AsyncCallback未触发

Question

试图在WinForms中实现异步客户端/服务器应用程序。客户方代码如下：

using System; 
using System.Net; 
using System.Net.Sockets; 
using System.Text; 
using System.Threading; 
using System.Threading.Tasks; 
using System.Windows.Forms; 

namespace AsyncClient 
{ 
    public partial class AsyncClient : Form 
    { 
     public AsyncClient() 
     { 
      InitializeComponent(); 
     } 

     //ManualResetEvent for notifying asyncronous threads that an event has occured 
     private static ManualResetEvent connectDone = new ManualResetEvent(false); 
     private static ManualResetEvent sendDone = new ManualResetEvent(false); 
     private static ManualResetEvent receiveDone = new ManualResetEvent(false); 

     //Response from the remote device (server) 
     private static String response = String.Empty; 

     //start client 
     private void button1_Click(object sender, EventArgs e) 
     { 
      TcpClient clientSocket = new TcpClient(); 
      try 
      { 
       var message = System.Text.Encoding.UTF8.GetBytes(txtFromClient.Text); //convert message to bytes for sending over the wire 
       using (clientSocket)/*(var clientSocket = new TcpClient("127.0.0.1", 1234)) *///make connection with the host 
       { 
        clientSocket.BeginConnect(IPAddress.Loopback, 1234, new AsyncCallback(connectCallBack), clientSocket); 
        sendDone.WaitOne(); 
        lblConnectionStatus.Text = "Connect is successfully established with the remote device."; 
        //send data to remote device 
        NetworkStream stream = clientSocket.GetStream(); //obtain network stream 
        stream.Write(message, 0, message.Length); //send data to the remote device 
        //sendDone.WaitOne(); 
       } 
      } 
      finally 
      { 
       clientSocket.Close(); 
      } 
     } 

     private static void connectCallBack(IAsyncResult ar) 
     { 
      try 
      { 
       var clientSocket = (TcpClient)ar.AsyncState; //retrieve socket from state object (IAsyncResult) 
       clientSocket.EndConnect(ar); //complete the connection 
       connectDone.Set(); 
      } 
      finally 
      { 

      } 
     } 

     private void txtFromClient_Click(object sender, EventArgs e) 
     { 
      txtFromClient.Text = ""; 
     } 
    } 
} 

当我button1发送文本，UI被冻结。在dubug模式我发现，在一行AsyncCallback(connectCallBack)

clientSocket.BeginConnect(IPAddress.Loopback, 1234, new AsyncCallback(connectCallBack), clientSocket); 

不点火，因此没有被执行connectCallBack。程序停止在线

sendDone.WaitOne(); 

任何想法为什么？有人可以帮忙吗？

Answer 1

您正在等待sendDone.WaitOne();，并在您回电您使用

connectDone.Set(); 

你应该connectDone.WaitOne();

Answer 2

为什么UI被冻结更换sendDone.WaitOne();：因为您要在主连接线程使UI变得无法响应。这是因为UI在主线程上运行。为了解决这个问题，请尝试连接或接收与主要威胁不同的线索。

为何回调不叫：你应该更换sendDone.WaitOne();与connectDone.WaitOne();因为你设置connectDone.Set()，你正在等待sendDone.WaitOne();