FTP (File Transfer Protocol) is a standard network protocol used to transfer files from one host to another over a TCP-based network, such as the Internet". Note that, FTP is a non-encrypted protocol. This means, all data (including user ID and password) is sent through the internet unencrypted! For that reason it is not allowed.
You can use secure SFTP and connect to transfer.gbar.dtu.dk to access the files in your Linux Home Directory using various applications:
1) FileZilla
2) For Windows users, the graphical client WinSCP can also be used.