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weiconfig:
1 <system.web> 2 <httpHandlers> 3 <add path="comet_broadcast.ashx" type="AsnyHandler" verb="POST,GET"/> 4 </httpHandlers> 5 <compilation debug="true" targetFramework="4.0"/> 6 <httpRuntime/> 7 </system.web>
一般处理程序Handler1：
1 public class Handler1 : IHttpHandler 2 { 3 4 public void ProcessRequest(HttpContext context) 5 { 6 context.Response.ContentType = "text/plain"; 7 context.Response.Write("Hello World:" + DateTime.Now.ToString("HH:mm:ss"));//需要输出特定的信息的,可以在这里处理,例如读取数据库的最新参数啊,获取memcached的值之类的都行. 8 } 9 10 public bool IsReusable 11 { 12 get 13 { 14 return false; 15 } 16 } 17 }
页面：
1 <html xmlns="http://www.w3.org/1999/xhtml"> 2 <head runat="server"> 3 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 4 <title></title> 5 <style type="text/css"> 6 * { 7 font-size: 12px; 8 } 9 10 #divResult { 11 border: 1px solid #000; 12 width: 250px; 13 } 14 </style> 15 <script src="Scripts/jquery-1.3.2.min.js"></script> 16 <script type="text/javascript"> 17 function fUpdateData(data) { 18 19 $.post("comet_broadcast.ashx", { content: data }, 20 function (data, status) { 21 alert(data); 22 var result = $("#divResult"); 23 result.html(result.html() + "<br/>" + data); 24 // $("#divResult").html(data); 25 //服务器返回消息,再次请求后台数据 26 fGetData(); 27 }, "html" 28 ); 29 } 30 //获取服务器最新信息 31 function fGetData() { 32 $.ajax({ 33 type: ‘GET‘, 34 url: ‘Handler1.ashx‘, 35 success: function (data) { 36 37 fUpdateData(data); 38 } 39 }); 40 } 41 $(document).ready(function () { 42 //初始化 43 fGetData(); 44 }); 45 </script> 46 </head> 47 <body> 48 <form id="form1" runat="server"> 49 <div> 50 后台推送最新消息： 51 <div id="divResult"> 52 </div> 53 </div> 54 </form> 55 </body> 56 </html>
AsnyHandler类与 myAsynResult类：
1 public class AsnyHandler:IHttpAsyncHandler 2 { 3 public AsnyHandler() 4 { 5 } 6 7 public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) 8 { 9 //myAsynResult为实现了IAsyncResult接口的类，当不调用cb的回调函数时，该请求不会返回到给客户端，会一直处于连接状态 10 myAsynResult asyncResult = new myAsynResult(context, cb, extraData); 11 String content = context.Request.Params["content"]; 12 13 //向Message类中添加该消息 14 Messages.Instance().AddMessage(content, asyncResult); 15 return asyncResult; 16 } 17 18 #region 不必理会 19 20 public void EndProcessRequest(IAsyncResult result) 21 { 22 23 } 24 25 public bool IsReusable 26 { 27 get { return false; ; } 28 } 29 30 public void ProcessRequest(HttpContext context) 31 { 32 } 33 #endregion 34 } 35 public class myAsynResult : IAsyncResult 36 { 37 bool _IsCompleted = false; 38 private HttpContext context; 39 private AsyncCallback cb; 40 private object extraData; 41 public myAsynResult(HttpContext context, AsyncCallback cb, object extraData) 42 { 43 this.context = context; 44 this.cb = cb; 45 this.extraData = extraData; 46 } 47 private string _content; 48 public string Content { 49 get {return _content;} 50 set{_content=value;} 51 } 52 53 #region IAsyncResult接口 54 public object AsyncState 55 { 56 get { return null; } 57 } 58 59 public System.Threading.WaitHandle AsyncWaitHandle 60 { 61 get { return null; } 62 } 63 64 public bool CompletedSynchronously 65 { 66 get { return false; } 67 } 68 public bool IsCompleted 69 { 70 get { return _IsCompleted; } 71 } 72 #endregion 73 74 //在Message类中的添加消息方法中，调用该方法，将消息输入到客户端，从而实现广播的功能 75 public void Send(object data) 76 { 77 context.Response.Write(this.Content); 78 if (cb!=null) 79 { 80 cb(this); 81 } 82 _IsCompleted = true; ; 83 } 84 }
Messages类：
1 public class Messages 2 { 3 //记录所有请求的客户端 4 List<myAsynResult> clients = new List<myAsynResult>(); 5 6 #region 实现该类的单例 7 private static readonly Messages _Instance = new Messages(); 8 private Messages() 9 { 10 } 11 public static Messages Instance() 12 { 13 return _Instance; 14 } 15 #endregion 16 17 public void AddMessage(string content,myAsynResult asyncResult) 18 { 19 //当传入的内容为"-1"时，表示为建立连接请求，即为了维持一个从客户端到服务器的连接而建立的连接 20 //此时将该连接保存到 List<myAsynResult> clients中，待再有消息发送过来时，该连接将会被遍历，并且会将该连接输出内容后，结束该连接 21 if (content=="-1") 22 { 23 clients.Add(asyncResult); 24 } 25 else 26 { 27 //将当前请求的内容输出到客户端 28 asyncResult.Content = content; 29 asyncResult.Send(null); 30 31 //否则将遍历所有已缓存的client,并将当前内容输出到客户端 32 foreach (myAsynResult result in clients) 33 { 34 result.Content = content; 35 result.Send(null); 36 } 37 38 //清空所有缓存 39 clients.Clear(); 40 } 41 } 42 }
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原文地址：http://www.cnblogs.com/jbps/p/4838559.html
