用IHttpAsyncHandler实现Comet

实现功能：登录、获取用户列表、退出；JS库采用jQuery1.32
解决方案

运行时的效果图：
输入帐号后，点击“Login”按钮后显示当前在线的用户列表，点击“Logout”按钮后当前用户退出后向其它在线用户推送新的在线用户列表；
 
Default.aspx页面引用的两个js脚本，jQuery1.3.2,WebIM.js;

< script  src ="Scripts/jquery-1.3.2.min.js"  type ="text/javascript" ></ script >
< script  src ="Scripts/WebIM.js"  type ="text/javascript" ></ script >

HTML DOM代码如下：

     < asp:Label  ID ="Label1"  runat ="server"  Text ="帐号" ></ asp:Label >
     < input  id ="txtLoginID"  type =""   />< input  id ="btnLogin"  type ="button"  value ="Login"   />< input
         id ="btnLogout"  type ="button"  value ="Logout"   />
     < br  />
     < div  id ="divUserList" >
     </ div >
     < br  />
    广播内容:
     < input  type ="text"  id ="content"   />< br  />
    消息记录：
     < div  id ="divResult" >
     </ div >
     < input  type ="button"  id ="btnSend"  value ="广播"   />

WebIM.js脚本

// / <reference path="jquery-1.3.2.min.js" >
$(document).ready( function () {
     // 状态，代表是否登录
     var  _logined  =   false ;

     // 登录，登录成功后，获取在线用户列表，
     function  login() {
        $.post( " comet_broadcast.asyn " , { action:  ' login ' , uid: $( " #txtLoginID " ).val() },
         function (data, status) {
             if  (data  ==   " OK " ) {
                _logined  =   true ;
                getuserlist();
            }
        });
    }

     // 获取在线用户列表，获取列表后，进入消息等待
     function  getuserlist() {
        $.post( " comet_broadcast.asyn " , { action:  ' getuserlist ' , uid: $( " #txtLoginID " ).val() },
         function (data, status) {
             // alert('getuserlist' + data);
             var  result  =  $( " #divResult " );
            result.html(result.html()  +   " <br/> "   + " 用户列表： "   + data);
            wait();
        });
    }

     // 退出
     function  logout() {
        $.post( " comet_broadcast.asyn " , { action:  ' logout ' , uid: $( " #txtLoginID " ).val() },
         function (data, status) { _logined  =   false ; alert(data); }
         );
    }

     // 消息等待，接收到消息后显示，发起下一次的消息等待
     function  wait() {
        $.post( " comet_broadcast.asyn " , { action:  ' connect ' , uid: $( " #txtLoginID " ).val() },
            function (data, status) {
               //  alert('wait' + data);
                var  result  =  $( " #divResult " );
               result.html(result.html()  +   " <br/> "   + " 用户列表: " +  data);

                // 服务器返回消息,再次立连接
                if  (_logined) {
                   wait();
               }

           },  " html "
           );
    }
     // 附加事件
     $( " #btnLogin " ).click( function () {  if  ($( " #txtLoginID " ).val()  ==   '' ) alert( ' 空 ' ); login(); });
    $( " #btnLogout " ).click( function () { logout(); });

});

服务端代码：

public   class  WebIMAsyncHandler : IHttpAsyncHandler

    {
         #region  IHttpAsyncHandler 成员

         public  IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb,  object  extraData)
        {
             string  _UID  =  context.Request.Params[ " uid " ];

            WebIMClientAsyncResult _AsyncResult  =   new  WebIMClientAsyncResult(context, cb, extraData);

             string  _Content  =  context.Request.Params[ " content " ];
             string  _Action  =  context.Request.Params[ " action " ];
             if  (_Action  ==   " login " )
            {
                _UID  =  context.Request.Params[ " uid " ];
                _AsyncResult.LoginID  =  _UID;
                WebIMMessageHandler.Instance().Login(_UID, _AsyncResult);
            }
             else   if  (_Action  ==   " logout " )
            {
                _AsyncResult.LoginID  =  _UID;
                WebIMMessageHandler.Instance().Logout(_UID, _AsyncResult);
            }
             else   if  (_Action  ==   " connect " )
            {
                _AsyncResult.LoginID  =  _UID;
                WebIMMessageHandler.Instance().Connect(_AsyncResult);
            }
             else   if  (_Action  ==   " getuserlist " )
            {
                _AsyncResult.LoginID  =  _UID;
                WebIMMessageHandler.Instance().GetUserList(_AsyncResult);
            }


             // 调用
            WebIMMessageHandler.Instance().AddMessage(_Content, _AsyncResult);
             return  _AsyncResult;
        }

         public   void  EndProcessRequest(IAsyncResult result)
        {

        }

         #endregion

         #region  IHttpHandler 成员

         public   bool  IsReusable
        {
             get  {  return   false ; ; }
        }

         public   void  ProcessRequest(HttpContext context)
        {
             throw   new  NotImplementedException();
        }

         #endregion
    }

     public   class  WebIMClientAsyncResult : IAsyncResult
    {

         bool  m_IsCompleted  =   false ;
         private  HttpContext m_Context;
         private  AsyncCallback m_Callback;
         private   object  m_ExtraData;
         private   string  m_Content;
         private   string  m_LoginID  =   string .Empty;


         public  WebIMClientAsyncResult(HttpContext p_Context, AsyncCallback p_Callback,  object  p_ExtraData)
        {
             this .m_Context  =  p_Context;
             this .m_Callback  =  p_Callback;
             this .m_ExtraData  =  p_ExtraData;
        }
         ///   <summary>
         ///  用户编号
         ///   </summary>
         public   string  LoginID
        {
             get
            {
                 return  m_LoginID;
            }
             set
            {
                m_LoginID  =  value;
            }
        }
         ///   <summary>
         ///  发送消息的内容，暂时未使用到
         ///   </summary>
         public   string  Content
        {
             get
            {
                 return  m_Content;
            }
             set
            {
                m_Content  =  value;
            }
        }
         #region  IAsyncResult 成员

         public   object  AsyncState
        {
             get  {  return   null ; }
        }

         public  WaitHandle AsyncWaitHandle
        {
             get  {  return   null ; }
        }

         public   bool  CompletedSynchronously
        {
             get  {  return   false ; }
        }

         public   bool  IsCompleted
        {
             get  {  return  m_IsCompleted; }
        }

         #endregion

         ///   <summary>
         ///  向客户端响应消息
         ///   </summary>
         ///   <param name="data"></param>
         public   void  Send( object  data)
        {
             try
            {
                m_Context.Response.Write( this .Content);
                 if  (m_Callback  !=   null )
                {
                    m_Callback( this );
                }
                
            }
             catch  { }
             finally  
            {
                m_IsCompleted  =   true ; 
            }
        }
    }

     public   class  WebIMMessageHandler
    {
         private   static   readonly  WebIMMessageHandler m_Instance  =   new  WebIMMessageHandler();
         // 记录所有请求的客户端
         List < WebIMClientAsyncResult >  m_Clients  =   new  List < WebIMClientAsyncResult > ();
         string  m_Users  =   string .Empty;
         public  WebIMMessageHandler()
        {

        }

         public   static  WebIMMessageHandler Instance()
        {
             return  m_Instance;
        }

         ///   <summary>
         ///  登录
         ///   </summary>
         ///   <param name="p_LoginID"></param>
         ///   <param name="p_ClientAsyncResult"></param>
         public   void  Login( string  p_LoginID, WebIMClientAsyncResult p_ClientAsyncResult)
        {
             bool  _Logined  =   false ;
             foreach  (WebIMClientAsyncResult _Item  in  m_Clients)
            {
                 if  (_Item.LoginID  ==  p_LoginID)
                {
                    p_ClientAsyncResult.Content  =   " 你已登录 " ;
                    _Logined  =   true ;
                     break ;
                }
            }
             if  ( ! _Logined)
            {
                 // m_Clients.Add(p_ClientAsyncResult);
                p_ClientAsyncResult.Content  =   " OK " ;
            }
            p_ClientAsyncResult.Send( null );


        }

         private   string  GetUsers()
        {
             string  _Users  =   string .Empty;
             foreach  (WebIMClientAsyncResult _Item  in  m_Clients)
            {
                _Users  +=  _Item.LoginID  +   " , " ;
            }
             return  _Users;
        }

         public   void  Logout( string  p_LoginID, WebIMClientAsyncResult p_ClientAsyncResult)
        {
             foreach  (WebIMClientAsyncResult _Item  in  m_Clients)
            {
                 if  (_Item.LoginID  ==  p_LoginID)
                {
                    m_Clients.Remove(_Item);
                     break ;
                }
            }
            p_ClientAsyncResult.Content  =   " 退出成功 " ;
            p_ClientAsyncResult.Send( null );
             // UpdateUserList();

             string  _Users  =  GetUsers();
             foreach  (WebIMClientAsyncResult _Item  in  m_Clients)
            {
                _Item.Content  =  _Users;
                _Item.Send( null );
            }
            m_Clients.Clear();
        }

         public   void  GetUserList(WebIMClientAsyncResult p_ClientAsyncResult)
        {
            Connect(p_ClientAsyncResult);
             string  _Users  =  GetUsers();
             foreach  (WebIMClientAsyncResult _Item  in  m_Clients)
            {
                _Item.Content  =  _Users;
                _Item.Send( null );
            }
            m_Clients.Clear();
        }

         public   void  Connect(WebIMClientAsyncResult p_Client)
        {
             bool  _Exists  =   false ;
             foreach  (WebIMClientAsyncResult _Item  in  m_Clients)
            {
                 if  (_Item.LoginID  ==  p_Client.LoginID)
                {
                    _Exists  =   true ;
                     break ;
                }
            }
             if  ( ! _Exists)
            {
                m_Clients.Add(p_Client);
            }
        }

         public   void  UpdateUserList()
        {
             string  _Users  =  GetUsers();
             foreach  (WebIMClientAsyncResult result  in  m_Clients)
            {
                result.Content  =  m_Users;
                result.Send( null );
            }
            m_Clients.Clear();

        }

         ///   <summary>
         ///  广播消息
         ///   </summary>
         ///   <param name="p_Message"></param>
         ///   <param name="p_AsyncResult"></param>
         public   void  AddMessage( string  p_Message, WebIMClientAsyncResult p_ClientAsyncResult)
        {
             /// /保持联连
             // if (p_Message == "-1")
             // {
             //     m_Clients.Add(p_ClientAsyncResult);

             // }
             // else
             // {
             //      // 将当前请求的内容输出到客户端
             //     p_ClientAsyncResult.Content = p_Message;
             //     p_ClientAsyncResult.Send(null);

             //      // 否则将遍历所有已缓存的client,并将当前内容输出到客户端
             //     foreach (WebIMClientAsyncResult result in m_Clients)
             //     {
             //         result.Content = p_Message;
             //         result.Send(null);
             //     }

             //      // 清空所有缓存
             //     m_Clients.Clear();
             // }
        }

    }

添加配置文件信息:

         < httpHandlers >
             < add  path ="comet_broadcast.asyn"  type ="CometSample.WebIMAsyncHandler"  verb ="POST,GET" />
         </ httpHandlers >

源码下载： CometSample.rar 下节将实现信息的发送与接收；