多个管道服务器实例的异步 NamedPipes

Posted 2023-02-16

【中文标题】多个管道服务器实例的异步 NamedPipes

【英文标题】：Async NamedPipes in case of multiple pipe server instances

【发布时间】：2014-07-11 15:32:57

【问题描述】：

我正在使用来自 this article 的代码，唯一的区别是 ma​​xNumberOfServerInstances 设置为 -1（具有相同管道名称的服务器实例的数量仅受系统资源）在 NamedPipeServerStream 构造函数

异步监听方法【监听服务器类】：

class PipeServer

string _pipeName;

public void Listen(string PipeName)

    try
    
        // Set to class level var so we can re-use in the async callback method
        _pipeName = PipeName;
        // Create the new async pipe 
        NamedPipeServerStream pipeServer = new NamedPipeServerStream(PipeName, 
           PipeDirection.In, -1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous);

        // Wait for a connection
        pipeServer.BeginWaitForConnection
        (new AsyncCallback(WaitForConnectionCallBack), pipeServer);
    
    catch (Exception oEX)
       ...   


private void WaitForConnectionCallBack(IAsyncResult iar)

    try
    
        // Get the pipe
        NamedPipeServerStream pipeServer = (NamedPipeServerStream)iar.AsyncState;
        // End waiting for the connection
        pipeServer.EndWaitForConnection(iar);

        // Read the incoming message
        byte[] buffer = new byte[255];           
        pipeServer.Read(buffer, 0, 255);

        // Convert byte buffer to string
        string stringData = Encoding.UTF8.GetString(buffer, 0, buffer.Length);
        ...

        // Kill original sever and create new wait server
        pipeServer.Close();
        pipeServer = null;
        pipeServer = new NamedPipeServerStream(_pipeName, PipeDirection.In, 
           -1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous);

        // Recursively wait for the connection again and again....
        pipeServer.BeginWaitForConnection(
           new AsyncCallback(WaitForConnectionCallBack), pipeServer);
    
    catch
     ... 

异步发送方法 [PipeClient 类]

class PipeClient

public void Send(string SendStr, string PipeName, int TimeOut = 1000)

    try
    
        NamedPipeClientStream pipeStream = new NamedPipeClientStream
           (".", PipeName, PipeDirection.Out, PipeOptions.Asynchronous);

        // The connect function will indefinitely wait for the pipe to become available
        // If that is not acceptable specify a maximum waiting time (in ms)
        pipeStream.Connect(TimeOut);            

        byte[] _buffer = Encoding.UTF8.GetBytes(SendStr);
        pipeStream.BeginWrite
        (_buffer, 0, _buffer.Length, new AsyncCallback(AsyncSend), pipeStream);
    
    catch (TimeoutException oEX)
        ...        


private void AsyncSend(IAsyncResult iar)

    try
    
        // Get the pipe
        NamedPipeClientStream pipeStream = (NamedPipeClientStream)iar.AsyncState;

        // End the write
        pipeStream.EndWrite(iar);
        pipeStream.Flush();
        pipeStream.Close();
        pipeStream.Dispose();
    
    catch (Exception oEX)
        ...         

我有两个 WinForms 应用程序：服务器只有 Listen 按钮（点击结果在 Listen 方法调用中），客户端有 textBox 用于文本输入和 发送 按钮（点击结果在 Send 方法调用中）。

我执行以下操作：

启动服务器应用程序的多个副本（结果 - 创建多个具有相同管道名称的 NamedPipeServerStream 实例） 点击每个按钮中的收听按钮 启动客户端应用程序 点击发送按钮

这导致只有一个服务器应用程序（那个，其侦听按钮首先被点击）接收消息。如果我再次单击 Send 按钮 - 第二次单击的服务器应用程序会收到消息。因此，实例按其上的 Listen 按钮的顺序接收消息并循环重复（但我不能 100% 确定这样的顺序 在所有条件下都相同 )。

这种行为对我来说很奇怪：我希望所有实例同时收到消息。

有人能解释一下为什么会这样吗？

如何通过单击发送按钮向所有实例发送消息？

【参考方案1】：

所以我终于找到了一个解决方案（不确定它是否最佳 - 但它正在工作）。它基于使用 NamedPipeClientStream.NumberOfServerInstances。

public void Send(string SendStr, string PipeName, int TimeOut = 1000)

    try
    
        NamedPipeClientStream pipeStream = new NamedPipeClientStream
          (".", PipeName, PipeDirection.Out, PipeOptions.Asynchronous);

        // The connect function will indefinitely wait for the pipe to become available
        // If that is not acceptable specify a maximum waiting time (in ms)
        pipeStream.Connect(TimeOut); 

        int _serverCount = pipeStream.NumberOfServerInstances; 

        byte[] _buffer = Encoding.UTF8.GetBytes(SendStr);
        pipeStream.BeginWrite(_buffer, 0, _buffer.Length, new AsyncCallback(AsyncSend), pipeStream);

        //there is more than 1 server present
        for (int i = 1; i < _serverCount; i++)
            
                //create another client copy and use it
                NamedPipeClientStream pipeStream2 = new NamedPipeClientStream
                (".", PipeName, PipeDirection.Out, PipeOptions.Asynchronous);

                pipeStream2.Connect(TimeOut);

                byte[] buffer2 = Encoding.UTF8.GetBytes(SendStr);
                pipeStream2.BeginWrite(buffer2, 0, buffer2.Length, AsyncSend, pipeStream2);
            
    
    catch (TimeoutException oEX)
        ...        

请注意，此代码无法处理 NumberOfServerInstances 在循环运行时发生变化的情况（服务器实例突然关闭等）

顺便说一句不知道为什么 MSDN 建议使用

 // Kill original sever and create new wait server
 pipeServer.Close();
 pipeServer = null;
 pipeServer = new NamedPipeServerStream(_pipeName, PipeDirection.In, 
    -1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous);

 // Recursively wait for the connection again and again....
 pipeServer.BeginWaitForConnection(
   new AsyncCallback(WaitForConnectionCallBack), pipeServer);

相反，我只是简单地断开了当前客户端的连接

pipeServer.Disconnect();

// Recursively wait for the connection again and again....
pipeServer.BeginWaitForConnection(
   new AsyncCallback(WaitForConnectionCallBack), pipeServer);

它对我也一样。

【讨论】：

我不是专家，但我猜pipeServer = null; 逻辑是试图“帮助”垃圾收集器。但是，由于它实现了 IDisposable，因此“使用”块可能更有用。