C# Network Programming Series Articles (6) Socket Implements Synchronous UDP Server

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;
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. Following the explanation below, you will find that using the Socket class to develop Windows network applications actually has There are rules to be found, and they follow roughly the same steps in most cases.

#This section introduces the use of Socket to implement a synchronous UDP server.

Socket synchronization UDP server

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

namespace NetFrame.Net.UDP.Sock.Synchronous
{
    /// <summary>
    /// Socket 实现同步UDP服务器
    /// </summary>
    public class SocketUDPServer
    {
        #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<SocketUDPState> _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 SocketUDPServer(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 SocketUDPServer(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 SocketUDPServer(IPAddress localIPAddress, int listenPort, int maxClient)
        {
            this.Address = localIPAddress;
            this.Port = listenPort;
            this.Encoding = Encoding.Default;

            _maxClient = maxClient;
            _clients = new List<SocketUDPState>();
            _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));
                //启动一个线程监听数据
                new Thread(ReceiveData).Start();
            }
        }

        /// <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
                CloseAllClient();
            }
        }

        /// <summary>
        /// 同步数据接收方法
        /// </summary>
        private void ReceiveData()
        {
            int len = -1;
            EndPoint remote = null;
            while (true)
            {
                try
                {
                    len = _serverSock.ReceiveFrom(_recvBuffer, ref remote);

                    //if (!_clients.Contains(remote))
                    //{
                    //    _clients.Add(remote);
                    //}
                }
                catch (Exception)
                {
                    //TODO 异常处理操作
                    RaiseOtherException(null);
                }
            }
        }
        /// <summary>
        /// 同步发送数据
        /// </summary>
        public void Send(string msg, EndPoint clientip)
        {
            byte[] data = Encoding.Default.GetBytes(msg);
            try
            {
                _serverSock.SendTo(data, clientip);
                //数据发送完成事件
                RaiseCompletedSend(null);
            }
            catch (Exception)
            {
                //TODO 异常处理
                RaiseOtherException(null);
            }
        }

        #endregion

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

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

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

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

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

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

Customer status encapsulation class

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

namespace NetFrame.Net.UDP.Sock.Synchronous
{
    public class SocketUDPState
    {
        // 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);
    }
}

Server event parameter class

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

namespace NetFrame.Net.UDP.Sock.Synchronous
{
    /// <summary>
    /// Socket实现同步UDP服务器
    /// </summary>
    public class SocketUDPEventArgs:EventArgs
    {
        /// <summary>
        /// 提示信息
        /// </summary>
        public string _msg;

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

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

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

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