Introduction to this article

In .Net, the System.Net.Sockets namespace provides a managed implementation of the Windows Sockets (Winsock) interface for developers who need to tightly control network access. All other network access classes in the System.Net namespace are built on this socket implementation. The TCPClient, TCPListener, and UDPClient classes encapsulate detailed information about creating TCP and UDP connections to the Internet; the NetworkStream class provides For the basic data flow of network access, Socket can be seen in many common Internet services, such as Telnet, HTTP, Email, Echo, etc. Although these services have different definitions of communication protocols, their basic transmission uses Socket. In fact, Socket can be regarded as a data channel like a Stream. This channel is established between the application (client) and the remote server. Then, the reading (receiving) and writing (sending) of data are both for through this channel.
It can be seen that after creating a Socket object on the application side or server side, you can use the Send/SentTo method to send data to the connected Socket, or use the Receive/ReceiveFrom method to receive data from the connected Socket. Data;
For Socket programming, the .NET Framework's Socket class is a managed code version of the socket service provided by the Winsock32 API. There are a number of methods provided for implementing network programming, and in most cases the Socket class methods simply marshal the data to their native Win32 copies and handle any necessary security checks. If you are familiar with Winsock API functions, it will be very easy to use the Socket class to write network programs. Of course, if you have never been exposed to it, it will not be too difficult. Follow the explanation below and you will find that using the Socket class to develop windows There are rules for web applications, and they follow roughly the same steps in most cases.

This section introduces the use of Socket to implement a high-performance asynchronous UDP server. In fact, UDP does not distinguish between clients and servers. , but sometimes we communicate with the server using UDP.

Socket Asynchronous UDP Server

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

namespace NetFrame.Net.UDP.Sock.Asynchronous
{
    /// <summary>
    /// SOCKET实现异步UDP服务器
    /// </summary>
    public class AsyncSocketUDPServer
    {
        #region Fields
        /// <summary>
        /// 服务器程序允许的最大客户端连接数
        /// </summary>
        private int _maxClient;

        /// <summary>
        /// 当前的连接的客户端数
        /// </summary>
        //private int _clientCount;

        /// <summary>
        /// 服务器使用的同步socket
        /// </summary>
        private Socket _serverSock;

        /// <summary>
        /// 客户端会话列表
        /// </summary>
        //private List<AsyncUDPSocketState> _clients;

        private bool disposed = false;

        /// <summary>
        /// 数据接受缓冲区
        /// </summary>
        private byte[] _recvBuffer;

        #endregion

        #region Properties

        /// <summary>
        /// 服务器是否正在运行
        /// </summary>
        public bool IsRunning { get; private set; }
        /// <summary>
        /// 监听的IP地址
        /// </summary>
        public IPAddress Address { get; private set; }
        /// <summary>
        /// 监听的端口
        /// </summary>
        public int Port { get; private set; }
        /// <summary>
        /// 通信使用的编码
        /// </summary>
        public Encoding Encoding { get; set; }

        #endregion

        #region 构造函数

        /// <summary>
        /// 异步Socket UDP服务器
        /// </summary>
        /// <param name="listenPort">监听的端口</param>
        public AsyncSocketUDPServer(int listenPort)
            : this(IPAddress.Any, listenPort,1024)
        {
        }

        /// <summary>
        /// 异步Socket UDP服务器
        /// </summary>
        /// <param name="localEP">监听的终结点</param>
        public AsyncSocketUDPServer(IPEndPoint localEP)
            : this(localEP.Address, localEP.Port,1024)
        {
        }

        /// <summary>
        /// 异步Socket UDP服务器
        /// </summary>
        /// <param name="localIPAddress">监听的IP地址</param>
        /// <param name="listenPort">监听的端口</param>
        /// <param name="maxClient">最大客户端数量</param>
        public AsyncSocketUDPServer(IPAddress localIPAddress, int listenPort, int maxClient)
        {
            this.Address = localIPAddress;
            this.Port = listenPort;
            this.Encoding = Encoding.Default;

            _maxClient = maxClient;
            //_clients = new List<AsyncUDPSocketState>();
            _serverSock = new Socket(localIPAddress.AddressFamily, SocketType.Dgram, ProtocolType.Udp);

            _recvBuffer=new byte[_serverSock.ReceiveBufferSize];
        }

        #endregion

        #region Method
        /// <summary>
        /// 启动服务器
        /// </summary>
        /// <returns>异步TCP服务器</returns>
        public void Start()
        {
            if (!IsRunning)
            {
                IsRunning = true;
                _serverSock.Bind(new IPEndPoint(this.Address, this.Port));
                //_serverSock.Connect(new IPEndPoint(IPAddress.Any, 0));

                AsyncSocketUDPState so = new AsyncSocketUDPState();
                so.workSocket = _serverSock;

                _serverSock.BeginReceiveFrom(so.buffer, 0, so.buffer.Length, SocketFlags.None,
                    ref so.remote, new AsyncCallback(ReceiveDataAsync), null);


                //EndPoint sender = new IPEndPoint(IPAddress.Any, 0);

                //_serverSock.BeginReceiveFrom(_recvBuffer, 0, _recvBuffer.Length, SocketFlags.None,
                //    ref sender, new AsyncCallback(ReceiveDataAsync), sender);

                //BeginReceive 和 BeginReceiveFrom的区别是什么
                /*_serverSock.BeginReceive(_recvBuffer, 0, _recvBuffer.Length, SocketFlags.None,
                    new AsyncCallback(ReceiveDataAsync), null);*/
            }
        }

        /// <summary>
        /// 停止服务器
        /// </summary>
        public void Stop()
        {
            if (IsRunning)
            {
                IsRunning = false;
                _serverSock.Close();
                //TODO 关闭对所有客户端的连接

            }
        }

        /// <summary>
        /// 接收数据的方法
        /// </summary>
        /// <param name="ar"></param>
        private void ReceiveDataAsync(IAsyncResult ar)
        {
            AsyncSocketUDPState so = ar.AsyncState as AsyncSocketUDPState;
            //EndPoint sender = new IPEndPoint(IPAddress.Any, 0);
            int len = -1;
            try
            {
                len = _serverSock.EndReceiveFrom(ar, ref so.remote);

                //len = _serverSock.EndReceiveFrom(ar, ref sender);

                //EndReceiveFrom 和 EndReceive区别
                //len = _serverSock.EndReceive(ar);
                //TODO 处理数据

                //触发数据收到事件
                RaiseDataReceived(so);
            }
            catch (Exception)
            {
                //TODO 处理异常
                RaiseOtherException(so);
            }
            finally
            {
                if (IsRunning && _serverSock != null)
                    _serverSock.BeginReceiveFrom(so.buffer, 0, so.buffer.Length, SocketFlags.None,
                ref so.remote, new AsyncCallback(ReceiveDataAsync), so);
            }
        }
        /// <summary>
        /// 发送数据
        /// </summary>
        /// <param name="msg"></param>
        /// <param name="remote"></param>
        public void Send(string msg,EndPoint remote)
        {
            byte[] data = Encoding.Default.GetBytes(msg);
            try
            {
                RaisePrepareSend(null);
                _serverSock.BeginSendTo(data, 0, data.Length, SocketFlags.None, remote, new AsyncCallback(SendDataEnd), _serverSock);
            }
            catch (Exception)
            {
                //TODO 异常处理
                RaiseOtherException(null);
            }
        }

        private void SendDataEnd(IAsyncResult ar)
        {
            ((Socket)ar.AsyncState).EndSendTo(ar);
            RaiseCompletedSend(null);
        }

        #endregion

        #region 事件
        /// <summary>
        /// 接收到数据事件
        /// </summary>
        public event EventHandler<AsyncSocketUDPEventArgs> DataReceived;

        private void RaiseDataReceived(AsyncSocketUDPState state)
        {
            if (DataReceived != null)
            {
                DataReceived(this, new AsyncSocketUDPEventArgs(state));
            }
        }

        /// <summary>
        /// 发送数据前的事件
        /// </summary>
        public event EventHandler<AsyncSocketUDPEventArgs> PrepareSend;

        /// <summary>
        /// 触发发送数据前的事件
        /// </summary>
        /// <param name="state"></param>
        private void RaisePrepareSend(AsyncSocketUDPState state)
        {
            if (PrepareSend != null)
            {
                PrepareSend(this, new AsyncSocketUDPEventArgs(state));
            }
        }

        /// <summary>
        /// 数据发送完毕事件
        /// </summary>
        public event EventHandler<AsyncSocketUDPEventArgs> CompletedSend;

        /// <summary>
        /// 触发数据发送完毕的事件
        /// </summary>
        /// <param name="state"></param>
        private void RaiseCompletedSend(AsyncSocketUDPState state)
        {
            if (CompletedSend != null)
            {
                CompletedSend(this, new AsyncSocketUDPEventArgs(state));
            }
        }

        /// <summary>
        /// 网络错误事件
        /// </summary>
        public event EventHandler<AsyncSocketUDPEventArgs> NetError;
        /// <summary>
        /// 触发网络错误事件
        /// </summary>
        /// <param name="state"></param>
        private void RaiseNetError(AsyncSocketUDPState state)
        {
            if (NetError != null)
            {
                NetError(this, new AsyncSocketUDPEventArgs(state));
            }
        }

        /// <summary>
        /// 异常事件
        /// </summary>
        public event EventHandler<AsyncSocketUDPEventArgs> OtherException;
        /// <summary>
        /// 触发异常事件
        /// </summary>
        /// <param name="state"></param>
        private void RaiseOtherException(AsyncSocketUDPState state, string descrip)
        {
            if (OtherException != null)
            {
                OtherException(this, new AsyncSocketUDPEventArgs(descrip, state));
            }
        }
        private void RaiseOtherException(AsyncSocketUDPState state)
        {
            RaiseOtherException(state, "");
        }
        #endregion

        #region Close
        /// <summary>
        /// 关闭一个与客户端之间的会话
        /// </summary>
        /// <param name="state">需要关闭的客户端会话对象</param>
        public void Close(AsyncSocketUDPState state)
        {
            if (state != null)
            {
                //_clients.Remove(state);
                //_clientCount--;
                //TODO 触发关闭事件
            }
        }
        /// <summary>
        /// 关闭所有的客户端会话,与所有的客户端连接会断开
        /// </summary>
        public void CloseAllClient()
        {
            //foreach (AsyncUDPSocketState client in _clients)
            //{
            //    Close(client);
            //}
            //_clientCount = 0;
            //_clients.Clear();
        }

        #endregion

        #region 释放
        /// <summary>
        /// Performs application-defined tasks associated with freeing, 
        /// releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources
        /// </summary>
        /// <param name="disposing"><c>true</c> to release 
        /// both managed and unmanaged resources; <c>false</c> 
        /// to release only unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    try
                    {
                        Stop();
                        if (_serverSock != null)
                        {
                            _serverSock = null;
                        }
                    }
                    catch (SocketException)
                    {
                        //TODO
                        RaiseOtherException(null);
                    }
                }
                disposed = true;
            }
        }
        #endregion
    }
}

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Session Encapsulation Class

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

namespace NetFrame.Net.UDP.Sock.Asynchronous
{
    public class AsyncSocketUDPState
    {
        // 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 EndPoint remote = new IPEndPoint(IPAddress.Any, 0);
    }
}

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Socket Asynchronous UDP Server Event Parameter Class

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

namespace NetFrame.Net.UDP.Sock.Asynchronous
{
    /// <summary>
    /// SOCKET 异步UDP 事件类
    /// </summary>
    public class AsyncSocketUDPEventArgs : EventArgs
    {
        /// <summary>
        /// 提示信息
        /// </summary>
        public string _msg;

        /// <summary>
        /// 客户端状态封装类
        /// </summary>
        public AsyncSocketUDPState _state;

        /// <summary>
        /// 是否已经处理过了
        /// </summary>
        public bool IsHandled { get; set; }

        public AsyncSocketUDPEventArgs(string msg)
        {
            this._msg = msg;
            IsHandled = false;
        }
        public AsyncSocketUDPEventArgs(AsyncSocketUDPState state)
        {
            this._state = state;
            IsHandled = false;
        }
        public AsyncSocketUDPEventArgs(string msg, AsyncSocketUDPState state)
        {
            this._msg = msg;
            this._state = state;
            IsHandled = false;
        }
    }
}

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