在 .NET Core 3.1 中关闭 C# 套接字的正确方法是什么？答案

【问题标题】：What is the proper way to close a C# Socket in .NET Core 3.1?在 .NET Core 3.1 中关闭 C# 套接字的正确方法是什么？
【发布时间】：2021-05-04 05:46:45
【问题描述】：

问题

我正在尝试处理我的应用程序的断开连接，到目前为止我尝试过的任何方法都失败了，我尝试从服务器端断开连接，我尝试从客户端断开连接，但两端都收到问题，我正在尝试什么这里的实现是通过 QUIT 命令断开应用程序，而不必从关闭图标关闭它，因为它会引发异常

client.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace MessengerConsole
{
class Client
{
    static string username;
    static int port = 8888;
    static IPAddress clientIP;
    static Socket serverSocket;
    static Thread processThread;
    static bool connected = false;

    static string GetIp()
    {
        Console.WriteLine("Type the server ip:");
        String clientIP = Console.ReadLine();
        Console.WriteLine("Client IP: " + clientIP);
        //return clientIP;
        //temp solution
        return "192.168.0.106";
    }

    static void printSession()
    {
        Console.Clear();
        Console.WriteLine("//=====================================================");
        Console.WriteLine("//                       Session Details               ");
        Console.WriteLine("//                    =====================");
        Console.WriteLine("//                    IP: " + clientIP + "\n//                    Time: " + DateTime.Now);
        Console.WriteLine("//=====================================================");
    }
    static void clientReceiver()
    {
        while (true)
        {
            Thread.Sleep(500);
            byte[] buffer = new byte[300];
            int rece = serverSocket.Receive(buffer, 0, buffer.Length, 0);
            Array.Resize(ref buffer, rece);
            if (connected == false)
            {
                Console.WriteLine("[" + DateTime.Now.ToString() + "] " + Encoding.Default.GetString(buffer) + " Connected!");
                connected = true;
            }

            else
            {

                if (Encoding.Default.GetString(buffer) == "QUIT")
                {
                    //Quit
                    Console.WriteLine("Server Shutdown");
                    serverSocket.Shutdown(SocketShutdown.Both);
                    serverSocket.Close();
                   
                }
                else
                {
                    Console.WriteLine("[" + DateTime.Now.ToString() + "] " + Encoding.Default.GetString(buffer));
                }

            }
        }
    }



    public static void StartClient()
    {
        processThread = new Thread(clientReceiver);
        Console.WriteLine("Please enter your name");
        username = Console.ReadLine();
        clientIP = IPAddress.Parse(GetIp());  //Returns IP from GetIP()
        Console.WriteLine("Please enter HostPort");
        //string portString = Console.ReadLine();
        //temp port
        string portString = "80";
        try
        {
            port = Convert.ToInt32(portString);
        }
        catch
        {
            port = 8888;
        }
        try
        {

            serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            serverSocket.Connect(new IPEndPoint(clientIP, port));
            processThread.Start();
            byte[] name = Encoding.Default.GetBytes(username);
            
            //Send Name
            serverSocket.Send(name);
           // byte[] data = Encoding.Default.GetBytes("<" + username + "> Connected");
            //serverSocket.Send(data, 0, data.Length, 0);
            printSession();
            while (serverSocket.Connected)
            {
                //byte[] sdata = Encoding.Default.GetBytes("<" + username + ">" + Console.ReadLine());
                byte[] sdata = Encoding.Default.GetBytes(Console.ReadLine());
                if(Encoding.Default.GetString(sdata) == "QUIT")
                {
                    serverSocket.Send(sdata, sdata.Length, 0);
                    serverSocket.Shutdown(SocketShutdown.Both);
                    serverSocket.Disconnect(true);
                    serverSocket.Close();
                }

                else
                {
                    serverSocket.Send(sdata, 0, sdata.Length, 0);
                }

            }
        }
        catch (Exception e)
        {
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine(e.Message);
            Console.ForegroundColor = ConsoleColor.White;
        }

    }
}
}

server.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Net.Sockets;
using System.Net;
using System.Threading;

namespace MessengerConsole
{
class Server
{

    //Server Socket
    static Socket serverSocket;
    //Client Socket
    static Socket clientSocket;

    //Other Variables
    static int port = 8888;
    static IPAddress serverIP;
    static Thread processThread;
    static string username;
    static bool connected = false;
    //Function returns IP Address
    static string GetIp()
    {
        //Computer Name
        string hostname = Dns.GetHostName();

        /*The IPHostEntry class associates a Domain Name System (DNS) host name with an array of aliases and 
         * an array of matching IP addresses.
         */
        IPHostEntry ipentry = Dns.GetHostEntry(hostname);

        //The Address
        IPAddress[] ipAddress = ipentry.AddressList;

        return ipAddress[ipAddress.Length - 1].ToString();
    }

    static void printSession()
    {
        Console.Clear();
        Console.WriteLine("//=====================================================");
        Console.WriteLine("//                       Session Details               ");
        Console.WriteLine("//                    =====================");
        Console.WriteLine("//                    You are hosting the server");
        Console.WriteLine("//                    Time: " + DateTime.Now);
        Console.WriteLine("//=====================================================");
    }
    //Receive
    static void serverReciever()
    {
        while (true)
        {
            Thread.Sleep(500);
            byte[] buffer = new byte[300];
            int rece = clientSocket.Receive(buffer, 0, buffer.Length, 0);
            Array.Resize(ref buffer, rece);

            if (connected == false)
            {
                Console.WriteLine("[" + DateTime.Now.ToString() + "] " + Encoding.Default.GetString(buffer) + " Connected!");
                connected = true;
            }

            else
            {
                if(Encoding.Default.GetString(buffer) == "QUIT")
                {
                    //Quit
                    Console.WriteLine("Client disconnected from the chat");
                    clientSocket.Shutdown(SocketShutdown.Both);
                    clientSocket.Close();
                }
                else
                {
                    Console.WriteLine("[" + DateTime.Now.ToString() + "] " + Encoding.Default.GetString(buffer));
                }

            }
        }
    }



    public static void StartServer()
    {
        //Thread
        processThread = new Thread(serverReciever);

        //Display
        Console.WriteLine("Your Local Ip is " + GetIp());
        Console.WriteLine("Please enter your name");
        username = Console.ReadLine();
        Console.WriteLine("Please enter HostPort");
        //  string portString = Console.ReadLine();
        //temp solution
        string portString = "80";
        try
        {
            port = Convert.ToInt32(portString);
        }
        catch
        {
            port = 8888;
        }

        try
        {
            //GetIp returns string
            serverIP = IPAddress.Parse(GetIp());
            //TCP Socket
            serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            serverSocket.Bind(new IPEndPoint(serverIP, port));
            serverSocket.Listen(0);

            //Server Socket listening for client requests
            clientSocket = serverSocket.Accept();
            printSession();
            processThread.Start();
            byte[] name = Encoding.Default.GetBytes(username);
            clientSocket.Send(name);
            while (true)
            {
                byte[] sdata = Encoding.Default.GetBytes(Console.ReadLine());
                clientSocket.Send(sdata, 0, sdata.Length, 0);
            }
        }
        catch
        {
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine("Server already open!");
            Console.ForegroundColor = ConsoleColor.White;
        }
    }
}
}

这是我收到的错误

未处理的异常。 System.ObjectDisposedException：无法访问已处置的对象。对象名称：“System.Net.Sockets.Socket”。在 System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags, SocketError& errorCode) at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, C:\Users\MessengerConsoleAppV2\MessengerConsole\Client.cs 中 MessengerConsole.Client.clientReceiver() 的 SocketFlags socketFlags)：System.Threading.ThreadHelper.ThreadStart_Context(Object state) 中 System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext) 的第 42 行, ContextCallback 回调, 对象状态) --- 在 System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) 的 System.Threading.ThreadHelper.ThreadStart 的上一个引发异常的位置结束堆栈跟踪()

我尝试使用 Socket.Disconnect() 、 Socket.Close() 、 Socket.Dispose() ，它们都产生相同的结果

编辑：

在

中添加return

if(Encoding.Default.GetString(sdata) == "QUIT")
            {
                serverSocket.Send(sdata, sdata.Length, 0);
                serverSocket.Shutdown(SocketShutdown.Both);
                serverSocket.Close();
                return;
            }

在服务器端没有错误，但客户端仍然抛出正在访问的已处置对象的异常

未处理的异常。 System.ObjectDisposedException：无法访问已处置的对象。对象名称：“System.Net.Sockets.Socket”。在 System.Net.Sockets.Socket.Receive（字节 [] 缓冲区，Int32 偏移量，Int32 大小，SocketFlags socketFlags，SocketError&errorCode）在 System.Net.Sockets.Socket.Receive(Byte[] 缓冲区，Int32 偏移量，Int32 大小，SocketFlags socketFlags) 在 C:\Users\MessengerConsoleAppV2\MessengerConsole\Client.cs:line 44 中的 MessengerConsole.Client.clientReceiver() 在 System.Threading.ThreadHelper.ThreadStart_Context（对象状态）在 System.Threading.ExecutionContext.RunInternal（ExecutionContext executionContext，ContextCallback 回调，对象状态） --- 从先前抛出异常的位置结束堆栈跟踪 --- 在 System.Threading.ExecutionContext.RunInternal（ExecutionContext executionContext，ContextCallback 回调，对象状态）在 System.Threading.ThreadHelper.ThreadStart()

【问题讨论】：

标签： c# .net sockets .net-core asp.net-core-3.1

【解决方案1】：

在与QUIT 相关的所有代码位置中，您只关闭和处理套接字，而不是从服务该套接字的无限循环返回。我认为当Connected 属性在已处置的套接字上评估时，此堆栈会在下一次迭代中抛出，请尝试在关闭套接字后添加return 语句。

【讨论】：

当我在 serverSocket.Close() 下添加 'return' 时，下一次迭代中抛出的堆栈是正确的；它工作得很好，但我在客户端仍然有一个错误，receiver() 仍在等待从服务器接收数据并且再次抛出相同的异常（我将在我的答案中编辑它）
您正在使用SocketShutdown.Both，这是一种优雅地停止网络对话的坏方法。在此处查看答案 stackoverflow.com/questions/32397370/…> 也许会有所帮助。或者您可以将套接字操作包装在 try catch 块中，捕获 ObjectDisposedException 并在那里添加 return，静默丢弃异常。
ObjectDisposedException 是临时修复，我会将您的解释标记为答案