on-line
v0.1.1
Published
Check if the internet connection is up
Downloads
13
Readme
on-line
Check if the internet connection is up
Works in Node.js.
In the browser you have navigator.onLine
, but it's useless as it only tells you if there's a local connection, and not whether the internet is accessible.
Install
$ npm install --save on-line
Usage
The basic use
var isOnline = require('on-line');
isOnline(function(err, online) {
console.log(online);
// => true
});
Custom options
var isOnline = require('on-line');
isOnline({ timeout: 1000, server: '199.7.83.42' }, function(err, online) {
console.log(online);
// => true
});
Node API
isOnline([options,]callback)
options
Optional
Type: object
timeout
Type: number
Milliseconds to wait for a server to send response.
server
Type: string
Testing server.
callback(error, online)
Required
Type: function
error
is there only by Node.js convention and is always null
.
How it works
In node, we first contact one of the thirteen root servers and ask them to direct us to the servers which host the <root>
zone (Which they are themselves). If the server answers, we return an online status.
If no satisfying answer is given within one second, we return an offline status. In the rare case where an firewall intercepts the packet and answers it on its behalf, a second check is run which tries to connect to a series of popular web sites on port 80. If one of these connects, we return online, otherwise offline status.
In the browser, a sophisticated check like in node is not possible because DNS and sockets are abstracted away. We use a check which requests an uncached favicon.ico
on a series of popular websites. If one of this checks succeeds, we return online status. If all the requests fail, we return offline status.
Thanks
License
MIT