在异步套接字中向特定客户端发送数据

Posted 2023-04-12

【中文标题】在异步套接字中向特定客户端发送数据

【英文标题】：Send data to specific client in Asynchronous Socket

【发布时间】：2020-07-13 08:07:42

【问题描述】：

我使用来自this Microsoft 的异步服务器套接字示例，该服务器有许多客户端，此示例正常工作，客户端发送数据和服务器运行 ReadCallback 函数，同时 服务器可以回复这个客户端（只要收到数据就可以发送数据），我的问题是：

服务器如何在另一个时间没有来自clinet的数据向特定客户端发送数据？（当服务器要向特定客户端发送数据时） 如何保存连接的客户端并在其他时间向其中一个发送数据？（假设客户端已连接）

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

// State object for reading client data asynchronously  
public class StateObject

    // Client  socket.  
    public Socket workSocket = null;
    // Size of receive buffer.  
    public const int BufferSize = 1024;
    // Receive buffer.  
    public byte[] buffer = new byte[BufferSize];
    // Received data string.  
    public StringBuilder sb = new StringBuilder();


public class AsynchronousSocketListener

    // Thread signal.  
    public static ManualResetEvent allDone = new ManualResetEvent(false);

    static List<Socket> Connections = new List<Socket>();
    public AsynchronousSocketListener()
    
    

    public static void StartListening()
    
        // Establish the local endpoint for the socket.  
        // The DNS name of the computer  
        // running the listener is "host.contoso.com".  
        IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
        IPAddress ipAddress = ipHostInfo.AddressList[4];

        IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 1111);

        // Create a TCP/IP socket.  
        Socket listener = new Socket(ipAddress.AddressFamily,
            SocketType.Stream, ProtocolType.Tcp);
        Console.WriteLine(ipAddress.AddressFamily);
        // Bind the socket to the local endpoint and listen for incoming connections.  
        try
        
            listener.Bind(localEndPoint);
            listener.Listen(1000);
            while (true)
            
                // Set the event to nonsignaled state.  
                allDone.Reset();
                //Console.WriteLine(ipAddress.);
                // Start an asynchronous socket to listen for connections.  

                Console.WriteLine("Waiting for a connection...");

                listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);

                // Wait until a connection is made before continuing.  
                allDone.WaitOne();
            

        
        catch (Exception e)
        
            Console.WriteLine(e.ToString());
        

        Console.WriteLine("\nPress ENTER to continue...");
        Console.Read();

    

    public static void AcceptCallback(IAsyncResult ar)
    
        // Signal the main thread to continue.  
        allDone.Set();

        // Get the socket that handles the client request.  
        Socket listener = (Socket)ar.AsyncState;
        Socket handler = listener.EndAccept(ar);

        // Create the state object.  
        StateObject state = new StateObject();
        state.workSocket = handler;


        //Connections.Add(listener); Thats my try !!!
        handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
            new AsyncCallback(ReadCallback), state);
    

    public static void ReadCallback(IAsyncResult ar)
    
        String content = String.Empty;

        // Retrieve the state object and the handler socket  
        // from the asynchronous state object.  
        StateObject state = (StateObject)ar.AsyncState;
        Socket handler = state.workSocket;

        // Read data from the client socket.
        int bytesRead = handler.EndReceive(ar);

        if (bytesRead > 0)
        
            // There  might be more data, so store the data received so far.  
            state.sb.Append(Encoding.ASCII.GetString(
                state.buffer, 0, bytesRead));

            // Check for end-of-file tag. If it is not there, read
            // more data.  
            content = state.sb.ToString();
            if (content.IndexOf("\r") > -1)
            
                // All the data has been read from the
                // client. Display it on the console.  
                Console.WriteLine("Read 0 bytes from socket. \n Data : 1",
                    content.Length, content);
                // Echo the data back to the client.  
                Send(handler, content);
            
            else
            
                // Not all data received. Get more.  
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
            
        
    

    private static void Send(Socket handler, String data)
    
        // Convert the string data to byte data using ASCII encoding.  
        byte[] byteData = Encoding.ASCII.GetBytes(data);

        // Begin sending the data to the remote device.  
        handler.BeginSend(byteData, 0, byteData.Length, 0,
            new AsyncCallback(SendCallback), handler);
    

    private static void SendCallback(IAsyncResult ar)
    
        try
        
            // Retrieve the socket from the state object.  
            Socket handler = (Socket)ar.AsyncState;

            // Complete sending the data to the remote device.  
            int bytesSent = handler.EndSend(ar);
            Console.WriteLine("Sent 0 bytes to client.", bytesSent);

            handler.Shutdown(SocketShutdown.Both);
            handler.Close();

        
        catch (Exception e)
        
            Console.WriteLine(e.ToString());
        
    

    public static void Main(String[] args)
    
        //await StartListening();
        //Thread thread = new Thread();
        //thread.Start();
        new Thread(delegate () 
            StartListening();
        ).Start();
        while (true)
        
            Console.WriteLine("Connections Number : " + Connections.Count.ToString());
            foreach (var item in Connections)
            
                **Send(item, "I'm Server !");**  i want to send this message
            
            Console.ReadLine();
        
    

【参考方案1】：

当您接受连接时，将套接字保存在列表中。 你可以随时访问列表，获取你想要的socket。

【讨论】：

我之前做过，但在列表中，套接字连接状态为关闭，并且该连接是套接字上的只读属性，不适合同一个连接