异步socket的线程分配（C＃）

 

    以下是MSDN里异步socket示例的代码，我在代码里加入了显示当前线程ID的语句，想看看异步socket的线程是怎么分配的，与客户端配合运行后的结果如图

Code
Server端代码：
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;


namespace ConsoleServer
{
    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();  
    }


    class Program
    {
        public static ManualResetEvent allDone = new ManualResetEvent(false);
        
        /**//// <summary>
        ///监听
        /// 并开始接受网络连接请求的方法
        /// </summary>
        public static void StartListening()
        {
            Console.WriteLine("监听时的线程:" + Thread.CurrentThread.ManagedThreadId.ToString());
            // Data buffer for incoming data.
            byte[] bytes = new Byte[1024];

            // Establish the local endpoint for the socket.
            // The DNS name of the computer
            // running the listener is "host.contoso.com".
            IPHostEntry ipHostInfo = Dns.Resolve("127.0.0.1");
            IPAddress ipAddress = ipHostInfo.AddressList[0];
            IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 9090);

            // 创建一个tcp/ip socket
            Socket listener = new Socket(AddressFamily.InterNetwork,
                SocketType.Stream, ProtocolType.Tcp);

            // Bind the socket to the local endpoint and listen for incoming connections.
            try
            {
                listener.Bind(localEndPoint);
                Console.WriteLine("Listen1: " + Thread.CurrentThread.ManagedThreadId.ToString());
                listener.Listen(100);
                Console.WriteLine("Listen2:  " + Thread.CurrentThread.ManagedThreadId.ToString());

                while (true)
                {
                    Console.WriteLine("1:  " + Thread.CurrentThread.ManagedThreadId.ToString());
                    // Set the event to nonsignaled state.设置为无信号状态
                    allDone.Reset();
                    Console.WriteLine("2: " + Thread.CurrentThread.ManagedThreadId.ToString());
                    // Start an asynchronous socket to listen for connections.
                    Console.WriteLine("Waiting for a connection");
                    //开始建立连接
                    listener.BeginAccept(
                        new AsyncCallback(AcceptCallback),
                        listener);
                    Console.WriteLine("3:  " + Thread.CurrentThread.ManagedThreadId.ToString());
                    // Wait until a connection is made before continuing.

                    allDone.WaitOne();
                    Console.WriteLine("4: " + Thread.CurrentThread.ManagedThreadId.ToString());
                }

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

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

        }

        /**//// <summary>
        /// 处理连接请求
        /// 并开始接收网络数据的回调方法
        /// </summary>
        /// <param name="ar"></param>
        public static void AcceptCallback(IAsyncResult ar)      
        {
            // Signal the main thread to continue.
            allDone.Set();
            Console.WriteLine("AcceptCallback1线程ID为:  "+ Thread.CurrentThread.ManagedThreadId.ToString());
            // Get the socket that handles the client request.
            Socket listener = (Socket)ar.AsyncState;
            //建立socket通道，连接建立完成
            Socket handler = listener.EndAccept(ar);
            
            // Create the state object.创建一个状态对象，开始接受数据
            StateObject state = new StateObject();
            state.workSocket = handler;
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
            Console.WriteLine("AcceptCallback2线程ID为:   " + Thread.CurrentThread.ManagedThreadId.ToString());
        }


        /**//// <summary>
        /// 结束接收数据的回调方法
        /// </summary>
        /// <param name="ar"></param>
        public static void ReadCallback(IAsyncResult ar)
        {
            Console.WriteLine("ReadCallback线程ID为:   " + Thread.CurrentThread.ManagedThreadId.ToString());
            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.从socket通道里读取数据
            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("<EOF>") > -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);

                    Console.WriteLine("请输入要发送的信息：");
                    string str = Console.ReadLine();
                    Send(handler, str + "<EOF>");

                    //Send(handler, content);
                    
                    
                }
                else
                {
                    // Not all data received. Get more.
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReadCallback), state);
                }
            }
        }


        /**//// <summary>
        /// 开始发送数据的方法
        /// </summary>
        /// <param name="handler"></param>
        /// <param name="data"></param>
        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);
        }


        /**//// <summary>
        /// 结束发送数据的回调方法
        /// </summary>
        /// <param name="ar"></param>
        private static void SendCallback(IAsyncResult ar)
        {
            Console.WriteLine("SendCallback线程ID为:   " + Thread.CurrentThread.ManagedThreadId.ToString());
            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);

                //没有了这两句，server是发不出去的，为什么呢？
                handler.Shutdown(SocketShutdown.Both);
                handler.Close();

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


        static void Main(string[] args)
        {
            Console.WriteLine("main线程ID为:   " + Thread.CurrentThread.ManagedThreadId.ToString());
            StartListening();
            Console.ReadLine();
        }
    }
}



客户端代码：
using System;
using System.Collections.Generic;
using System.Text;
using System.Net.Sockets;
using System.Threading;
using System.Net;


namespace WindowsClient
{
    public class StateObject
    {
        // Client socket.
        public Socket workSocket = null;
        // Size of receive buffer.
        public const int BufferSize = 256;
        // Receive buffer.
        public byte[] buffer = new byte[BufferSize];
        // Received data string.
        public StringBuilder sb = new StringBuilder();
    }


   class Program
   {
        // The port number for the remote device.
        private const int port = 9090;
        

        // ManualResetEvent instances signal completion.
        private static ManualResetEvent connectDone = 
            new ManualResetEvent(false);
        private static ManualResetEvent sendDone = 
            new ManualResetEvent(false);
        private static ManualResetEvent receiveDone = 
            new ManualResetEvent(false);

        // The response from the remote device.
        private static String response = String.Empty;

        private static void StartClient() 
        {
            string str = string.Empty;
            // Connect to a remote device.
            try {
                // Establish the remote endpoint for the socket.
                // The name of the 
                // remote device is "host.contoso.com".
                IPHostEntry ipHostInfo = Dns.Resolve("127.0.0.1");
                IPAddress ipAddress = ipHostInfo.AddressList[0];
                IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);

                // Create a TCP/IP socket.
                Socket client = new Socket(AddressFamily.InterNetwork,
                    SocketType.Stream, ProtocolType.Tcp);

                // Connect to the remote endpoint.
                client.BeginConnect( remoteEP,
                    new AsyncCallback(ConnectCallback), client);
                connectDone.WaitOne();
                Console.WriteLine("请输入要发送的信息：");
               // str = Console.ReadLine();
                // Send test data to the remote device.
                Send(client, str + "<EOF>");//"This is a test<EOF>");
                sendDone.WaitOne();
               
                // Receive the response from the remote device.
                Receive(client);
                receiveDone.WaitOne();
                
                // Write the response to the console.
                Console.WriteLine("Response received : {0}", response);

                // Release the socket.
                client.Shutdown(SocketShutdown.Both);
                client.Close();
                
            } 
            catch (Exception e) 
            {
                Console.WriteLine(e.ToString());
            }
        }

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

                // Complete the connection.
                client.EndConnect(ar);

                Console.WriteLine("Socket connected to {0}",
                    client.RemoteEndPoint.ToString());

                // Signal that the connection has been made.
                connectDone.Set();
            } 
            catch (Exception e) 
            {
                Console.WriteLine(e.ToString());
            }
        }


        private static void Receive(Socket client)
        {
            try 
            {
                // Create the state object.
                StateObject state = new StateObject();
                state.workSocket = client;

                // Begin receiving the data from the remote device.
                client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReceiveCallback), state);
            } 
            catch (Exception e) 
            {
                Console.WriteLine(e.ToString());
            }
        }


        private static void ReceiveCallback( IAsyncResult ar )
        {
            try 
            {
                // Retrieve the state object and the client socket 
                // from the asynchronous state object.
                StateObject state = (StateObject) ar.AsyncState;
                Socket client = state.workSocket;

                // Read data from the remote device.
                int bytesRead = client.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));

                    // Get the rest of the data.
                    client.BeginReceive(state.buffer,0,StateObject.BufferSize,0,
                        new AsyncCallback(ReceiveCallback), state);
                } 
                else 
                {
                    // All the data has arrived; put it in response.
                    if (state.sb.Length > 1) 
                    {
                        response = state.sb.ToString();
                    }
                    // Signal that all bytes have been received.
                    receiveDone.Set();
                }
            } 
            catch (Exception e) 
            {
                Console.WriteLine(e.ToString());
            }
        }


        private static void Send(Socket client, 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.
            client.BeginSend(byteData, 0, byteData.Length, 0,
                new AsyncCallback(SendCallback), client);
        }

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

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

                // Signal that all bytes have been sent.
                sendDone.Set();
            } 
            catch (Exception e) 
            {
                Console.WriteLine(e.ToString());
            }
        } 

   
        static void Main(string[] args)
        {
            StartClient();
            Console.ReadLine();
        }
    }
}

 

根据MSDN的原话：

“异步套接字使用系统线程池中的线程处理传入的连接。

一个线程负责接受连接，

另一线程用于处理每个传入的连接，

还有一个线程负责接收连接数据。

这些线程可以是同一个线程，具体取决于线程池所分配的线程。”

个人理解：根据MSDN对异步socket连接、接受、发送等线程分配的解释，以及上面代码的注释和演示，我们在做异步socket编程时，不用对socket这组线程做任何处理，只要处理好主线程及其它线程与socket这周线程的关系就可。

 

补充：在main方法和AcceptCallback方法里分别加入
bool threadBool = Thread.CurrentThread.IsBackground;
Console.WriteLine(threadBool.ToString());
这两条语句，则会发现main方法里线程的IsBackground属性为false，AcceptCallback方法里线程的IsBackground属性为True；MSDN里说：“托管线程池中的线程为后台线程，即它们的 IsBackground 属性为 true”；再根据上面引用的MSDN的原文“这些线程可以是同一个线程，具体取决于线程池所分配的线程。”的这一句可知，此线程就是由线程池所分配的，也许有人会认为此补充为多此一举，但是我最初对于这几个线程的出现，以及MSDN的解释没有很好的理解，所以出现了这个补充，现在好了，我知道了这几个隐藏的线程出自那里了，呵呵，你呢？

再次补充：
//如果要查看线程是否属于托管线程池，可使用
   bool poolThread = Thread.CurrentThread.IsThreadPoolThread;//指示线程是否属于托管线程池

希望对异步socket及线程了解比较深入的同学，能给出更多的建议和指导