comet (Reverse AJAX) is primarily connected through an HTTP long connection, maintaining a connection to the server, implementing server PUSH and two-way communication, and following the example to learn how to use it
Benefits: 1. Save resources compared to Ajax polling, and latency is small, 2. Compared with websocket, the applicable scenarios are quite extensive. 1. First create an empty project for asp.net MVC Add a controller (the same code can be used in asp.net webform) code is as follows: public class Cometc Ontroller:controller { public ActionResult Test () { Response.Buffer = false; while (true) ) { Response.Write (datet Ime. Now.tostring ("Yyyy-mm-dd HH:mm:ss FFF") + "|"); Thread.Sleep (500); //not running here return Content (""); } } { 2. Build a controller and view to display the html code as follows: public class Hom Econtroller:controller { &NBSp // //Get:/home/ public ActionResult Index () { return View () &NBS } P } View Code is more important code is as follows: @{ Layout = null; <! DOCTYPE html> <html> <head> <title>Index</title> <script type= "Text/javascript" src= "Http://code.jquery.com/jquery-1.7.1.min.js" ></script> <script language= "JavaScript" > var req = false; var lastdelimiterposition =-1; $ (document). Ready (function () { GetData () &n Bsp }); function GetData () { Loadxmldoc ("/comet/test") ); &nbSp } //Create a XHR function Createrequest () { if (window. XMLHttpRequest &&! (Window. ActiveXObject)) { try { req = new XMLHttpRequest (); } catch (e) { &NB Sp req = false; //branch for ie/windows ActiveX vers Ion /else if window. ActiveXObject] { try {req = new ActiveXObject ("Msxml2.xmlhttp"); catch (e) { try { &NBS P   req = new ActiveXObject ("Microsoft.XMLHTTP"); } catch (e) { &NB Sp req = false; & nbsp { / } //Initiating request Func tion Loadxmldoc (URL) { try { &N Bsp if (req) { Req.abort () req = false; Createre Quest (); if (req) {   Req.onreadystatechange = Processreqchange; Req.open ("Get", url, True); req.send (""); } else { & nbsp Alert (' Unable to create request '); } catch (e) {alert (E. message); } /Check Status function Processreqchange () { &nbs P if (req.readystate = 3) { try { &NBSP ; ProcessInput (Req.responsetext); if (Req.responseText.length > 3000) { L Astdelimiterposition =-1; GetData (); & nbsp } catch (e) { &NB Sp alert (e.message); } //split string function ProcessInput (input) { &NB Sp var text = input; var nextdelimiter = text.indexof (' | ', Lastdelimiterposition + 1); if (Nextdelimiter!=-1) { &NBS P var timeStamp = text.substring (nextdelimiter + 1); if (Timestamp.length > 0) { lastdelimiterposition = Nextdelimiter; processtime (TimeStamp); } } //output or trigger what event function Processtime (time) { document.getElementById (' Div1 '). InnerHTML = time; } </script> </head> <body> <div> &N Bsp <div id= "Div1" > </div> <div id= "Div2" > </div> </div> </body> </html> 3. The final effect is: on the page to display a time, every half a second update aTimes Of course, when you get the content, you do what you want to do ... Update Dom or execute JS, (OK with Eval this method ~ ~) 4. This example is just an implementation based on asynchronous JavaScript, is actually available through <iframe> and <script> These two tags are implemented, especially the script tags can access and execute Cross-domain javascriptStart building with 50+ products and up to 12 months usage for Elastic Compute Service
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