Download data from FTP on Android

I’m trying to get json data from the ftp server using FtpWebRequest. Everything works fine on standalone windows. Anync downloading method works as well. But when I try to do the same on Android I get SocketException : Access denied. Why could it be and how to fix it? I use the same credentials.

I’ve found out, that the problem dissapears if I set Development build On. But I need it to work into release build too and I can’t find any permission difference or something like that between these options.

http://botsitgames.com/unity-engine-ftp-uzerinden-dosya-cekme/