开发分布式WebIm--3（Comet模型）

最新推荐文章于 2020-11-24 16:57:51 发布

转载最新推荐文章于 2020-11-24 16:57:51 发布 · 155 阅读

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原文链接：http://www.cnblogs.com/nevermad/archive/2010/04/21/1717013.html

文章标签：

#ui #json

本文介绍如何使用ASP.NET实现Comet技术，通过IHttpAsyncHandler接口处理异步请求，实现长轮询效果，以达到服务器推送数据给客户端的目的。文中详细展示了如何创建CometAsyncHandler类，以及如何配置web.config。

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原文是：http://www.codeproject.com/KB/aspnet/CometAsync.aspx

Asp.net环境下实现Comet就要用到 IHttpAsyncHandler接口

并实现其中的BeginProcessRequest和EndProcessRequest方法

BeginProcessRequest方法中的HttpContext包含了Response和Request对象，AsyncCallback用于异步调用结束，运行结束后需要返回一个IAsyncResult对象。

我在BeginProcessRequest函数中通过Request获取了一个名为ElementData的JSon字符串，并通过Element解析出用户名和在线状态。

CometAsyncResult构造函数只是简单的保存了HttpContext、AsyncCallback这两个对象，AddCometAsyncResult函数则实现了根据用户名获取全网中的留言信息、复制好友列表到聊天服务器、好友状态交换等业务逻辑。当然还有一点最为关键的，就是把用户名和HttpContext、AsyncCallback这两个对象对应起来，这样才能通过用户名来发送消息。当你完成这一切的时候，Comet模型就建立起来了，非常的简单。根据我测试windows2003+IIS6.0环境下可以同时4000-8000个链接，windows2008+IIS7.0环境下可达到15000个链接。

代码

using System;
using System.Data;
using System.Configuration;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Threading;
using System.Web;
using PCBaseLib.Entity;
using CometAsync.Remoting;

namespace CometAsync.Comet
{
     public class CometAsyncHandler : IHttpAsyncHandler
    {
         #region IHttpAsyncHandler Members

         public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {


                 // 保存状态

            CometAsyncResult result = new CometAsyncResult(context.Response, cb, extraData);
            Element Ele = null ;
             if (context.Request.Form[ " ElementData " ] != null )

                Ele = new Element(context.Request.Form[ " ElementData " ], true );
             else
            {
                Ele = new Element( " test " );
                Ele[ " From " ] = " user " + HttpContextRemoting.UsersOnline.Count.ToString();
                Ele[ " State " ] = " 0 " ;
            }
            result.AddCometAsyncResult(Ele[ " From " ], Ele[ " State " ]);

                 //   ok, return it
                 return result;

        }

         public void EndProcessRequest(IAsyncResult result)
        {

        }

         #endregion

         #region IHttpHandler Members

         public bool IsReusable
        {
             get { return false ; }
        }

         public void ProcessRequest(HttpContext context)
        {
             throw new InvalidOperationException( " ASP.NET Should never use this property " );
        }

         #endregion
    }
}

运行上述代码，请在web.config文件中加入httpHandlers节，注册访问页由你的类来处理，如下CometLink.ashx的处理函数、命名空间全名为：CometAsync.Comet.CometAsyncHandler

代码

    < httpHandlers >

       < add verb ="GET, POST" path ="CometLink.ashx" type ="CometAsync.Comet.CometAsyncHandler, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="SendMessage.ashx" type ="CometAsync.IM_Command.SendMessage, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="Join.ashx" type ="CometAsync.IM_Command.Join, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="Agree.ashx" type ="CometAsync.IM_Command.Agree, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="Login.ashx" type ="CometAsync.IM_Command.Login, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="Refuse.ashx" type ="CometAsync.IM_Command.Refuse, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="Presence.ashx" type ="CometAsync.IM_Command.Presence, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="PresenceEx.ashx" type ="CometAsync.IM_Command.PresenceEx, CometAsync" validate ="false" />
       < add verb ="GET, POST" path ="InfoSet.ashx" type ="CometAsync.IM_Command.InfoSet, CometAsync" validate ="false" />
     </ httpHandlers >

转载于:https://www.cnblogs.com/nevermad/archive/2010/04/21/1717013.html