页面间隔半秒钟更新时间 Asp.net使用Comet开发http长连接示例分享

好处:1.和AJAX轮询比起来 节省资源,并且延迟小, 2.和webSocket比起来,适用的场景比较广泛。

1.先建立一个Asp.net MVC的空项目

添加一个控制器  (同样的代码在Asp.net WebForm中也是可以使用的)

2.再兴建一个控制器和View 用于显示HTML

        public ActionResult Index()
        {
            return View();
        }

    }
</div>

View的代码比较重要

        $(document).ready(function () {
            getData();
        });

        function getData() {
            loadXMLDoc("/Comet/Test");
        }

        //新建一个XHR
function createRequest() {
            if (window.XMLHttpRequest && !(window.ActiveXObject)) {
                try {
                    req = new XMLHttpRequest();
                } catch (e) {
                    req = false;
                }        // branch for IE/Windows ActiveX version  
            } else if (window.ActiveXObject) {
                try { req = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {
                    try {
                        req = new ActiveXObject("Microsoft.XMLHTTP");
                    } catch (e) {
                        req = false;
                    }
                }
            }
        }

        //发起请求
function loadXMLDoc(url) {
            try {
                if (req) {
                    req.abort();
                    req = false;
                }
                createRequest();
                if (req) {
                    req.onreadystatechange = processReqChange;
                    req.open("GET", url, true);
                    req.send("");
                } else {
                    alert('unable to create request');
                }
            } catch (e) { alert(e.message); }
        }

        //检查状态
function processReqChange() {
            if (req.readyState == 3) {
                try {
                    ProcessInput(req.responseText);
                    if (req.responseText.length > 3000) {
               &nb