title: Calculate file checksum in FTP server using Apache FtpClient
body: <p>I am using FtpClient of Apache Commons Net to upload videos to FTP server. To check if the file has really been successfully transferred, I want to calculate the checksum of remote file, but unfortunately I found there is no related API I could use. 
  <p>
  My question is: <strong>Whether there is a need to calculate file checksum in ftp server?</strong> <br>If the answer is yes, how to get checksum in FtpClient?
  <br>If the answer is no, how do FtpClient know if the file has really been successfully and completely transferred?
  <p></p>