主题列表：
COMET彗星（一）SERVER PUSH介绍
COMET彗星（二）基于SERVER PUSH的消息传输
引言：
在上一篇随笔中，对COMET使用的类和作用进行了简短的介绍，从本篇随笔开始，将从实体类开始，对COMET的核心进行构建分析。
CORE框架：
图1.1 COMET核心框架
CometMessage类：
CometMessage类是COMET的通信载体，对消息的主体进行抽象，实际上这个类是最容易进行扩展的，因为从设计上看，它只是一个消息的容器。而诸如地理坐标，业务数据等，都可以通过这个类来进行直接扩充。
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.Serialization; namespace MethodWorx.AspNetComet.Core { /// <summary> /// CometMessage Class /// /// This is a CometMessage that has been sent to the client, the DataContract names have been /// shortened to remove any bytes we dont need from the message (ok, did'nt save much, but we can do it!) /// </summary> [DataContract(Name="cm")] public class CometMessage { [DataMember(Name="mid")] private long messageId; [DataMember(Name="n")] private string name; [DataMember(Name="c")] private object contents; /// <summary> /// Gets or Sets the MessageId, used to track which message the Client last received /// </summary> public long MessageId { get { return this.messageId; } set { this.messageId = value; } } /// <summary> /// Gets or Sets the Content of the Message /// </summary> public object Contents { get { return this.contents; } set { this.contents = value; } } /// <summary> /// Gets or Sets the error message if this is a failure /// </summary> public string Name { get { return this.name; } set { this.name = value; } } } }
类的设计简单明了，这里有必要解释下使用System.Runtime.Serialization命名空间的意义。
“System.Runtime.Serialization 命名空间包含可用于将对象序列化和反序列化的类。序列化是将对象或对象图形转换为线性字节序列，以存储或传输到另一个位置的过程。反序列化是接受存储的信息并利用它重新创建对象的过程。”
这是MSDN给我们的解释，将对象转变为线性字节，然后方便传输与调用。当然这个例子中的数据类型并不复杂，但也包含了LONG，OBJECT，STRING这样的数据类型。其中Contents成员为object对象，这给我们留下了非常大的想像空间。（图片？复杂对象类型？自定义对象类型？……）
CometClient类：
CometClient类是对客户端信息的抽象类，同时包含了两个关键属性ConnectionIdleSeconds和ConnectionTimeoutSeconds。由于考虑到不同客户端间传递属性，仍然使用System.Runtime.Serialization来序列化信息。
关于JSON的应用，这个框架其实也提供了相应支持。后面的随笔中我会介绍。
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.Serialization; namespace MethodWorx.AspNetComet.Core { /// <summary> /// CometClient Class /// /// This represents a logged in client within the COMET application. This marked as a DataContract becuase /// it can be seralized to the client using JSON /// </summary> [DataContract] public class CometClient { [DataMember] private string privateToken; [DataMember] private string publicToken; [DataMember] private string displayName; [DataMember] private DateTime lastActivity; [DataMember] private int connectionIdleSeconds; [DataMember] private int connectionTimeoutSeconds; /// <summary> /// Gets or Sets the token used to identify the client to themselves /// </summary> public string PrivateToken { get { return this.privateToken; } set { this.privateToken = value; } } /// <summary> /// Gets or Sets the token used to identify the client to other clients /// </summary> public string PublicToken { get { return this.publicToken; } set { this.publicToken = value; } } /// <summary> /// Gets or Sets the display name of the client /// </summary> public string DisplayName { get { return this.displayName; } set { this.displayName = value; } } /// <summary> /// Gets or Sets the last activity of the client /// </summary> public DateTime LastActivity { get { return this.lastActivity; } set { this.lastActivity = value; } } /// <summary> /// Gets or Sets the ConnectionIdleSections property which is the number of seconds a connection will remain /// alive for without being connected to a client, after this time has expired the client will /// be removed from the state manager /// </summary> public int ConnectionIdleSeconds { get { return this.connectionIdleSeconds; } set { this.connectionIdleSeconds = value; } } /// <summary> /// Gets or Sets the ConnectionTimeOutSections property which is the number of seconds a connection will remain /// alive for whilst being connected to a client, but without receiving any messages. After a timeout has expired /// A client should restablish a connection to the server /// </summary> public int ConnectionTimeoutSeconds { get { return this.connectionTimeoutSeconds; } set { this.connectionTimeoutSeconds = value; } } } }
ConnectionIdleSeconds：用来设置连接线程，当connection断线后，后台Thread的存活时间。
ConnectionTimeoutSeconds：客户端的超时时间，当超过时间后，客户端重新连接服务器。
ps:有这两个属性后，基本上完成了客户端连接的控制，超时重连接，无连接时杀死后台线程。
ICometStateProvider接口：
ICometStateProvider接口直接被CometStateMessager建立，这样的好处是实例化CometStateMessager对象后，CometStateMessager对象可以直接调用ICometStateProvider接口的实现，实际上实现了Adapter的方式，我们可以定制不同的InProcCometStateProvider类（在下面会提到）来定制自己的接口。
ICometStateProvider接口类提供了如下几个接口。
InitializeClient:提供ComentClient的初始化操作。
GetMessages:得到一个Messages的消息队列。
SendMessage:发送Message数据。
SendMessage:可以针对Client name来进行消息发布（私人会话）。
GetCometClient:返回一个Client。
KillIdleCometClient:杀掉一个无效的Client对象。
ps:当然这个接口是可以被拓展的，而且实现起来非常简单。得到Client队列信息，得到Client状态等等。甚至你可以想象一些更复杂的应用（比如加入一个流媒体消息……）。
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace MethodWorx.AspNetComet.Core { /// <summary> /// This interface can be implemented to provide a custom state provider /// for the CometStateManager class. Typical examples may be using SqlServer /// to enable the operation over a server farm /// </summary> public interface ICometStateProvider { /// <summary> /// Implementation of this method should store the cometClient instance in some sort /// of cache (eg Memory, Db etc..) /// </summary> /// <param name="cometClient"></param> void InitializeClient(CometClient cometClient); /// <summary> /// Imeplementation of this method should return all the messages that are queued /// for a specific client, it is only interested in messages that have a greater id than /// lastMessageId /// </summary> /// <param name="clientPrivateToken"></param> /// <param name="lastMessageId"></param> /// <returns></returns> CometMessage[] GetMessages(string clientPrivateToken, long lastMessageId); /// <summary> /// Implementation of this method should queue a message for the specific client /// </summary> /// <param name="clientPublicToken"></param> /// <param name="name"></param> /// <param name="contents"></param> void SendMessage(string clientPublicToken, string name, object contents); /// <summary> /// Implementation of this method should queue a message for all the clients /// </summary> /// <param name="name"></param> /// <param name="contents"></param> void SendMessage(string name, object contents); /// <summary> /// Implementation of this method should return a specific comet client /// </summary> /// <param name="clientPrivateToken"></param> /// <returns></returns> CometClient GetCometClient(string clientPrivateToken); /// <summary> /// Implementation of this method should remove a client from the cache /// </summary> /// <param name="clientPrivateToken"></param> void KillIdleCometClient(string clientPrivateToken); } }
InProcCometStateProvider类：
InProcCometStateProvider类实现了ICometStateProvider接口，并且提供了一个很好的范例，针对这个类，我们可以想象很多很好的拓展，诸如调用AO组件，封装报警信息等等。
InProcCometStateProvider类包含类一个私有的内部类InProcCometStateProvider，实际上可以理解为一种对消息的简单封装，设计的时候考虑到需要关联CometClient和Message，其实也可以单独作为一个外部类来设计。不过Adapter本身不应该太多关联类，这样做也是权衡了一些拓展上的需求。
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace MethodWorx.AspNetComet.Core { /// <summary> /// Class InProcCometStateProvider /// /// This class provides an implementation of ICometStateProvider that keeps the /// information in memory. This provider is not scalable as it will not run on a server /// farm but demonstrates how you should implemement the provider. /// </summary> public class InProcCometStateProvider : ICometStateProvider { /// <summary> /// Private class which holds the state of each connected client /// </summary> private class InProcCometClient { public CometClient CometClient; public Dictionary<long, CometMessage> Messages = new Dictionary<long, CometMessage>(); public long NextMessageId = 1; } /// <summary> /// Cache of clients /// </summary> private Dictionary<string, InProcCometClient> publicClients = new Dictionary<string, InProcCometClient>(); private Dictionary<string, InProcCometClient> privateClients = new Dictionary<string, InProcCometClient>(); private static object state = new object(); #region ICometStateProvider Members /// <summary> /// Store the new client in memory /// </summary> /// <param name="cometClient"></param> public void InitializeClient(CometClient cometClient) { if (cometClient == null) throw new ArgumentNullException("cometClient"); lock (state) { // ok, ensure we dont already exist if (publicClients.ContainsKey(cometClient.PublicToken) || privateClients.ContainsKey(cometClient.PrivateToken)) throw CometException.CometClientAlreadyExistsException(); InProcCometClient inProcCometClient = new InProcCometClient() { CometClient = cometClient }; // stick the client int he arrays // ready to be used publicClients.Add(cometClient.PublicToken, inProcCometClient); privateClients.Add(cometClient.PrivateToken, inProcCometClient); } // ok, they are in there ready to be used } /// <summary> /// Get the messages for a specific client /// </summary> /// <param name="clientPrivateToken"></param> /// <param name="lastMessageId"></param> /// <returns></returns> public CometMessage[] GetMessages(string clientPrivateToken, long lastMessageId) { if(string.IsNullOrEmpty(clientPrivateToken)) throw new ArgumentNullException("clientPrivateToken"); lock (state) { if (!privateClients.ContainsKey(clientPrivateToken)) throw CometException.CometClientDoesNotExistException(); // // ok, get the client InProcCometClient cometClient = privateClients[clientPrivateToken]; List<long> toDelete = new List<long>(); List<long> toReturn = new List<long>(); // wicked, we have the client, so we can get its messages from our list // we delete any before the last messageId becuase we dont want them foreach(long key in cometClient.Messages.Keys) { if(key <= lastMessageId) toDelete.Add(key); else toReturn.Add(key); } // delete the ones from the messages foreach (long key in toDelete) { cometClient.Messages.Remove(key); } // and return the ones in the toReturn array List<CometMessage> cometMessages = new List<CometMessage>(); foreach (long key in toReturn) { cometMessages.Add(cometClient.Messages[key]); } return cometMessages.ToArray(); } } /// <summary> /// Send a message to a specific client /// </summary> /// <param name="clientPublicToken"></param> /// <param name="name"></param> /// <param name="contents"></param> public void SendMessage(string clientPublicToken, string name, object contents) { if (string.IsNullOrEmpty(clientPublicToken)) throw new ArgumentNullException("clientPublicToken"); if (contents == null) throw new ArgumentNullException("contents"); lock (state) { if (!publicClients.ContainsKey(clientPublicToken)) throw CometException.CometClientDoesNotExistException(); // // ok, get the client InProcCometClient cometClient = publicClients[clientPublicToken]; // ok, stick the message in the array CometMessage message = new CometMessage(); message.Contents = contents; message.Name = name; message.MessageId = cometClient.NextMessageId; // increment cometClient.NextMessageId++; cometClient.Messages.Add(message.MessageId, message); } } /// <summary> /// Send a message to all the clients /// </summary> /// <param name="name"></param> /// <param name="contents"></param> public void SendMessage(string name, object contents) { if (contents == null) throw new ArgumentNullException("contents"); lock (state) { foreach (InProcCometClient cometClient in publicClients.Values) { // ok, stick the message in the array CometMessage message = new CometMessage(); message.Contents = contents; message.Name = name; message.MessageId = cometClient.NextMessageId; // increment cometClient.NextMessageId++; cometClient.Messages.Add(message.MessageId, message); } } } /// <summary> /// Get the client from the state provider /// </summary> /// <param name="clientPrivateToken"></param> /// <returns></returns> public CometClient GetCometClient(string clientPrivateToken) { if (!this.privateClients.ContainsKey(clientPrivateToken)) throw CometException.CometClientDoesNotExistException(); // return the client private token return this.privateClients[clientPrivateToken].CometClient; } /// <summary> /// Remove an idle client from the memory /// </summary> /// <param name="clientPrivateToken"></param> public void KillIdleCometClient(string clientPrivateToken) { if (!this.privateClients.ContainsKey(clientPrivateToken)) throw CometException.CometClientDoesNotExistException(); // get the client InProcCometClient ipCometClient = this.privateClients[clientPrivateToken]; // and remove the dictionarys this.privateClients.Remove(ipCometClient.CometClient.PrivateToken); this.publicClients.Remove(ipCometClient.CometClient.PublicToken); } #endregion } }
PS:可以说这篇随笔中将COMET IM的几个最容易拓展的类进行了介绍，核心部分将在下一篇随笔中进行讲解，欢迎大家讨论并拍砖。同时预祝大家春节愉快！
