C#中利用“完成埠”可實現socket程式設計的非同步通訊以及大容量併發等問題。廢話少說，直接上程式碼。MSDN中已有現成的例子，但是其中有一個類未給出。這裡全都有了。

1，主程式

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




namespace IOCPServer
{
   public class Server
    {
        private int m_numConnections;   // 最大連線數
        private int m_receiveBufferSize;// buffer size to use for each socket I/O operation 
        BufferManager m_bufferManager;  // represents a large reusable set of buffers for all socket operations
        const int opsToPreAlloc = 2;    // read, write (don't alloc buffer space for accepts)
        Socket listenSocket;            // the socket used to listen for incoming connection requests
        // pool of reusable SocketAsyncEventArgs objects for write, read and accept socket operations
        SocketAsyncEventArgsPool m_readWritePool;
        int m_totalBytesRead;           // counter of the total # bytes received by the server
        int m_numConnectedSockets;      // the total number of clients connected to the server 
        Semaphore m_maxNumberAcceptedClients;

        // Create an uninitialized server instance.  
        // To start the server listening for connection requests
        // call the Init method followed by Start method 
        //
        // <param name="numConnections">the maximum number of connections the sample is designed to handle simultaneously</param>
        // <param name="receiveBufferSize">buffer size to use for each socket I/O operation</param>
        
       public Server(int numConnections, int receiveBufferSize)
        {
            m_totalBytesRead = 0;
            m_numConnectedSockets = 0;
            m_numConnections = numConnections;
            m_receiveBufferSize = receiveBufferSize;
            // allocate buffers such that the maximum number of sockets can have one outstanding read and 
            //write posted to the socket simultaneously  
            m_bufferManager = new BufferManager(receiveBufferSize * numConnections * opsToPreAlloc,
                receiveBufferSize);

            m_readWritePool = new SocketAsyncEventArgsPool(numConnections);
            m_maxNumberAcceptedClients = new Semaphore(numConnections, numConnections);
        }

        // Initializes the server by preallocating reusable buffers and 
        // context objects.  These objects do not need to be preallocated 
        // or reused, but it is done this way to illustrate how the API can 
        // easily be used to create reusable objects to increase server performance.
        //
        public void Init()
        {
            // Allocates one large byte buffer which all I/O operations use a piece of.  This gaurds 
            // against memory fragmentation
            m_bufferManager.InitBuffer();

            // preallocate pool of SocketAsyncEventArgs objects
            SocketAsyncEventArgs readWriteEventArg;

            for (int i = 0; i < m_numConnections; i++)
            {
                //Pre-allocate a set of reusable SocketAsyncEventArgs
                readWriteEventArg = new SocketAsyncEventArgs();
                readWriteEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(IO_Completed);
                readWriteEventArg.UserToken = new AsyncUserToken();

                // assign a byte buffer from the buffer pool to the SocketAsyncEventArg object
                m_bufferManager.SetBuffer(readWriteEventArg);

                // add SocketAsyncEventArg to the pool
                m_readWritePool.Push(readWriteEventArg);
            }

        }

        // Starts the server such that it is listening for 
        // incoming connection requests.    
        //
        // <param name="localEndPoint">The endpoint which the server will listening 
        // for connection requests on</param>
        public void Start(IPEndPoint localEndPoint)
        {
            // create the socket which listens for incoming connections
            listenSocket = new Socket(localEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
            listenSocket.Bind(localEndPoint);
            // start the server with a listen backlog of 100 connections
            listenSocket.Listen(100);

            // post accepts on the listening socket
            StartAccept(null);

            //Console.WriteLine("{0} connected sockets with one outstanding receive posted to each....press any key", m_outstandingReadCount);
            Console.WriteLine("Press any key to terminate the server process....");
            Console.ReadKey();
        }


        // Begins an operation to accept a connection request from the client 
        //
        // <param name="acceptEventArg">The context object to use when issuing 
        // the accept operation on the server's listening socket</param>
        public void StartAccept(SocketAsyncEventArgs acceptEventArg)
        {
            if (acceptEventArg == null)
            {
                acceptEventArg = new SocketAsyncEventArgs();
                acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed);
            }
            else
            {
                // socket must be cleared since the context object is being reused
                acceptEventArg.AcceptSocket = null;
            }

            m_maxNumberAcceptedClients.WaitOne();
            bool willRaiseEvent = listenSocket.AcceptAsync(acceptEventArg);
            if (!willRaiseEvent)
            {
                ProcessAccept(acceptEventArg);
            }
        }

        // This method is the callback method associated with Socket.AcceptAsync 
        // operations and is invoked when an accept operation is complete
        //
        void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs e)
        {
            ProcessAccept(e);
        }

        private void ProcessAccept(SocketAsyncEventArgs e)
        {
            Interlocked.Increment(ref m_numConnectedSockets);
            Console.WriteLine("Client connection accepted. There are {0} clients connected to the server",
                m_numConnectedSockets);
           
            // Get the socket for the accepted client connection and put it into the 
            //ReadEventArg object user token
            SocketAsyncEventArgs readEventArgs = m_readWritePool.Pop();
            ((AsyncUserToken)readEventArgs.UserToken).Socket = e.AcceptSocket;

            // As soon as the client is connected, post a receive to the connection
            bool willRaiseEvent = e.AcceptSocket.ReceiveAsync(readEventArgs);
            Console.WriteLine("是否是非同步：{0} ", willRaiseEvent);
            if (!willRaiseEvent)
            {
                ProcessReceive(readEventArgs);
            }

            // Accept the next connection request
            StartAccept(e);
        }

        // This method is called whenever a receive or send operation is completed on a socket 
        //
        // <param name="e">SocketAsyncEventArg associated with the completed receive operation</param>
        void IO_Completed(object sender, SocketAsyncEventArgs e)
        {
            // determine which type of operation just completed and call the associated handler
            switch (e.LastOperation)
            {
                case SocketAsyncOperation.Receive:
                    ProcessReceive(e);
                    break;
                case SocketAsyncOperation.Send:
                    ProcessSend(e);
                    break;
                default:
                    throw new ArgumentException("The last operation completed on the socket was not a receive or send");
            }

        }

        // This method is invoked when an asynchronous receive operation completes. 
        // If the remote host closed the connection, then the socket is closed.  
        // If data was received then the data is echoed back to the client.
        //
        private void ProcessReceive(SocketAsyncEventArgs e)
        {            
            // check if the remote host closed the connection
            AsyncUserToken token = (AsyncUserToken)e.UserToken;
            if (e.BytesTransferred > 0 && e.SocketError == SocketError.Success)
            {
                byte[] arrClientSendResult = new byte[100];
                //將套接字獲取到的位元組陣列轉換為人可以看懂的字串
                string str = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);//從終端傳過來的資訊
                Console.WriteLine("傳輸的字元為：{0}", str);

                //將輸入的內容字串轉換為機器可以識別的位元組陣列
                string result="hello word";//發回給終端的資訊
                arrClientSendResult = Encoding.UTF8.GetBytes(result);
                }
               
                e.SetBuffer(arrClientSendResult, 0, arrClientSendResult.Length);

                bool willRaiseEvent = token.Socket.SendAsync(e);
                if (!willRaiseEvent)
                {
                    ProcessSend(e);
                }

            }
            else
            {
                CloseClientSocket(e);
            }
        }

        // This method is invoked when an asynchronous send operation completes.  
        // The method issues another receive on the socket to read any additional 
        // data sent from the client
        //
        // <param name="e"></param>
        private void ProcessSend(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)
            {
                // done echoing data back to the client
                AsyncUserToken token = (AsyncUserToken)e.UserToken;
                // read the next block of data send from the client
                m_bufferManager.FreeBuffer(e);//將快取釋放
                m_bufferManager.SetBuffer(e);//重新設定快取。如不進行這兩步操作，則下一次發過來的資訊將在上次的快取基礎上進行儲存導致資訊換亂
                bool willRaiseEvent = token.Socket.ReceiveAsync(e);
                if (!willRaiseEvent)
                {
                    ProcessReceive(e);
                }
            }
            else
            {
                CloseClientSocket(e);
            }
        }

        private void CloseClientSocket(SocketAsyncEventArgs e)
        {
            AsyncUserToken token = e.UserToken as AsyncUserToken;

            // close the socket associated with the client
            try
            {
                token.Socket.Shutdown(SocketShutdown.Send);
            }
            // throws if client process has already closed
            catch (Exception) { }
            token.Socket.Close();

            // decrement the counter keeping track of the total number of clients connected to the server
            Interlocked.Decrement(ref m_numConnectedSockets);
            m_maxNumberAcceptedClients.Release();
            Console.WriteLine("A client has been disconnected from the server. There are {0} clients connected to the server", m_numConnectedSockets);

            // Free the SocketAsyncEventArg so they can be reused by another client
            m_readWritePool.Push(e);
        }

    }    
}
 

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

namespace IOCPServer
{
    class AsyncUserToken
    {
        Socket m_socket;

        public AsyncUserToken() : this(null) { }

        public AsyncUserToken(Socket socket)
        {
            m_socket = socket;
        }

        public Socket Socket
        {
            get { return m_socket; }
            set { m_socket = value; }
        }
    }
}
 

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

namespace IOCPServer
{
    class BufferManager
    {
        int m_numBytes;                 // the total number of bytes controlled by the buffer pool
        byte[] m_buffer;                // the underlying byte array maintained by the Buffer Manager
        Stack<int> m_freeIndexPool;     // 
        int m_currentIndex;
        int m_bufferSize;

        public BufferManager(int totalBytes, int bufferSize)
        {
            m_numBytes = totalBytes;
            m_currentIndex = 0;
            m_bufferSize = bufferSize;
            m_freeIndexPool = new Stack<int>();
        }

        // Allocates buffer space used by the buffer pool
        public void InitBuffer()
        {
            // create one big large buffer and divide that 
            // out to each SocketAsyncEventArg object
            m_buffer = new byte[m_numBytes];
        }

        // Assigns a buffer from the buffer pool to the 
        // specified SocketAsyncEventArgs object
        //
        // <returns>true if the buffer was successfully set, else false</returns>
        public bool SetBuffer(SocketAsyncEventArgs args)
        {

            if (m_freeIndexPool.Count > 0)
            {
                args.SetBuffer(m_buffer, m_freeIndexPool.Pop(), m_bufferSize);
            }
            else
            {
                if ((m_numBytes - m_bufferSize) < m_currentIndex)
                {
                    return false;
                }
                args.SetBuffer(m_buffer, m_currentIndex, m_bufferSize);
                m_currentIndex += m_bufferSize;
            }
            return true;
        }

        // Removes the buffer from a SocketAsyncEventArg object.  
        // This frees the buffer back to the buffer pool
        public void FreeBuffer(SocketAsyncEventArgs args)
        {
            m_freeIndexPool.Push(args.Offset);
            args.SetBuffer(null, 0, 0);
        }

    }
}
 

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

namespace IOCPServer
{
    class SocketAsyncEventArgsPool
    {
        Stack<SocketAsyncEventArgs> m_pool;

        // Initializes the object pool to the specified size
        //
        // The "capacity" parameter is the maximum number of 
        // SocketAsyncEventArgs objects the pool can hold
        public SocketAsyncEventArgsPool(int capacity)
        {
            m_pool = new Stack<SocketAsyncEventArgs>(capacity);
        }

        // Add a SocketAsyncEventArg instance to the pool
        //
        //The "item" parameter is the SocketAsyncEventArgs instance 
        // to add to the pool
        public void Push(SocketAsyncEventArgs item)
        {
            if (item == null) { throw new ArgumentNullException("Items added to a SocketAsyncEventArgsPool cannot be null"); }
            lock (m_pool)
            {
                m_pool.Push(item);
            }
        }

        // Removes a SocketAsyncEventArgs instance from the pool
        // and returns the object removed from the pool
        public SocketAsyncEventArgs Pop()
        {
            lock (m_pool)
            {
                return m_pool.Pop();
            }
        }

        // The number of SocketAsyncEventArgs instances in the pool
        public int Count
        {
            get { return m_pool.Count; }
        }

    }
}

 Server server = new Server(5,10000);
            server.Init();
            IPAddress ip = IPAddress.Parse("127.0.0.1");
            IPEndPoint ipe = new IPEndPoint(ip, 11);
            server.Start(ipe);