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I'm making a web app that requires that I check to see if remote servers are online or not. When I run it from the command line, my page load goes up to a full 60s (for 8 entries, it will scale linearly with more).
I decided to go the route of pinging on the user's end. This way, I can load the page and just have them wait for the "server is online" data while browsing my content.
If anyone has the answer to the above question, or if they know a solution to keep my page loads fast, I'd definitely appreciate it.
I have found someone that accomplishes this with a very clever usage of the native Image object.
From their source, this is the main function (it has dependences on other parts of the source but you get the idea).
function Pinger_ping(ip, callback) {
if(!this.inUse) {
this.inUse = true;
this.callback = callback
this.ip = ip;
var _that = this;
this.img = new Image();
this.img.onload = function() {_that.good();};
this.img.onerror = function() {_that.good();};
this.start = new Date().getTime();
this.img.src = "http://" + ip;
this.timer = setTimeout(function() { _that.bad();}, 1500);
}
}
This works on all types of servers that I've tested (web servers, ftp servers, and game servers). It also works with ports. If anyone encounters a use case that fails, please post in the comments and I will update my answer.
Update: Previous link has been removed. If anyone finds or implements the above, please comment and I'll add it into the answer.
Update 2: #trante was nice enough to provide a jsFiddle.
http://jsfiddle.net/GSSCD/203/
Update 3: #Jonathon created a GitHub repo with the implementation.
https://github.com/jdfreder/pingjs
Update 4: It looks as if this implementation is no longer reliable. People are also reporting that Chrome no longer supports it all, throwing a net::ERR_NAME_NOT_RESOLVED error. If someone can verify an alternate solution I will put that as the accepted answer.
Ping is ICMP, but if there is any open TCP port on the remote server it could be achieved like this:
function ping(host, port, pong) {
var started = new Date().getTime();
var http = new XMLHttpRequest();
http.open("GET", "http://" + host + ":" + port, /*async*/true);
http.onreadystatechange = function() {
if (http.readyState == 4) {
var ended = new Date().getTime();
var milliseconds = ended - started;
if (pong != null) {
pong(milliseconds);
}
}
};
try {
http.send(null);
} catch(exception) {
// this is expected
}
}
you can try this:
put ping.html on the server with or without any content, on the javascript do same as below:
<script>
function ping(){
$.ajax({
url: 'ping.html',
success: function(result){
alert('reply');
},
error: function(result){
alert('timeout/error');
}
});
}
</script>
You can't directly "ping" in javascript.
There may be a few other ways:
Ajax
Using a java applet with isReachable
Writing a serverside script which pings and using AJAX to communicate to your serversidescript
You might also be able to ping in flash (actionscript)
You can't do regular ping in browser Javascript, but you can find out if remote server is alive by for example loading an image from the remote server. If loading fails -> server down.
You can even calculate the loading time by using onload-event. Here's an example how to use onload event.
Pitching in with a websocket solution...
function ping(ip, isUp, isDown) {
var ws = new WebSocket("ws://" + ip);
ws.onerror = function(e){
isUp();
ws = null;
};
setTimeout(function() {
if(ws != null) {
ws.close();
ws = null;
isDown();
}
},2000);
}
Update: this solution does not work anymore on major browsers, since the onerror callback is executed even if the host is a non-existent IP address.
To keep your requests fast, cache the server side results of the ping and update the ping file or database every couple of minutes(or however accurate you want it to be). You can use cron to run a shell command with your 8 pings and write the output into a file, the webserver will include this file into your view.
The problem with standard pings is they're ICMP, which a lot of places don't let through for security and traffic reasons. That might explain the failure.
Ruby prior to 1.9 had a TCP-based ping.rb, which will run with Ruby 1.9+. All you have to do is copy it from the 1.8.7 installation to somewhere else. I just confirmed that it would run by pinging my home router.
There are many crazy answers here and especially about CORS -
You could do an http HEAD request (like GET but without payload).
See https://ochronus.com/http-head-request-good-uses/
It does NOT need a preflight check, the confusion is because of an old version of the specification, see
Why does a cross-origin HEAD request need a preflight check?
So you could use the answer above which is using the jQuery library (didn't say it) but with
type: 'HEAD'
--->
<script>
function ping(){
$.ajax({
url: 'ping.html',
type: 'HEAD',
success: function(result){
alert('reply');
},
error: function(result){
alert('timeout/error');
}
});
}
</script>
Off course you can also use vanilla js or dojo or whatever ...
If what you are trying to see is whether the server "exists", you can use the following:
function isValidURL(url) {
var encodedURL = encodeURIComponent(url);
var isValid = false;
$.ajax({
url: "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20html%20where%20url%3D%22" + encodedURL + "%22&format=json",
type: "get",
async: false,
dataType: "json",
success: function(data) {
isValid = data.query.results != null;
},
error: function(){
isValid = false;
}
});
return isValid;
}
This will return a true/false indication whether the server exists.
If you want response time, a slight modification will do:
function ping(url) {
var encodedURL = encodeURIComponent(url);
var startDate = new Date();
var endDate = null;
$.ajax({
url: "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20html%20where%20url%3D%22" + encodedURL + "%22&format=json",
type: "get",
async: false,
dataType: "json",
success: function(data) {
if (data.query.results != null) {
endDate = new Date();
} else {
endDate = null;
}
},
error: function(){
endDate = null;
}
});
if (endDate == null) {
throw "Not responsive...";
}
return endDate.getTime() - startDate.getTime();
}
The usage is then trivial:
var isValid = isValidURL("http://example.com");
alert(isValid ? "Valid URL!!!" : "Damn...");
Or:
var responseInMillis = ping("example.com");
alert(responseInMillis);
const ping = (url, timeout = 6000) => {
return new Promise((resolve, reject) => {
const urlRule = new RegExp('(https?|ftp|file)://[-A-Za-z0-9+&##/%?=~_|!:,.;]+[-A-Za-z0-9+&##/%=~_|]');
if (!urlRule.test(url)) reject('invalid url');
try {
fetch(url)
.then(() => resolve(true))
.catch(() => resolve(false));
setTimeout(() => {
resolve(false);
}, timeout);
} catch (e) {
reject(e);
}
});
};
use like this:
ping('https://stackoverflow.com/')
.then(res=>console.log(res))
.catch(e=>console.log(e))
I don't know what version of Ruby you're running, but have you tried implementing ping for ruby instead of javascript? http://raa.ruby-lang.org/project/net-ping/
let webSite = 'https://google.com/'
https.get(webSite, function (res) {
// If you get here, you have a response.
// If you want, you can check the status code here to verify that it's `200` or some other `2xx`.
console.log(webSite + ' ' + res.statusCode)
}).on('error', function(e) {
// Here, an error occurred. Check `e` for the error.
console.log(e.code)
});;
if you run this with node it would console log 200 as long as google is not down.
You can run the DOS ping.exe command from javaScript using the folowing:
function ping(ip)
{
var input = "";
var WshShell = new ActiveXObject("WScript.Shell");
var oExec = WshShell.Exec("c:/windows/system32/ping.exe " + ip);
while (!oExec.StdOut.AtEndOfStream)
{
input += oExec.StdOut.ReadLine() + "<br />";
}
return input;
}
Is this what was asked for, or am i missing something?
just replace
file_get_contents
with
$ip = $_SERVER['xxx.xxx.xxx.xxx'];
exec("ping -n 4 $ip 2>&1", $output, $retval);
if ($retval != 0) {
echo "no!";
}
else{
echo "yes!";
}
It might be a lot easier than all that. If you want your page to load then check on the availability or content of some foreign page to trigger other web page activity, you could do it using only javascript and php like this.
yourpage.php
<?php
if (isset($_GET['urlget'])){
if ($_GET['urlget']!=''){
$foreignpage= file_get_contents('http://www.foreignpage.html');
// you could also use curl for more fancy internet queries or if http wrappers aren't active in your php.ini
// parse $foreignpage for data that indicates your page should proceed
echo $foreignpage; // or a portion of it as you parsed
exit(); // this is very important otherwise you'll get the contents of your own page returned back to you on each call
}
}
?>
<html>
mypage html content
...
<script>
var stopmelater= setInterval("getforeignurl('?urlget=doesntmatter')", 2000);
function getforeignurl(url){
var handle= browserspec();
handle.open('GET', url, false);
handle.send();
var returnedPageContents= handle.responseText;
// parse page contents for what your looking and trigger javascript events accordingly.
// use handle.open('GET', url, true) to allow javascript to continue executing. must provide a callback function to accept the page contents with handle.onreadystatechange()
}
function browserspec(){
if (window.XMLHttpRequest){
return new XMLHttpRequest();
}else{
return new ActiveXObject("Microsoft.XMLHTTP");
}
}
</script>
That should do it.
The triggered javascript should include clearInterval(stopmelater)
Let me know if that works for you
Jerry
You could try using PHP in your web page...something like this:
<html><body>
<form method="post" name="pingform" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<h1>Host to ping:</h1>
<input type="text" name="tgt_host" value='<?php echo $_POST['tgt_host']; ?>'><br>
<input type="submit" name="submit" value="Submit" >
</form></body>
</html>
<?php
$tgt_host = $_POST['tgt_host'];
$output = shell_exec('ping -c 10 '. $tgt_host.');
echo "<html><body style=\"background-color:#0080c0\">
<script type=\"text/javascript\" language=\"javascript\">alert(\"Ping Results: " . $output . ".\");</script>
</body></html>";
?>
This is not tested so it may have typos etc...but I am confident it would work. Could be improved too...
I am using ASP.Net Core with MVC for creating an app. I am using visual studio and IIS express currently.
Below is my current project structure:
*project directory
-wwwroot
-areas
-attachments
-controllers
-models
-views
I currently store images inside the attachments folder.
Previously I have written something like that inside my startup.cs
app.UseStaticFiles(new StaticFileOptions
{
FileProvider = new PhysicalFileProvider(
Path.Combine(Directory.GetCurrentDirectory(), "Attachments")),
RequestPath = "/Attachments"
});
I have also done something like this below:
appendImage(#Url.Content("~/Attachments/")+result.fileName);
I did this to display an image on my view. The image is displayed successfully.
What I am trying to achieve now is the on the UI allow the user to make a choice to delete the files inside that attachments folder
I tried the following code:
string contentRootPath = _hostingEnvironment.ContentRootPath;
string fullImagePath = Path.Combine(contentRootPath + "\\Attachments", currentItemToDelete.FileName);
if (System.IO.File.Exists(fullImagePath))
{
try{
System.IO.File.Delete(fullImagePath);
}catch(Exception e){
operationResult = "Attachment Path. Internal Server Error";
}
}
The execution does enter the if (System.IO.File.Exists(fullImagePath))
but it raises an exception when it reaches System.IO.File.Delete. The exception states that the file which resides in that path is being used by another process. And thus I cannot delete the file. The only process that is accessing the file is the web app I am creating/debugging at the same time. How do I prevent this exception from happening? Do I have to use other kind of code to delete the file ?
EDIT to include more details:
Inside my view(index.cshtml):
appendImage is a javascript function:
function appendImage(imgSrc) {
var imgElement = document.createElement("img");
imgElement.setAttribute('src', imgSrc);
if (imgSrc.includes(null)) {
imgElement.setAttribute('alt', '');
}
imgElement.setAttribute('id', "img-id");
var imgdiv = document.getElementById("div-for-image");
imgdiv.appendChild(imgElement);
}
That function is called below:
$.ajax({
url:'#Url.Action("GetDataForOneItem", "Item")',
type: "GET",
data: { id: rowData.id },
success: function (result) {
removeImage();
appendImage(#Url.Content("~/Attachments/")+result.fileName);
$("#edit-btn").attr("href", '/Item/EditItem?id=' + result.id);
},
error: function (xhr, status, error) {
}
});
After calling appendImage(); I change the href of a <a> tag. When the user clicks on the link, the user is directed to another page(edit.cshtml). In the page, the image which resides in that path is also being displayed with code like this:
<img src="#Url.Content("~/Attachments/"+Model.FileName)" alt="item image" />
In this new page(edit.cshtml), there is a delete button. Upon clicking the delete button, the execution of the program goes to the controller which is this controller function:
[HttpPost]
public string DeleteOneItem(int id)
{
//query the database to check if there is image for this item.
var currentItemToDelete = GetItemFromDBDateFormatted(id);
if (!string.IsNullOrEmpty(currentItemToDelete.FileName))
{
//delete the image from disk.
string contentRootPath = _hostingEnvironment.ContentRootPath;
string fullImagePath = Path.Combine(contentRootPath + "\\Attachments", currentItemToDelete.FileName);
if (System.IO.File.Exists(fullImagePath))
{
try
{
System.IO.File.Delete(fullImagePath);
}catch(Exception e)
{
}
}
}
return "";
}
EDIT to answer question:
Add in
System.GC.Collect();
System.GC.WaitForPendingFinalizers();
before system.io.file.delete
you can replace your C# method DeleteOneItem with this given code. may be it might work.
[HttpPost]
public string DeleteOneItem(int id)
{
//query the database to check if there is image for this item.
var currentItemToDelete = GetItemFromDBDateFormatted(id);
if (!string.IsNullOrEmpty(currentItemToDelete.FileName))
{
//delete the image from disk.
string contentRootPath = _hostingEnvironment.ContentRootPath;
string fullImagePath = Path.Combine(contentRootPath + "\\Attachments", currentItemToDelete.FileName);
if (System.IO.File.Exists(fullImagePath))
{
try
{
System.GC.Collect();
System.GC.WaitForPendingFinalizers();
System.IO.File.Delete(fullImagePath);
}
catch (Exception e) { }
}
}
return "";
}
try
{
System.GC.Collect();
System.GC.WaitForPendingFinalizers();
System.IO.File.Delete(fullImagePath);
}
catch(Exception e){
}
I am trying to write a cordova hybrid application test application on MobileFirst platform. In my challenge handler, I have included a code to send a login information to my authentication server using submitLoginForm() java script API.
I check using wireshark if any auth request to my authentication server is getting generated, but it does not.
Can you please help me identify the issue with my code?
I can see the alert until Inside handleChallenge3, but does not see the alert for Closing Challenge Handler.
One more thing, I am trying to use isCustomResponse() API just to see what kind of challenge/response is coming to my challenge handler, but it seems not to be getting triggered. Has this been deprecated in MobileFirst Platform 8?
Thanks
var LtpaAuthChallengeHandler = function(){
LtpaAuthChallengeHandler = WL.Client.createWLChallengeHandler("LtpaBasedSSO");
LtpaAuthChallengeHandler.isCustomResponse = function(transport) {
alert ("Inside isCustomResponse");
return true;
};
LtpaAuthChallengeHandler.loginResponse = function(response) {
alert ("Inside loginResponse");
LtpaAuthChallengeHandler.submitSuccess();
alert ("After loginResponse");
};
// handleFailure
LtpaAuthChallengeHandler.handleFailure = function(error) {
// WL.Logger.debug("Challenge Handler Failure!");
if(error.failure !== null && error.failure !== undefined){
alert(error.failure);
}
else {
alert("Unknown error");
}
};
LtpaAuthChallengeHandler.handleChallenge = function(challenge) {
alert ("Inside handleChallenge");
var msg = "";
alert ("Inside handleChallenge1");
var options = {
"headers" : {},
"parameters" : {
"username" : "admin",
"password" : "admin",
'login-form-type' : 'pwd'
}
};
alert ("Inside handleChallenge2");
var loginUrl = "<URI for forms based auth of auth server>";
alert ("Inside handleChallenge3");
LtpaAuthChallengeHandler.submitLoginForm (loginUrl, options, LtpaAuthChallengeHandler.loginResponse);
alert ("Closing Challenge Handler");
};
};
Once the credentials have been collected from the UI, use WLChallengeHandler's submitChallengeAnswer() to send an answer back to the security check.
isCustomResponse() is not applicable from MFP 8.0.
Refer to the Authentication and Security topic here.
Chrome extension Summary :
Get all the urls from google search from content script
Store the urls in an array and send it to background script
Background script receives array of urls and send POST request to server for all the urls one by one
Background script get the response for each url POST request
Now background script send the xhr.responseText to content script
content script "Receives" the response. responses are in json format
NEED HELP: now I need to compare the response if response [URLfulfills:true/false] is "true" i have add an icon next to url that responded back true and if it is false i have to set another false icon next to url that responded back "false"
Background.js
chrome.runtime.onMessage.addListener(
function(request, sender, sendResponse)
{
if (request.locs){
doSearchRequest(request.locs,sender.tab);
}
}
);
//Do the search request
function doSearchRequest(data,tab)
{
var length = Object.keys(data).length;
var sites,sitesUrl;
if (length <= 100){
sites = Object.getOwnPropertyNames(data).splice(0,50);
sitesUrl = JSON.stringify(sites);
doApiRequest(sites, tab);
if (length > 50){
sites = Object.getOwnPropertyNames(data).splice(50,50);
sitesUrl = JSON.stringify(sites);
doApiRequest(sites, tab);
}
return;
}
}
// Do an api request for multiple sites
var resp;
function doApiRequest(sitesarray, tab)
{
for(var i=0;i<sitesarray.length;i++){
var console = chrome.extension.getBackgroundPage().console;
var xhr = new XMLHttpRequest();
var p="domain="+sitesarray[i];
xhr.open("POST","https://api.xxx.com/api/", true);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.onreadystatechange = function()
{
if (xhr.readyState == 4 && xhr.status==200)
{
resp = JSON.parse(xhr.responseText);
chrome.tabs.sendMessage(tab.id, {data: resp}, function(response) {
console.log(status,resp);
});
}
}
xhr.send(p);
ContentScript.js
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
if (request.data){
data = request.data;
//Need to compare the received message [data] to access dom and
change icon according to response
.............
...........
}
});
//If document is ready, find the urls to check
$(document).ready(function() {
(function checkLoop() {
// Check if search results have link
var results = $('#res').find('a');
if ( $('.yyy').length != results.length) {
// Check urls
var locs = {};
$(results).each(function (i) {
var loc = getUrl($(this).attr('href'));
locs[loc] = loc;
});
if(Object.keys(locs).length > 0) {
// passes grabed urls to background page
chrome.runtime.sendMessage({locs: locs}, function(response) {});
}
}
setTimeout(checkLoop, 100);
})();
});
Json formatted API response
//my json formatted api response
{
"URLfulfills": false,
"Id": 16,
"url": {
"xid": 190,
"title": "www.facebook.com",
"description": "social site",
},
What you have to do is inspect the Google search result page and figure out where in the DOM you want to place your icon. Somewhere just next to the search result I would imagine. Additionally you have to request the local URL for the icon from your background script. I assume the icon is already in the same folder as your Chrome extension. Remember to make the icon accessible from the content script by specifying it in the manifest too.
To place the icon into the DOM (from the content script), use jQuery like so: $(someSearchResult).append('<img src=' + yourIconUrl + ' />');
If jQuery is not present, you could add it the old fashioned way, or just add jQuery to the DOM first.
I have a link: Hello.
When someone clicks the link I'd like to check via JavaScript if the page the href-attribute points to exists or not. If the page exists the browser redirects to that page ("www.example.com" in this example) but if the page doesn't exist the browser should redirect to another URL.
It depends on whether the page exists on the same domain or not. If you're trying to determine if a page on an external domain exists, it won't work – browser security prevents cross-domain calls (the same-origin policy).
If it is on the same domain however, you can use jQuery like Buh Buh suggested. Although I'd recommend doing a HEAD-request instead of the GET-request the default $.ajax() method does – the $.ajax() method will download the entire page. Doing a HEAD request will only return the headers and indicate whether the page exists (response codes 200 - 299) or not (response codes 400 - 499). Example:
$.ajax({
type: 'HEAD',
url: 'http://yoursite.com/page.html',
success: function() {
// page exists
},
error: function() {
// page does not exist
}
});
See also: http://api.jquery.com/jQuery.ajax/
A pretty good work around is to proxy. If you don't have access to a server side you can use YQL. Visit: http://developer.yahoo.com/yql/console/
From there you can do something like: select * from htmlstring where url="http://google.com". You can use the "REST query" they have on that page as a starting point for your code.
Here's some code that would accept a full URL and use YQL to detect if that page exists:
function isURLReal(fullyQualifiedURL) {
var URL = encodeURIComponent(fullyQualifiedURL),
dfd = $.Deferred(),
checkURLPromise = $.getJSON('http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20htmlstring%20where%20url%3D%22' + URL + '%22&format=json');
checkURLPromise
.done(function(response) {
// results should be null if the page 404s or the domain doesn't work
if (response.query.results) {
dfd.resolve(true);
} else {
dfd.reject(false);
}
})
.fail(function() {
dfd.reject('failed');
});
return dfd.promise();
}
// usage
isURLReal('http://google.com')
.done(function(result) {
// yes, or request succeded
})
.fail(function(result) {
// no, or request failed
});
Update August 2nd, 2017
It looks like Yahoo deprecated "select * from html", although "select * from htmlstring" does work.
Based on the documentation for XMLHttpRequest:
function returnStatus(req, status) {
//console.log(req);
if(status == 200) {
console.log("The url is available");
// send an event
}
else {
console.log("The url returned status code " + status);
// send a different event
}
}
function fetchStatus(address) {
var client = new XMLHttpRequest();
client.onreadystatechange = function() {
// in case of network errors this might not give reliable results
if(this.readyState == 4)
returnStatus(this, this.status);
}
client.open("HEAD", address);
client.send();
}
fetchStatus("/");
This will however only work for URLs within the same domain as the current URL. Do you want to be able to ping external services? If so, you could create a simple script on the server which does your job for you, and use javascript to call it.
If it is in the same domain, you can make a head request with the xmlhttprequest object [ajax] and check the status code.
If it is in another domain, make an xmlhttprequest to the server and have it make the call to see if it is up.
why not just create a custom 404 handler on the web server? this is probably the more "good-bear" way to do this.
$.ajax({
url: "http://something/whatever.docx",
method: "HEAD",
statusCode: {
404: function () {
alert('not found');
},
200: function() {
alert("foundfile exists");
}
}
});
If you are happy to use jQuery you could do something like this.
When the page loads make an ajax call for each link. Then just replace the href of all the links which fail.
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
<script type="text/javascript">
<!--
$.fn.checkPageExists = function(defaultUrl){
$.each(this, function(){
var $link = $(this);
$.ajax({
url: $link.attr("href"),
error: function(){
$link.attr("href", defaultUrl);
}
});
});
};
$(document).ready(function(){
$("a").checkPageExists("default.html");
});
//-->
</script>
You won't be able to use an ajax call to ping the website because of same-origin policy.
The best way to do it is to use an image and if you know the website you are calling has a favicon or some sort of icon to grab, you can just use an html image tag and use the onerror event.
Example:
function pingImgOnWebsite(url) {
var img = document.createElement('img');
img.style.visibility = 'hidden';
img.style.position = 'fixed';
img.src = url;
img.onerror = continueBtn; // What to do on error function
document.body.appendChild(img);
}
Another way to do this is is with PHP.
You could add
<?php
if (file_exists('/index.php'))
{
$url = '/index.php';
} else {
$url = '/notindex.php';
}
?>
And then
<a href="<?php echo $url; ?>Link</a>