引用自：http://blog.csdn.net/wanglipo/article/details/7256886
1.客户端请求
<script type="text/javascript">
var HttpRequest;
function CreateXmlHttpRequest()
{
if(window.XMLHttpRequest)
{
HttpRequest=new XMLHttpRequest();
}
else if(window.ActiveXObject)
{
HttpRequest=new ActiveXObject("MICROST.XMLHTTP");
}
}
function Send()
{
document.getElementById("test").innerHTML="等待返回信息
";
CreateXmlHttpRequest();
if(HttpRequest!=null)
{
HttpRequest.onreadystatechange=ShowMessage;
HttpRequest.open("GET","Handler.ashx?name="+escape("leon")+"&m"+Math.random());
HttpRequest.send();
}
}
function ShowMessage()
{
if(HttpRequest.readyState==4&&HttpRequest.status==200)
{
if(HttpRequest.responseText.length>0)
{
alert(HttpRequest.responseText);//收到信息
//如果有信息返回 重新发送请求 递归
Send();
}
}
}
</script>
var HttpRequest;
function CreateXmlHttpRequest()
{
if(window.XMLHttpRequest)
{
HttpRequest=new XMLHttpRequest();
}
else if(window.ActiveXObject)
{
HttpRequest=new ActiveXObject("MICROST.XMLHTTP");
}
}
function Send()
{
document.getElementById("test").innerHTML="等待返回信息
";CreateXmlHttpRequest();
if(HttpRequest!=null)
{
HttpRequest.onreadystatechange=ShowMessage;
HttpRequest.open("GET","Handler.ashx?name="+escape("leon")+"&m"+Math.random());
HttpRequest.send();
}
}
function ShowMessage()
{
if(HttpRequest.readyState==4&&HttpRequest.status==200)
{
if(HttpRequest.responseText.length>0)
{
alert(HttpRequest.responseText);//收到信息
//如果有信息返回 重新发送请求 递归
Send();
}
}
}
</script>
2.服务的如何hold请求
Code<!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/
-->public class Handler : IHttpHandler
{
private bool ok = true;
public void ProcessRequest(HttpContext context)
{
ok = true;
while (ok)//超时设置ok为false即可
{
//循环检查是否有信息存在
Check();
//防止循环太频繁
System.Threading.Thread.Sleep(1000);
}
}
private void Check()
{
List<message> list = new List<message>();//信息列表
string str = "";
lock (im.mlist)
{
if (im.mlist.Count > 0)
{
foreach (message m in im.mlist)
{
if (m.username == HttpContext.Current.Request["name"].ToString())
{
list.Add(m);
str = m.messagecontent;
break;
}
}
if (list.Count > 0)
{
foreach (message m in list)
{
im.mlist.Remove(m);
}
}
//收到信息 循环结束
ok = false;
if (list.Count > 0)
{
//推信息
HttpContext.Current.Response.Write("收到信息：" + str);
}
}
}
}
public bool IsReusable
{
get
{
return false;
}
}
}