C# 中套接字标识符的 TCP 套接字服务器自定义 class

Question

我一直在查看许多 tcp client/server 示例，想知道如何创建一种方法来识别每个客户端。我知道的一种方法是通过登录身份验证。我知道如何连接和查询数据库，但是在成功验证后我怎么说，获取用户名并说这个用户名就是这个套接字。 class 示例或简单方法将被视为示例。我希望能够通过数据库中的用户名分别定位所有连接的客户端。

我为服务器使用的示例

 using System;

    using System.Collections.Generic;

    using System.Net;

    using System.Net.Sockets;

    using System.Text;



    namespace MultiServer

    {

        class Program

        {

            private static readonly Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            private static readonly List<Socket> clientSockets = new List<Socket>();

            private const int BUFFER_SIZE = 2048;

            private const int PORT = 100;

            private static readonly byte[] buffer = new byte[BUFFER_SIZE];



            static void Main()

            {

                Console.Title = "Server";

                SetupServer();

                Console.ReadLine(); // When we press enter close everything

                CloseAllSockets();

            }



            private static void SetupServer()

            {

                Console.WriteLine("Setting up server...");

                serverSocket.Bind(new IPEndPoint(IPAddress.Any, PORT));

                serverSocket.Listen(0);

                serverSocket.BeginAccept(AcceptCallback, null);

                Console.WriteLine("Server setup complete");

            }



            /// <summary>

            /// Close all connected client (we do not need to shutdown the server socket as its connections

            /// are already closed with the clients).

            /// </summary>

            private static void CloseAllSockets()

            {

                foreach (Socket socket in clientSockets)

                {

                    socket.Shutdown(SocketShutdown.Both);

                    socket.Close();

                }



                serverSocket.Close();

            }



            private static void AcceptCallback(IAsyncResult AR)

            {

                Socket socket;



                try

                {

                    socket = serverSocket.EndAccept(AR);

                }

                catch (ObjectDisposedException) // I cannot seem to avoid this (on exit when properly closing sockets)

                {

                    return;

                }



               clientSockets.Add(socket);

               socket.BeginReceive(buffer, 0, BUFFER_SIZE, SocketFlags.None, ReceiveCallback, socket);

               Console.WriteLine("Client connected, waiting for request...");

               serverSocket.BeginAccept(AcceptCallback, null);

            }



            private static void ReceiveCallback(IAsyncResult AR)

            {

                Socket current = (Socket)AR.AsyncState;

                int received;



                try

                {

                    received = current.EndReceive(AR);

                }

                catch (SocketException)

                {

                    Console.WriteLine("Client forcefully disconnected");

                    // Don't shutdown because the socket may be disposed and its disconnected anyway.

                    current.Close(); 

                    clientSockets.Remove(current);

                    return;

                }



                byte[] recBuf = new byte[received];

                Array.Copy(buffer, recBuf, received);

                string text = Encoding.ASCII.GetString(recBuf);

                Console.WriteLine("Received Text: " + text);



                if (text.ToLower() == "get time") // Client requested time

                {

                    Console.WriteLine("Text is a get time request");

                    byte[] data = Encoding.ASCII.GetBytes(DateTime.Now.ToLongTimeString());

                    current.Send(data);

                    Console.WriteLine("Time sent to client");

                }

                else if (text.ToLower() == "exit") // Client wants to exit gracefully

                {

                    // Always Shutdown before closing

                    current.Shutdown(SocketShutdown.Both);

                    current.Close();

                    clientSockets.Remove(current);

                    Console.WriteLine("Client disconnected");

                    return;

                }

                else

                {

                    Console.WriteLine("Text is an invalid request");

                    byte[] data = Encoding.ASCII.GetBytes("Invalid request");

                    current.Send(data);

                    Console.WriteLine("Warning Sent");

                }



                current.BeginReceive(buffer, 0, BUFFER_SIZE, SocketFlags.None, ReceiveCallback, current);

            }

        }

    }

Answer 1

当您使用异步回调时，有一个非常简单的解决方案（尽管我强烈建议切换到更新的方法，或者更好的是，现有的库 - 原始 TCP 很难做到正确）。

回调委托可以指向一个实例方法。这意味着你可以有这样的东西：

class Client
{
  private readonly Socket socket;
  public readonly byte[] ReceiveBuffer = new byte[BUFFFER_SIZE];

  public Client(Socket socket)
  {
    this.socket = socket;
  }

  public void ReceiveCallback(IAsyncResult AR)
  {
    // Handle the received data as usual
  }
}

然后在您的 AcceptCallback 方法中，只需使用 Client 列表而不是 Socket，最后的 BeginReceive 调用如下：

var client = new Client(socket);
socket.BeginReceive(client.ReceiveBuffer, 0, BUFFER_SIZE, SocketFlags.None, client.ReceiveCallback, 
                    socket);
clients.Add(newClient);

但同样，编写自定义网络很难。尽可能使用现有的解决方案 - 有很多选择。

此外，您得到的 ObjectDisposedException 是因为您在 Shutdown 之后紧跟着 Close。这是错误的。 TCP 关闭是协作式的——在调用套接字上的 Close 之前，您需要等待客户端套接字关闭。您正在做的是在连接有机会自行解决之前粗暴地中断连接。再次重申 - TCP 很难做到正确，您需要非常彻底地了解它的工作原理。

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