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