Determine in php script if connected to internet?

Question

How can I check if I'm connected to the internet from my PHP script which is running on my dev machine?

I run the script to download a set of files (which may or may not exist) using wget. If I try the download without being connected, wget proceeds to the next one thinking the file is not present.

score 87 · Accepted Answer · edited Oct 13 '16 at 08:30

87

<?php
function is_connected()
{
    $connected = @fsockopen("www.example.com", 80); 
                                        //website, port  (try 80 or 443)
    if ($connected){
        $is_conn = true; //action when connected
        fclose($connected);
    }else{
        $is_conn = false; //action in connection failure
    }
    return $is_conn;

}
?>

edited Oct 13 '16 at 08:30

Thamaraiselvam

6,391
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answered Feb 01 '11 at 08:37

Alfred

19,306
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3

+ Nice answer be someone else might think `[80|443]` would switch between any of the ports ... :) – Baba Apr 04 '13 at 21:23
2

Based on [this](https://www.quora.com/Downtime/What-is-the-most-reliable-website-in-terms-of-uptime) post, it would probably make a lot of sense to use example.com as the "www.some_domain.com" of the answer. – nzn Feb 02 '16 at 19:16

score 9 · Answer 2 · answered Feb 01 '11 at 08:37

9

You can always ping good 'ol trusty google:

$response = null;
system("ping -c 1 google.com", $response);
if($response == 0)
{
    // this means you are connected
}

answered Feb 01 '11 at 08:37

Gabi Purcaru

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This is quite reliable, but keep in mind that "ICMP works != TCP works" (what with firewalls, NATs and whatnot), and even "TCP works != HTTP works" (transparent proxies etc.). – Piskvor left the building Feb 01 '11 at 09:26

score 8 · Answer 3 · answered Jan 16 '15 at 20:08

This code was failing in laravel 4.2 php framework with an internal server 500 error:

<?php
     function is_connected()
     {
       $connected = @fsockopen("www.some_domain.com", 80); 
        //website, port  (try 80 or 443)
       if ($connected){
          $is_conn = true; //action when connected
          fclose($connected);
       }else{
         $is_conn = false; //action in connection failure
       }
      return $is_conn;
    }
?>

Which I didn't want to stress myself to figure that out, hence I tried this code and it worked for me:

function is_connected()
{
  $connected = fopen("http://www.google.com:80/","r");
  if($connected)
  {
     return true;
  } else {
   return false;
  }

}

Please note that: This is based upon the assumption that the connection to google.com is less prone to failure.

Nice alternative! This also requires `allow_url_fopen = On` in php.ini — zanderwar, Aug 06 '19 at 05:27
In my tests fopen is twice slower than the fsockopen alternative. Also, it would look nicer this syntax instead of an ugly if() with return true/false: return (bool) fopen("http://www.google.com:80/","r"); — aFeijo, Jan 15 '20 at 14:02

score 4 · Answer 4 · answered Feb 17 '16 at 23:01

The accepted answer did not work for me. When the internet was disconnected it threw a php error. So I used it with a little modification which is below:

if(!$sock = @fsockopen('www.google.com', 80))
{
    echo 'Not Connected';
}
else
{
echo 'Connected';
}

score 3 · Answer 5 · answered Feb 01 '11 at 08:44

Why don't you fetch the return code from wget to determine whether or not the download was successful? The list of possible values can be found at wget exit status.

On the other hand, you could use php's curl functions as well, then you can do all error tracking from within PHP.

score 1 · Answer 6 · answered Feb 01 '11 at 08:38

There are various factors that determine internet connection. The interface state, for example. But, regardles of those, due to the nature of the net, proper configuration does not meen you have a working connection.

So the best way is to try to download a file that you’re certain that exists. If you succeed, you may follow to next steps. If not, retry once and then fail.

Try to pick one at the destination host. If it’s not possible, choose some major website like google or yahoo.

Finally, just try checking the error code returned by wget. I bet those are different for 404-s and timeouts. You can use third parameter in exec call:

string exec ( string $command [, array &$output [, int &$return_var ]] )

score 1 · Answer 7 · answered May 31 '18 at 11:14

1

/*
 * Usage: is_connected('www.google.com')
 */
function is_connected($addr)
  {
    if (!$socket = @fsockopen($addr, 80, $num, $error, 5)) {
      echo "OFF";
    } else {
      echo "ON";
    }
  }

answered May 31 '18 at 11:14

cagcak

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score 1 · Answer 8 · answered Sep 18 '20 at 11:18

1

Also note that fopen and fsockopen are different. fsockopen opens a socket depending on the protocol prefix. fopen opens a file or something else e.g file over HTTP, or a stream filter or something etc. Ultimately this affects the execution time.

answered Sep 18 '20 at 11:18

John Katieno

39
5

score 0 · Answer 9 · answered Jan 14 '17 at 09:10

This function handles what you need

function isConnected()
{
    // use 80 for http or 443 for https protocol
    $connected = @fsockopen("www.example.com", 80);
    if ($connected){
        fclose($connected);
        return true; 
    }
    return false;
}

score 0 · Answer 10 · answered Feb 01 '11 at 08:35

0

You could ping to a popular site or to the site you're wgetting from (like www.google.nl) then parse the result to see if you can connect to it.

<?php
$ip = '127.0.0.1'; //some ip
exec("ping -n 4 $ip 2>&1", $output, $retval);
if ($retval != 0) { 
echo "no!"; 
} 
else 
{ 
echo "yes!"; }
?>

answered Feb 01 '11 at 08:35

Roy T.

8,981
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Except don't actually do it by IP address. – Ignacio Vazquez-Abrams Feb 01 '11 at 08:39
And why not use some IP? That's exactly what happens behind the scenes using some a domain anyway. – killstreet Dec 07 '16 at 20:04
@killstreet using a FQDN is smarter coding, that way you can update the DNS without having to update your code – zanderwar Aug 06 '19 at 05:29

Dietrich Epp · Answer 11 · 2013-07-26T20:28:10.873

Just check the result of wget. A status code of 4 indicates a network problem, a status code of 8 indicates a server error (such as a 404). This only works if you call wget for each file in sequence, rather than once for all the files.

You can also use libcurl with PHP, instead of calling wget. Something like:

foreach (...) {
    $c = curl_init($url);
    $f = fopen($filepath, "w")
    curl_setopt($c, CURLOPT_FILE, $f);
    curl_setopt($c, CURLOPT_HEADER, 0);
    if (curl_exec($c)) {
        if (curl_getinfo($c, CURLINFO_HTTP_CODE) == 200) {
            // success
        } else {
            // 404 or something, delete file
            unlink($filepath);
        }
    } else {
        // network error or server down
        break; // abort
    }
    curl_close($c);
}

Determine in php script if connected to internet?

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