项目：B/S 服务器推送技术

Comet

PustLet

WebSocket

 

Ajax长连接

function connection(){

        $.ajax({

            type:"GET",

            url:"/api2/session/event?",

            data:{

                "uid":obj.uid,

                "sessionID":"cool"

            },

            success:function(serverData){

                   connection();

            },

            error:function(XMLHttpRequest, textStatus, errorThrown){

                   connection();

            }

        });

    }

(一)当用户登陆时,发送等待请求给服务器wait()

function wait() {

        $.post("comet_broadcast.asyn", { content: "-1" },

         function (data, status) {

             var result = $("#divResult");

             result.html(result.html() + "<br/>" + data);

             

             //服务器返回消息,再次立连接

             wait();

         }, "html"

         );

    }

   向服务器发送信息send()

function send() {

     // 向comet_broadcast.asyn发送请求

    // 消息体为文本框content中的内容

    // 请求接收类为AsnyHandler

    $.post("comet_broadcast.asyn", { 

        content: $("#content").val() 

    });



    //清空内容

    $("#content").val("");

    }

    //初始化连接

wait();

(二)AsnyHandler异步处理

using System;

using System.Collections.Generic;

using System.Web;

using System.Threading;



/// <summary>

/// Summary description for AsnyHandler

/// </summary>

public class AsnyHandler:IHttpAsyncHandler

{

    public AsnyHandler()

    {

    }



    public IAsyncResult BeginProcessRequest(HttpContext context, 

AsyncCallback cb, object extraData)

    {

        //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

        myAsynResult asyncResult = new myAsynResult(context, cb, 

extraData);

        String content = context.Request.Params["content"];



        //向Message类中添加该消息

        Messages.Instance().AddMessage(content, asyncResult);

        return asyncResult;

    }



    #region 

    

    public void EndProcessRequest(IAsyncResult result)

    {

      

    }



    public bool IsReusable

    {

        get { return false; ; }

    }



    public void ProcessRequest(HttpContext context)

    {

    }



    #endregion

}



public class myAsynResult : IAsyncResult

{

    bool _IsCompleted = false;

    private HttpContext context;

    private AsyncCallback cb;

    private object extraData;



    public myAsynResult(HttpContext context, AsyncCallback cb, object 

extraData)

    {

        this.context = context;

        this.cb = cb;

        this.extraData = extraData;

    }



    private string _content;



    public string Content { 

        get {

        return _content;

    }

        set {

        _content=value;

    } 

    }



    #region IAsyncResult接口



    public object AsyncState

    {

        get { return null; }

    }



    public System.Threading.WaitHandle AsyncWaitHandle

    {

        get { return null; }

    }



    public bool CompletedSynchronously

    {

        get { return false; }

    }

    public bool IsCompleted

    {

        get { return _IsCompleted; }

    }



    #endregion



    //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

    public void Send(object data)

    {

            context.Response.Write(this.Content);

            if (cb!=null)

            {

                cb(this);

            }

            _IsCompleted = true; ;

    }

}

(三)Message

using System;

using System.Collections.Generic;

using System.Web;



/// <summary>

/// Summary description for Messages

/// </summary>

public class Messages

{

    //记录所有请求的客户端

    List<myAsynResult> clients = new List<myAsynResult>();



    #region 实现该类的单例

    private static readonly Messages _Instance = new Messages();

    private Messages()

    {

    }

    public static Messages Instance()

    {

        return _Instance;

    }

    #endregion



    public void AddMessage(string content,myAsynResult asyncResult)

    {

        //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

        //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

        if (content=="-1")

        {

            clients.Add(asyncResult);

        }

        else

        {

            //将当前请求的内容输出到客户端

            asyncResult.Content = content;

            asyncResult.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 (myAsynResult result in clients)

            {

                result.Content = content;

                result.Send(null);

            }



            //清空所有缓存

            clients.Clear();

        }

    }

}

 

(四)Web.Config

<?xml version="1.0"?>

<configuration>

    <system.web>

        <httpHandlers>

            <add path="comet_broadcast.asyn" type="AsnyHandler" verb="POST,GET"/>

        </httpHandlers>

        <compilation debug="true"/></system.web>

</configuration>

出现的问题:

1.加入到IIS为什么就无法运行?

2.添加了async的处理程序还是无法运行?

3.HTTP长连接是Comet还是PushLet还是WebSocket?或者是轮询还是iframe流?

内容参考:http://www.cnblogs.com/hanxianlong/archive/2010/04/27/1722018.html