If you are unable to connect to FTP server in Ubuntu (Linux), then the most easy way is to use Mozilla FireFox FireFTP. You don’t need to install any separate software for uploading and downloading on your FTP server. Simply install this addon in your FireFox, and you will be able to upload and download files from your FTP server.
From some of its great features, the amazing feature of FireFTP is that it is Cross-Platform. It works on Windows, Mac OS X, Linux. As it is an addon of FireFox, so there is no worry of its availability on different platforms. The other good feature is that it is Free.