How to send data from a server to a client without a native HTTP request made by client.
This can be implemented in Chatting Applications, Automatic updates of some data.
So what is this ?
Comet is a programming technique that enables web servers to send data to the client without having any need for the client to request it. It allows creation of event-driven web applications which are hosted in the browser.
Try reading from this . http://en.wikipedia.org/wiki/Comet_%28programming%29
From where do i got to know of this is http://stackoverflow.com/questions/3226688/web-chat-application-asp-net-jabber-ajax-wcf-comet-reverseajax-issues-faced
Here is finally wot i got and believe me its Awesome :)
1. create a new c# web application
2. Add a new page name it Services.aspx3. in the code file i.e. Services.aspx.cs add the following code.
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class Service : System.Web.UI.Page
{
public static string Delimiter = "|";
protected void Page_Load(object sender, EventArgs e)
{
Response.Buffer = false;
while (true)
{
Response.Write(Delimiter + DateTime.Now.ToString("HH:mm:ss.FFF"));
Response.Flush();
// Suspend the thread for 1/2 a second
System.Threading.Thread.Sleep(500);
}
// Yes I know we'll never get here, it's just hard not to include it!
Response.End();
}
}
4. Good Now add a html page say home.html and add this code to it.
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Comet AJAX Sample</title>
<script language="javascript">
function getData()
{
loadXMLDoc("Service.aspx");
}
var req = false;
function createRequest()
{
// branch for native XMLHttpRequest object
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;
}
}
}
}
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);
}
}
function processReqChange() {
if (req.readyState == 3) {
try
{
ProcessInput(req.responseText);
// At some (artibrary) length
// recycle the connection
if (req.responseText.length > 3000) {
lastDelimiterPosition = -1;
getData();
}
}
catch (e) {
alert(e.message);
}
}
}
var lastDelimiterPosition = -1;
function ProcessInput(input)
{
// Make a copy of the input
var text = input;
// Search for the last instance of the delimiter
var nextDelimiter =
text.indexOf('|', lastDelimiterPosition+1);
if (nextDelimiter != -1) {
// Pull out the latest message
var timeStamp = text.substring(nextDelimiter+1);
if (timeStamp.length > 0) {
lastDelimiterPosition = nextDelimiter;
ProcessTime(timeStamp);
}
}
}
function ProcessTime(time)
{
var out = document.getElementById('outputZone');
out.innerHTML = time;
}
</script>
</head>
<body onload="getData()">
<b>Server Time:</b> <span id="outputZone"></span>
</body>
</html>
5. And yes you have done it Now run your html page.
