Javascript or PHP: check if a host is reachable?

Question

PHP

How to use JavaScript or AJAX + PHP to check if the host exists or not? I need to check if the user has a web server running on the machine or not (localhost is available on a certain port) and if it is running, display one HTML, otherwise another.

Answer 1

Maybe try something like this?
var img = new Image();
$(img).load(function () {
alert('Хост доступен');
).error(function () {
alert('не загрузилась');
}).attr('src', 'ссылка на картинку на удалённом хосте');


Answer 2

fopen() if possible slowly, get_headers()/fsockopen() if necessary as quickly as possible

Answer 3

PHP: I don't know how to determine with Javascript. Unless you send an ajax request and see if it fails or not.
$handle = fsockopen('example.com', 80);
if ($handle !== false)
{
print('работает');
fclose($handle);
} else {
print('не работает');
}

Answer 4

php.net/manual/en/function.gethostbyname.php

Answer 5

Even if it works, it will fail. In the new opera, for example, the interaction of the localhost and external sites is tightly prohibited. There is even a special error for this, I don’t remember what it’s called.
Look towards java or flash.

Answer 6

Here is a javascript version. The idea is to use YQL .

Answer 7

Damn, somehow I didn’t think myself that you could just open a socket :) But we don’t know the ip address of a person - he can sit behind a nat.
In general, what is it for? There is a client application launched by the user. And there is a website. The site must check that the application is running and the socket is available and draw a button, otherwise some kind of inscription. By clicking on the button, the site should request data from the client and receive them. How is this implemented?