C# Tcp 异步套接字数据读取逻辑

Question

我正在开发一个 C# Tcp Async 套接字服务器程序，该程序将简单地读取套接字数据并将其放入文件中。现在的问题是在发送实际文件内容之前，我正在发送客户端名称和文件名。请注意，我通过以下方式使用简单的 send() API 从 C++ MFC 应用程序发送这些数据。

CString csInitData = "Client_Name | File_Name <EOF>";
send(hSocket, (LPCTSTR)csInitData, csInitData.GetLength(), 0);

现在我如何在异步回调函数下面接收这些数据？无法弄清楚字节分解逻辑。

public void OnDataReceived(IAsyncResult ar)
{
  StateObject state = (StateObject)ar.AsyncState;
  Socket clientSocket = state.m_currentSocket;

  int bytesRead = clientSocket.EndReceive(ar);
  if (bytesRead > 0)
  {
    //HERE I WANT TO RECEIVE THOSE DATA AND CREATE FOLDER AND FILE WITH THOSE NAMES RECEIVED FROM CLIENT
    //Process 'state.dataBuffer'//DATA INSIDE THIS BYTE BUFFER

    string fileName = "";       //FILE NAME SHOULD GO HERE
    string folderName = "";     //CLIENT NAME SHOULD GO HERE

    BinaryWriter writer;

    if (!File.Exists(folderName+fileName))
    { 
      Directory.CreateDirectory(folderName);
      writer = new BinaryWriter(File.Open(folderName+fileName, FileMode.Create));
    } 
    else
    {
      writer = new BinaryWriter(File.Open(folderName+fileName, FileMode.Append));
    }

    writer.Write(state.dataBuffer, 0, bytesRead);
    writer.Flush();
    writer.Close();

    // Recursively receive the rest file. 
    try
    {
      clientSocket.BeginReceive(state.dataBuffer, 0, StateObject.BufferSize, 0, new AsyncCallback(OnDataReceived), state);
    }
    catch
    {
      if (!clientSocket.Connected)
      {
        MessageBox.Show("Catched from OnDataReceived!");
      }
    }
  }
  else
  {
    // Signal if all the file received. 
  }
}

Answer 1

对于缓冲，听起来你想要MemoryStream：

// Somewhere to put the data:
// for simplicity, I'll assume an instance field is fine; could
// also be tracked via async-state object, if preferred
private MemoryStream backlog = new MemoryStream();

if (bytesRead > 0)
{
    // we want to append, so move to the end
    backlog.Position = backlog.Length;

    // copy new data into the buffer
    backlog.Write(state.dataBuffer, 0, bytesRead);

    ...         
} 

一般反馈：

• 不要在这里使用BinaryWriter； Stream 就可以了
• 在文件流上使用using
• 在字段中有缓存的委托实例，因此您不需要每次都 new 委托（如果您将目标实例作为状态传递，这甚至可以是 static）
• 使用Path.Combine，最好提前一次，以避免大量字符串连接
• 检查同步完成；在回调中，检查CompletedSynchronously，如果是true，则立即退出；当开始工作时，捕获IAsyncResult，检查CompletedSynchronously，如果true，则立即在同一线程上处理
• 考虑迁移到更新的异步 API - ReceiveAsync（不过，这是一个相当大的变化）
• 不要通过 IO 方法MessageBox