如果没有互联网连接，则持续加载

Question

I am currently developing a Online Controlled home but I have a problem with the internet connection checker.

I have this code to detect whether there is an internet connection or there is no internet connection.

$check = @fsockopen("www.google.com", 80); 
if($check){
    return true;
    fclose($check);
}else{
     return false;
     fclose($check);
}

but the problem is, when my Raspberry Pi don't have an internet connection then it continuously load the page forever.

the full script is here

<?php
    function checkConnection(){
        $check = @fsockopen("www.google.com", 80); 
        if($check){
            return true;
            fclose($check);
        }else{
             return false;
             fclose($check);
        }
    }
    if(checkConnection()==true){
        echo '[{"status":"success","result":"Internet Connection is Available"}]';
    }else{
        echo '[{"status":"fail","result":"No Internet Connection"}]';
    }
?>

Answer 1

Perhaps a small change in your function might enlighten the situation. For example:

   function checkConnection() {
         $fp = @fsockopen("www.google.com", 80, $errno, $errstr, 3); 
         if (!$fp) {
             return "$errstr ($errno)<br />\n";
         } else {
             return true;
         }
    }
    $con = checkConnection();
    if ($con===true) {
        echo json_encode( ["status" => "success","result" => "Internet Connection is Available"] );
    } else {
        //  should not be - No Internet Connection is Available
        echo json_encode( ["status" => "fail","result" => $con] );
    }

PS: Try it out in PHPFiddle and make sure to change the port from 80 to 83 for example. This of course does not mean that you don't have internet connection but that the host you reach at the specified port does not reply. Anyway it will simply fail the function and return the error message. Also please do notice the timeout limit of 3 seconds in fsocopen since you may alter it accordingly to your needs.

EDIT

A simpler and perhaps more accurate approach on what you are trying to do could be this.

   function checkConnection($hostname) {           
         $fp = gethostbyname($hostname);
         if (!inet_pton($fp)) {
            return json_encode( ["status" => "fail","result" => "Internet Connection is not Available or Host {$hostname} is wrong or does not exist."] ); 
         } else {
            return json_encode( ["status" => "success","result" => "Internet Connection is Available. Host {$hostname} exists and resolves to {$fp}"] );
         }
    }
    echo checkConnection('www.google.com');

You might want to check this comment in php.net on setting alternative options for gethostbyname .

Answer 2

fsockopen takes a timeout as the last param, which only applies while connection the socket

DNS lookup can be a factor too, AFAIK you can't control the timeout for that, unless if you're going to use gethostbyname() in that case you can use

putenv('RES_OPTIONS=retrans:1 retry:1 timeout:1 attempts:1');

to limit DNS lookup to 1s .

Based on your code here's how i would implement it.

function is_connected()
{
    //1. provide a timeout to your socket
    //2. use example.com as a domain, that's what it's made for (testing)
    $socket = @fsockopen("www.example.com", 80, $err_no, $err_str, 5);
    if ($socket){
        fclose($socket);
        return true; 
    }
    return false;
}

$success = json_encode(["status" => "success","result" => "Internet is Available"]);
$failure = json_encode(["status" => "fail","result" => "Internet is Unavailable"]);

echo is_connected() ? $success : $failure;