PHPMailer, SMTP连接服务器失败

我使用PHPMailer。但是当我上传到我的主机时，我得到错误SMTP连接()失败。

我的环境1. 服务器操作系统:CentOS 72. Web服务:XAMPP 5.6.83.PHPMailer: 5.2.4

这是我的代码:

<?php
    require_once('PHPMailer_old/class.phpmailer.php');
    try{
    $mail = new PHPMailer(true); // the true param means it will throw exceptions on errors, which we need to catch
    $mail->IsSMTP(); // telling the class to use SMTP
    $mail->SMTPDebug  = 1;                     // enables SMTP debug information (for testing)
    $mail->SMTPAuth   = true;                  // enable SMTP authentication
    $mail->SMTPSecure = "ssl";
    $mail->SMTPAutoTLS = false;        // close TLS
    $mail->Host       = "smtp.gmail.com";      // sets GMAIL as the SMTP server
    $mail->Port       = 465;                   // set the SMTP port for the GMAIL server
    $mail->Username   = "Test@gmail.com";  // GMAIL username
    $mail->Password   = "Test";  // GMAIpassword
    $mail->FromName = "Test Manager";
    $mail->From = "Test@gmail.com";
    $to = "Test@hotmail.com";
    $mail->AddAddress($to);
    $mail->Subject  = "First PHPMailer Message";
    $mail->AltBody    = "To view the message, please use an HTML compatible email viewer!";
    $mail->WordWrap   = 80;
    $body = "success!";
    $mail->MsgHTML($body);
    $mail->IsHTML(true);
    $mail->Send();
    echo "Message has been sent.";
    }catch(phpmailerException $e){
        echo "Sending Failed";
        echo $e -> errorMessage();
    }
    ?>

web中的错误信息:SMTP ->错误:连接服务器失败:(0)send FailedSMTP Error: Could not connect to SMTP host.