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异步Socket服务器与客户端

本文灵感来自Andre Azevedo 在CodeProject上面的一片文章，An Asynchronous Socket Server and Client，讲的是异步的Socket通信。

Socket连接(Socket Connection)
Socket服务(Socket Service)
连接主机(Connection Host)

加密与压缩(Encrypt与Compress)
请求入队(Enqueuing Requests)
确保发送和接收(Ensure send and recieve)
检查消息头(Check message header)
检查空闲连接(Checking idle connections)
加密服务

SSL认证(SSL authentication)
对称认证(Symmetric authentication)
连接创建者(Connection Creator)
Socket服务器与Socket侦听者(SocketServer and SocketListener)

Socket服务器构造函数与方法(SocketServer constructor and methods)
Socket客户端与Socket连接者(SocketClient and SocketConnector)

Socket客户端构造函数与方法(SocketClient constructor and methods)
应答演示项目(Echo Demo Project)

主机(Hosts)
服务(Services)
结语(Conclusion)
版本历史(History)

本文仅实现一个相对简单的异步Socket服务器与客户端通信示例。

首先需要说明如下2个问题

1.同步、异步、多线程是什么关系？答：同步是等待返回，相当于阻塞式；异步是不等待返回，是非阻塞式，可以用多线程实现。

2.有些异步方法有两种实现方式, 如BeginAccept()和AcceptAsync(), 这两个方法有什么区别呢?答：以 Begin 和 End 开头的方法是以 APM(Asynchronous Programming Model)设计方法实现的异步操作, 以 Async 结尾的方法是利用称为 EAP (Event-based Asynchronous Pattern) 的设计方法实现的异步操作。

界面简单如下：

主要代码如下：

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
 
namespace Chatting
{
    public abstract class SocketFunc
    {
        //不管是服务端还是客户端, 建立连接后用这个Socket进行通信
        public Socket communicateSocket = null;
 
        //服务端和客户端建立连接的方式稍有不同, 子类会重载
        public abstract void Access(string IP, System.Action AccessAciton);
 
        //发送消息的函数
        public void Send(string message)
        {
            if (communicateSocket.Connected == false)
            {
                throw new Exception("还没有建立连接, 不能发送消息");
            }
            Byte[] msg = Encoding.UTF8.GetBytes(message);
            communicateSocket.BeginSend(msg,0, msg.Length, SocketFlags.None,
                ar => {
                 
                }, null);
        }
 
        //接受消息的函数
        public void Receive(System.Action<string> ReceiveAction)
        {
            //如果消息超过1024个字节, 收到的消息会分为(总字节长度/1024 +1)条显示
            Byte[] msg = new byte[1024];
            //异步的接受消息
            communicateSocket.BeginReceive(msg, 0, msg.Length, SocketFlags.None,
                ar => {
                    //对方断开连接时, 这里抛出Socket Exception
                    //An existing connection was forcibly closed by the remote host 
                        communicateSocket.EndReceive(ar); 
                    ReceiveAction(Encoding.UTF8.GetString(msg).Trim('',' '));
                    Receive(ReceiveAction);
                }, null);
        }
    }
 
 
    public class ServerSocket:SocketFunc
    {
        //服务端重载Access函数
        public override void Access(string IP, System.Action AccessAciton)
        {
            Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            //本机预使用的IP和端口
            IPEndPoint serverIP = new IPEndPoint(IPAddress.Any, 9050);
            //绑定服务端设置的IP
            serverSocket.Bind(serverIP);
            //设置监听个数
            serverSocket.Listen(1);
            //异步接收连接请求
            serverSocket.BeginAccept(ar =>
                {
                    base.communicateSocket = serverSocket.EndAccept(ar);
                    AccessAciton();
                }, null);
        }
    }
 
    public class ClientSocket:SocketFunc
    {
        //客户端重载Access函数
        public override void Access(string IP, System.Action AccessAciton)
        {
            base.communicateSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            base.communicateSocket.Bind(new IPEndPoint(IPAddress.Any, 9051));
             
            //服务器的IP和端口
            IPEndPoint serverIP;
            try
            {
                serverIP = new IPEndPoint(IPAddress.Parse(IP), 9050);
            }
            catch
            {
                throw new Exception(String.Format("{0}不是一个有效的IP地址!", IP));
            }
             
            //客户端只用来向指定的服务器发送信息,不需要绑定本机的IP和端口,不需要监听
            try
            {
                base.communicateSocket.BeginConnect(serverIP, ar =>
                {
                    AccessAciton();
                }, null);
            }
            catch
            {
                throw new Exception(string.Format("尝试连接{0}不成功!", IP));
            }
        }
    }
}