要在本机命名管道和 System.IO 命名管道之间发送多条消息。我从 All-In-One Code Framework（IPC 和 RPC）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 (Exception ex) { Console.WriteLine("服务器抛出错误：{0}", ex.Message); } 最后 { if (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;
            }
        }
    }

正如您在上面“从客户端向服务器发送请求”部分中的 for 循环中看到的那样，我试图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，然后它将去获取第二条消息。

4

2 回答 2

1

除了在一次写入中将其所有“消息”发送到管道之外，客户端无能为力。这是因为，在消息模式下，消息由发送方的写入调用完成分隔，并且您的服务器代码显式地只读取一条消息（在管道消息模式意义上）。请参阅CreateNamedPipe和ReadFile API文档：

数据作为消息流写入管道。管道将每个写入操作期间写入的字节视为一个消息单元。

如果在消息模式下读取命名管道并且下一条消息比 nNumberOfBytesToRead 参数指定的长，ReadFile 返回 FALSE，GetLastError 返回 ERROR_MORE_DATA。可以通过对 ReadFile 或 PeekNamedPipe 函数的后续调用来读取消息的其余部分。

处理多条消息的可能方法是：

  • 定义一些更高级别的框架协议，客户端可以通过该协议告诉服务器在每次消息交换中要读取多少条消息。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][frame trail:没有更多消息];
  • 一个多线程服务器，其中有一个专用线程不断地从客户端读取消息，其他操作（例如将消息写回客户端）在其他线程上完成；
于 2010-12-19T17:51:01.573 回答
0

谢谢你，克里斯，把我指向文档。我对你的答案投了赞成票，因为你引用的引文让我找到了我正在寻找的答案。

原来我只是被服务器代码的“接收来自客户端的请求”部分中的 do/while 循环弄糊涂了。也就是说，在我看来，它正在从客户端检索多条消息。但实际上，它是在检索单个消息的连续部分。我按如下方式更新了该代码部分。

// Receive a request from client.

string message = string.Empty;
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');
}
while (!finishRead);  // Repeat loop if ERROR_MORE_DATA

Console.WriteLine( "Message received from client: \"{0}\"", message );

至于在客户端对服务器的请求中划分多个“消息”，我可能只使用换行符。

于 2010-12-19T23:52:31.773 回答