我正在尝试获取一个PHP脚本以连接到服务器，以便可以将文件上传到服务器。当我尝试以下代码尝试连接到服务器时，出现以下错误：
Warning: ssh2_connect(): Unable to connect to XXXX.com on port 22 in /var/www/html/XXXX.php on line 21
Warning: ssh2_connect(): Unable to connect to XXXX.com in /var/www/html/XXXX.php on line 21
Could not connect to server.
这里的问题是什么，我该如何解决？
我从中发送请求的服务器在Cent OS 7（Apache 2.4.6）上运行，而接收请求的服务器在Unix（Apache 2.2.15）上运行。
ini_set('display_errors','On');
define("dir",'xxxxxx');
define("quickCheckusername","xxxx");
define("quickCheckPassword","xxxxx");
define("quickCheckServer","xxxxx");
// Approach 1
// if(!is_readable(dir)) {
// echo ("$file is not readable");
// exit;
// }
// //scan directory for files
// $files = scandir(dir);
// //for each of the files found we want to process them by
// //uploading them to quickcheck
// //first connect to server
// $connection = ssh2_connect(quickCheckServer);
// if (!$connection) {
// echo("Could not connect to server.");
// }
// //login
// ssh2_auth_password($connection,quickCheckusername,quickCheckPassword);
// if (!ssh2_auth_password($connection,'name','password')) {
// echo("Could not authenticate into server.");
// }
// $sftp = ssh2_sftp($connection);
// //------------------------Approach 2------------------------------------------------------
// $connection = ftp_connect(quickCheckServer);
// if (@ftp_login($connection,quickCheckPassword))
// {
// echo "Connection established.";
// }
// else
// {
// echo "Couldn't establish a connection.";
// }
// ftp_close($connection);
// //-------------Approach 3--------------------------------------------------
// set up basic ssl connection
// $conn_id = ftp_ssl_connect(quickCheckServer);
// // login with username and password
// $login_result = ftp_login($conn_id,quickCheckPassword);
// if (!$login_result) {
// // PHP will already have raised an E_WARNING level message in this case
// die("can't login");
// }
// echo ftp_pwd($conn_id); // /
// // close the ssl connection
// ftp_close($conn_id);
我也查看了How to install phpseclib?，但我认为我不可能在Cent OS 7中执行此操作。因为我需要安装apt-get并根据 https://unix.stackexchange.com/questions/369141/is-it-possible-to-run-apt-get-in-centos-if-yes-how我不能。