FTP zip upload is corrupted sometimes

Question

I wrote a code for saving few images in a file and later compressing that file and uploading to an ftp server. When I download that from server, few files are fine and few f

Answer 1

Be sure to transfer files in BINARY_FILE_TYPE. Maybe ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE); returns false?

By the way, if you transfer a zip in ASCII-mode, this will almost surely result corrupted.

Answer 2

See also Is java.io.BufferedOutputStream safe to use? which shows how out.close() might hide an IOException. Solution is to do an explicit out.flush() before out.close.

Also, whatever is retrieving the file from your FTP server, is that also using BINARY mode to retrieve?