not able to connect to sms gateway using curl in php

I have a website done in codeigniter php, where I want to send sms to user, the plain php curl is working fine in phpsanbox or on my local, now I added it to my codeigniter model like below:

public function sendOtptoCustomer($mobile,$customerMessage,$temp_id){
    $url = "http://dstri.connectbind.com:8443/sendsms/bulksms?username=xxxxx&password=xxxxx&type=0&dlr=1&destination=".$mobile."&source=xxxx&message=".$customerMessage."&entityid=xxxx&tempid=".$temp_id;

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); 

    $response = curl_exec($ch);


    if (curl_errno($ch)) {
        $error_message = curl_error($ch);
        var_dump($error_message); 
    } 

    curl_close($ch);
}

Here i am getting the following error:

string(72), failed to connect to dstri.connectbind.com port 8443 connection refused

Can anyone please tell me what could be wrong in here, thanks in advance