Underfined offset: -1 ErrorException 在尝试连接到远程服务器时从 phpseclib 抛出的含义是什么？

Question

I am trying to login to a remote server using phpseclib Net_SSH2->login() function. I am getting a connection timeout error, therefore I added $ssh->getLastError() to get a more clear error message but all I get is

exception 'ErrorException' with message 'Undefined offset: -1'

along with the stack trace. I am wondering what does Undefined offset mean here and most importantly what does the number -1 refer to? Thanks!!

Here's my code:

$ssh = new \Net_SSH2('host.address');
$key = new \Crypt_RSA();
$key->setPassword('');
$key->loadKey(file_get_contents('keyfile.ppk'));
try
{
    if ($login = $ssh->login('username', $key))
    {
        \Log::error('Success');
        \Log::info($login);
        \Log::error('-----------------------');

    } else {
        \Log::error('Failed');
        \Log::error($ssh->getErrors());
        \Log::error($ssh->getLastError());
        \Log::error('-----------------------');
     }

 } catch(\Exception $e) {
     \Log::error('Exception');
     \Log::error($ssh->getErrors());
     \Log::error($ssh->getLastError());
     \Log::error('-----------------------');
 }

Answer 1

I figured that the exception is being thrown from inside the login function of php seclib. The reason was that I had to white-list my IP address on the target server, so it was the attempt to connect to the target server that was failing due to a timeout.