Yii2 FTP Client for Yii 2 extension creates empty files when transferring?

Question

Yii

FTP Client for Yii 2 extension https://github.com/yii2mod/yii2-ftp
Method $ftp->putAll($source_directory, $target_directory);
Returns PHP Warning - yii\base\ErrorException
ftp_put(): Failed to establish connection.
In fact, a 0kb file is created on ftp.