The connection was reset in gcm

I am using this code to send push notification to device

$registatoin_ids=array("DEVICE REG ID");
$message = array("product" => "shirt");
define("GOOGLE_API_KEY", "API KEY");
$url = 'https://android.googleapis.com/gcm/send';
$fields = array(
    'registration_ids' => $registatoin_ids,
    'data' => $message,
);
$headers = array(
    'Authorization:key=' . GOOGLE_API_KEY,
    'Content-Type:application/json'
);
$ch=curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
$result = curl_exec($ch);
if ($result === FALSE) {
    die('Curl failed: ' . curl_error($ch));
}
curl_close($ch);
echo $result;

      

        
        
        
      

    

But when I try to submit, I get a "Connection has been reset" error in the browser. What could be causing this problem?

Screenshot:

Ps: Curl is running on my server.