C# 异步Socket 由于线程退出或应用程序请求，已放弃 I/O 操作。
本人刚接触C#异步Socket编程。当程序执行到int bytesRead = handler.EndReceive(ar)时，就会报错，“由于线程退出或应用程序请求，已放弃 I/O 操作。”不知道是为什么，还请高人指点，谢谢了。
程序如下：服务器端
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace TongEx060401
{
class Program
{
private static IPAddress myIP = IPAddress.Parse("172.25.13.51");
private static IPEndPoint myServer;
private static Socket mySocket;
private static Socket handler;
private static ManualResetEvent myReset = new ManualResetEvent(false);
static void Main(string[] args)
{
Thread threadWatch = null; //负责 调用套接字， 执行 监听请求的线程
try
{
mySocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); //定义套接字；
myServer = new IPEndPoint(myIP, 6000);
mySocket.Bind(myServer);
mySocket.Listen(200);
Console.WriteLine("启动服务器成功...");
threadWatch = new Thread(new ThreadStart(target));
//threadWatch = new Thread(target);
threadWatch.Start();
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}

}
private static void target()
{
while (true)
{
//设为非终止
//允许继续等待；
myReset.Reset();
mySocket.BeginAccept(new AsyncCallback(AcceptCallback), mySocket);
//阻塞当前线程，直到收到请求信号
myReset.WaitOne();
}
}
private static void AcceptCallback(IAsyncResult ar)
{
//将事件设为终止
myReset.Set();
Socket listener = (Socket)ar.AsyncState; //获取用户定义的对象，他限定或包含关于异步操作的信息
handler = listener.EndAccept(ar);
//获取状态
StateObject state = new StateObject();
state.workSocket = handler;
Console.WriteLine("与客户建立连接。");
try
{
byte[] byteData = System.Text.Encoding.BigEndianUnicode.GetBytes("已经准备好，请通话！");
//开始发送数据
//handler.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendCallback), handler);
}
catch (Exception ee)
{
Console.WriteLine(ee.Message);
}
Thread thread = new Thread(new ThreadStart(begReceive));
thread.Start();
}
private static void SendCallback(IAsyncResult ar)
{
myReset.Reset();
try
{
handler = (Socket)ar.AsyncState;
int bytesSent = handler.EndSend(ar);
}
catch (Exception eee)
{
Console.WriteLine(eee.Message);
}
}
private static void begReceive()
{
myReset.Reset();
StateObject state = new StateObject();
state.workSocket = handler;

handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
}
private static void ReadCallback(IAsyncResult ar)
{
myReset.Set();
StateObject state = (StateObject)ar.AsyncState;
Socket tt = state.workSocket;
//结束读取并获取读取字节数
int bytesRead = handler.EndReceive(ar); //在此处出错！
state.sb.Append(System.Text.Encoding.BigEndianUnicode.GetString(state.buffer, 0, bytesRead)); string content = state.sb.ToString();
state.sb.Remove(0, content.Length);
//重新开始读取数据
tt.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
}
}
class StateObject
{
public Socket workSocket = null;
public const int BufferSize = 1024;
public byte[] buffer = new byte[BufferSize];
public StringBuilder sb = new StringBuilder();
public StateObject()
{
}
}
}

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