这个问题在TX 面试的时候问过我。 不过当时demo并没有注意这个问题， 还好面试官换问题了。。

一、正常关闭    

        如果客户端是主动申请close ， 会发送一串byte数 为0的数据到服务器，服务器就会收到count个数为0，则表示正常关闭。此时服务器正常操作close（这里有个问题是，即便客户端自己正常发送空数据进来，服务器也不会收到0数据，所以当服务器收到0的时候就代表客户端请求正常关闭）。

二、异常关闭    

        如果客户端强制点了X ，则代表未经过（退出游戏）正常关闭操作，当服务器捕获异常（远程主机强制关闭），则停止这个socket连接

using System;using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Sockets;
using System.Net;namespace TcpServer
{class Program{static byte[] dataBuffer = new byte[1024];static void Main(string[] args){StartServerAsync();Console.ReadKey();}static void StartServerAsync(){Socket socketServer = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);IPAddress iPAddress = IPAddress.Parse("192.168.200.1");IPEndPoint iPEndPoint = new IPEndPoint(iPAddress, 88);socketServer.Bind(iPEndPoint);socketServer.Listen(10);//Socket clientSocket = socketServer.Accept(); 下面支持多个客户端，改为异步， 之前c++服务器用的epoll这里似乎不需要关注socketServer.BeginAccept(AcceptCallBack, socketServer); }static void AcceptCallBack(IAsyncResult ar){Socket socketServer = ar.AsyncState as Socket;Socket socketClient = socketServer.EndAccept(ar);string msg = "Hello"; socketClient.Send(System.Text.Encoding.UTF8.GetBytes(msg));  socketClient.BeginReceive(dataBuffer, 0, 1024, SocketFlags.None, ReceiveCallBack, socketClient);socketServer.BeginAccept(AcceptCallBack, socketServer);}static void ReceiveCallBack(IAsyncResult ar){//            ar.AsyncState 可以获得之前传递的objectSocket socketClient=null ;try{socketClient = ar.AsyncState as Socket;int count = socketClient.EndReceive(ar);if (count == 0){//即便是空数据也不会是0，客户端不会发送空数据，  只有在结束时才有0的可能性socketClient.Close();return;}string msgReceive = Encoding.UTF8.GetString(dataBuffer, 0, count);Console.WriteLine(msgReceive);socketClient.BeginReceive(dataBuffer, 0, 1024, SocketFlags.None, ReceiveCallBack, socketClient);} catch (Exception e){   Console.WriteLine(e);if (socketClient != null){socketClient.Close();}}    }void StartServerSync(){Socket socketServer = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);IPAddress iPAddress = IPAddress.Parse("192.168.200.1");IPEndPoint iPEndPoint = new IPEndPoint(iPAddress, 88);socketServer.Bind(iPEndPoint);socketServer.Listen(10);Socket clientSocket = socketServer.Accept();string msg = "Hello";clientSocket.Send(System.Text.Encoding.UTF8.GetBytes(msg));byte[] databuffer = new byte[1024];int count = clientSocket.Receive(databuffer);string megReceive = System.Text.Encoding.UTF8.GetString(databuffer, 0, count);Console.Write(databuffer);clientSocket.Close();socketServer.Close();}}
}

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原文链接：https://blog.csdn.net/qq_33951440/article/details/79863661

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