That would probably sound weird but in spite of all FTP protocols's weaknesses and insecureness my boss still wants me to send files to the ftp server. It's an out-of window app with elevated trust. So I guess there is a way. I've tried to find any good examples but I found none. Would you guys help me here? Maybe I can use sockets and would able to make it work. They even agreed to re-config the server to use some other port.
You can use third-party components, such as our SecureBlackbox. If you have out-of-browser application, you should not be restricted to specific ports, so there should not be any problems in this aspect. Of course, only passive mode is supported in Silverlight, but again this is not a problem. And BTW SecureBlackbox supports both FTPS (FTP over SSL) and SFTP (SSH File Transfer Protocol) if you later decide to switch to secure communications.