自定义协议

每次编写设计网络通讯程序时，总面对一个问题，就是要自定义一组应用协议（即通讯协议），然后再写相应的方法来解析协议，并提供相应的接口供上层调用。如果只是简单的文本信息通讯还容易，但要交换一些控制信息或结构复杂的数据时，比如做联机游戏，更是让人头疼。

最近突然想到一个点子，可以用对象串行化技术将对象直接转换为二进制数据发送，然后接收时直接还原为对象。具体过程是，将要发送的数据放在一个HashTable中，串行化后发送出去，在接收方接收到数据并还原为HashTable，根据预先约定好的Key和获取自己关心的数据。在这种情况下，定义通讯协议的内容实质上也就只是指定一组Key就行了。再也不用做那些规定第几个字段是什么类型有多长的烦躁的事情了。

可能很多人很善于用XML，也将之广泛用于网络通讯。XML有不可比拟的好处，因为它是同平台无关的，而且基本上任何开发语言都有现成库来解析XML。这个和我的观点并不冲突。对象串行化并不局限于二进制数据。C#里有丰富的方法，可以将对象串行化为XML文档，也支持用SOAP协议来串行化数据。所以只要用公共的串行化标准来串行化对象，也可以达到跨平台、跨语言的目的。其实现在流行的Web Service其核心技术也就大概是这样吧。

原理说完了，贴段代码做个例子。ObjectTransferClient（简称OTC）是一个利用UDP协议及二进制对象串行化的包括对象发送和接收的库。调用方法很简单，用Send发送对象，响应ReceiveObject事件来处理接收的对象。至于具体细节就不多叙述了，相信有一定C#基础的人能轻松看懂的。

这一原理的应用潜力是巨大的，我在这里抛砖引玉，还请指教。

using System;

using System.Net.Sockets;

using System.Net;

using System.Runtime.Serialization.Formatters.Binary;

using System.Threading;

namespace OTC

{

         /// <summary>

         /// 对象传送器，使用UDP协议通过网路在不同主机间传送对象。

         /// </summary>

         public class ObjectTransferClient : IDisposable

         {

                   private Thread ListenThread;

                   private BinaryFormatter Serializer = new BinaryFormatter();

                   private int m_Port;

                   private UdpClient m_Client;

                   private bool m_IsStart;

                   private bool m_IsConnected;

                   /// <summary>

                   /// 接收到对象事件

                   /// </summary>

                   public event ReceiveObjectEventHandler ReceiveObject;

                   /// <summary>

                   /// 构建一个对象传送器，默认端口7321

                   /// </summary>

                   public ObjectTransferClient() : this(7321)

                   {

                   //

                   // TODO: 在此处添加构造函数逻辑

                   //

                   }

                   /// <summary>

                   /// 指定端口号构建一个对象传送器。

                   /// </summary>

                  /// <param name="port">端口号</param>

                   public ObjectTransferClient(int port)

                   {

                            this.m_Port = port;

                            this.m_IsConnected = false;

                            this.m_IsStart = false;

                   }

                   /// <summary>

                   /// 初始化传送器并开始工作

                   /// </summary>

                   public void Start()

                   {

                            if (!this.m_IsStart)

                            {

                                     this.m_Client = new UdpClient(this.m_Port);

                                     ListenThread = new Thread(new ThreadStart(this.Listen));

                                     ListenThread.Start();

                                     this.m_IsStart = true;

                            }

                   }

                   /// <summary>

                   /// 使用指定的主机名和端口连接默认的远程主机

                   /// </summary>

                   /// <param name="hostname">主机名</param>

                   /// <param name="port">端口</param>

                   public void Connect(string hostname, int port)

                   {

                            this.m_Client.Connect(hostname, port);

                   }

                   /// <summary>

                   /// 使用指定的IP地址和端口连接默认的远程主机

                   /// </summary>

                   /// <param name="ipaddress">IP地址</param>

                   /// <param name="port">端口</param>

                   public void Connect(IPAddress ipaddress, int port)

                   {

                            this.m_Client.Connect(ipaddress, port);

                   }

                   /// <summary>

                   /// 使用网络终结点连接默认的远程主机

                   /// </summary>

                   /// <param name="iep">网络端点</param>

                   public void Connect(IPEndPoint iep)

                   {

                            this.m_Client.Connect(iep);

                   }

                   private byte[] CreateArgPackage(object obj)

                   {

                            IPEndPoint local = new IPEndPoint(IPAddress.Any, this.m_Port);

                            System.IO.MemoryStream outStream = new System.IO.MemoryStream();

                            this.Serializer.Serialize(outStream, new ReceiveObjectEventArgs(obj, local));

                            return outStream.ToArray();

                   }

                   /// <summary>

                   /// 将对象发送到默认主机。调用此方法前必须先调用Connect方法连接默认主机。

                   /// </summary>

                   /// <param name="obj">要发送的对象</param>

                   public void Send(object obj)

                   {

                            if (this.IsConnected)

                            {

                                     byte[] data = this.CreateArgPackage(obj);

                                     this.m_Client.Send(data, data.Length);

                            }

                            else

                            {

                                     throw new Exception("必须先连接默认主机");

                            }

                   }

                   /// <summary>

                   /// 将对象发送到指定的主机。若调用了Connect方法连接了默认主机，则此方法不可用。

                   /// </summary>

                   /// <param name="obj">要发送的对象</param>

                   /// <param name="remoteIEP">目标主机的网络端点</param>

                   public void Send(object obj, IPEndPoint remoteIEP)

                   {

                            if (this.IsConnected)

                            {

                                     throw new Exception("已经连接了默认主机");

                            }

                            else

                            {

                                     byte[] data = this.CreateArgPackage(obj);

                                     this.m_Client.Send(data, data.Length, remoteIEP);

                            }

                   }

                   /// <summary>

                   /// 监听接收数据线程方法

                   /// </summary>

                   protected void Listen()

                   {

                            BinaryFormatter Serializer = new BinaryFormatter();

                            IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);

                            while (true)

                            {

                                     try

                                     {

                                               object revobj = Serializer.Deserialize(new System.IO.MemoryStream(m_Client.Receive(ref RemoteIpEndPoint)));

                                               ReceiveObjectEventArgs revarg = (ReceiveObjectEventArgs)revobj;

                                               RemoteIpEndPoint.Port = revarg.RemoteIEP.Port;

                                               revarg.RemoteIEP = RemoteIpEndPoint;

                                               if (this.ReceiveObject != null)

                                               {

                                                        this.ReceiveObject(this, revarg);

                                               }

                                     }

                                     catch

                                     {

                                               break;

                                     }

                            }

                   }

                   #region 公共属性区

                   /// <summary>

                   /// 返回或设置接收对象的端口号

                   /// </summary>

                   public int Port

                   {

                            get

                            {

                                     return this.m_Port;

                            }

                            set

                            {

                                     this.m_Port = value;

                            }

                   }

                   /// <summary>

                   /// 返回对象发送器是否已经初始化并开始工作

                   /// </summary>

                   public bool IsStart

                   {

                            get

                            {

                                     return this.m_IsStart;

                            }

                   }

                   /// <summary>

                   /// 返回对象发送器是否已经连接默认远程主机

                   /// </summary>

                   public bool IsConnected

                   {

                            get

                            {

                                     return this.m_IsConnected;

                            }

                   }

                   #endregion

                   #region IDisposable 成员

                   public void Dispose()

                   {

                            // TODO:  添加 ObjectTransferClient.Dispose 实现

                            this.m_Client.Close();

                            this.ListenThread.Abort();

                   }

                   #endregion

         }

 

         /// <summary>

         /// 接收对象事件参数

         /// </summary>

         [Serializable]

         public class ReceiveObjectEventArgs : EventArgs

         {

                   private object _obj;

                   private System.Net.IPEndPoint _iep;

                   /// <summary>

                   /// 构建一个接收对象事件的参数

                   /// </summary>

                   /// <param name="obj">接收到的对象</param>

                   /// <param name="iep">发送者的网络端点</param>

                   internal ReceiveObjectEventArgs(object obj, System.Net.IPEndPoint iep)

                   {

                            this._obj = obj;

                            this._iep = iep;

                   }

                   /// <summary>

                   /// 构建一个空的接收对象事件参数

                   /// </summary>

                   public ReceiveObjectEventArgs():this(null, null)

                   {

                   }

                   /// <summary>

                   /// 接收到的对象

                   /// </summary>

                   public object Obj

                   {

                            get

                            {

                                     return this._obj;

                            }

                   }

                   /// <summary>

                   /// 发送方的网络端点

                   /// </summary>

                   public System.Net.IPEndPoint RemoteIEP

                   {

                            get

                            {

                                     return this._iep;

                            }

                            set

                            {

                                     this._iep = value;

                            }

                   }

         }

 

         /// <summary>

         /// 接收对象事件的委托

         /// </summary>

         public delegate void ReceiveObjectEventHandler(object sender, ReceiveObjectEventArgs e);

}