Node.js - Recreating navigator.onLine

Question

I have a Node.js app. I am trying to write a utility app to do some network detection. I'm creating this app just to learn more about Node.

In this app, I want to see if a) my computer is online and b) if it can reach the internet. If I was doing this in the browser, I could use navigator.onLine, then attempt to reach a website. However, that's not an option in Node.

I looked at the OS module's networkInterfaces method, however, that doesn't seem to have what I need. For example, if you go to a Starbucks, you can be "online" but not actually reach the internet until you agree to the terms of service for their network. I've been testing this scenario by toggling airplane mode on my machine. Whether Airplane Mode is on or off, the networkInterfaces method returns the same thing.

How can I recreate the navigator.onLine functionality in Node?

Could something as simple as a `fetch` to a URL and then a check on the status code work? You shouldn't be able to get a `200` if you need to auth (in your example in Starbucks) because you won't actually connect to the page. Seems hacky but it may save some time. — James Gould, Jul 10 '18 at 11:41
This looks like a duplicate of Check for internet connectivity in NodeJs - https://stackoverflow.com/questions/15270902/check-for-internet-connectivity-in-nodejs — phuzi, Jul 12 '18 at 14:02
take a look at the repo: [is-online](https://github.com/sindresorhus/is-online) — ronapelbaum, Jul 12 '18 at 14:30

score 3 · Accepted Answer · answered Jul 18 '18 at 06:24

Here is the code to check whether the internet is available or not.

For this install the is-online module: npm i is-online

index.js:

const isOnline = require('is-online');

isOnline({
    timeout: 1000
}).then(online =>{
    if(online)
        console.log('Internet is available')
    else
        console.log('Internet is not available')
})

mshouman · Answer 2 · 2018-07-12T14:50:00.893

1

By calling onConnected and passing the call back function which will be called when the connection is established

const dns = require('dns');

function onConnected(callback){
    dns.resolve('www.google.com', function(err) {
        if (!err) callback();
    });
}

edited Jul 12 '18 at 14:50

answered Jul 12 '18 at 14:23

mshouman

374
2
12

score 0 · Answer 3 · answered Jul 12 '18 at 15:05

You can define navigator variable globally and set onLine param true or false.

const dns = require('dns');
const navigator = global.navigator = {onLine: false};

((navigator) => {
  const dns = require('dns');
  setInterval(() => {
    dns.resolve('www.google.com', 
                error => navigator.onLine = !error);
  }, 1000);
})(navigator);


setInterval(() => {
  console.log('Is online:', navigator.onLine ? 'yes' : 'no');
}, 1500);

score 0 · Answer 4 · answered Dec 21 '19 at 11:48

I'd go the route of

var exec = require('child_process').exec, child;
child = exec('ping -c 1 8.8.8.8', function(error, stdout, stderr){
     if(error !== null)
          console.log("Not available")
      else
          console.log("Available")
});

or trying to dns lookup

require('dns').lookupService('8.8.8.8', 53, function(err, hostname, service){
  console.log(hostname, service);
    // google-public-dns-a.google.com domain
});

Maybe trying to resolve a domain name

function checkNameResolution(cb) {
    require('dns').lookup('google.com',function(err) {
        if (err && err.code == "ENOTFOUND") {
            cb(false);
        } else {
            cb(true);
        }
    })
}

Really depends on your use case. Personally i'd spring for dnslookup of a higly avaliable address. But if your behind some sort of dns mask that resolves domains do localhost it might not be effective, which would in turn add the need to test name resolution also/instead. Combine those in a function like checkInternetConnection() and you'll be as good as it gets.

Node.js - Recreating navigator.onLine

4 Answers4