Use ftp to obtain source code.

I am following a linux command line book to learning compiling.

    [me@linuxbox src]$ ftp ftp.gnu.org 
    Connected to ftp.gnu.org. 
    220 GNU FTP server ready.

I tried and it report error

    $ ftp ftp://ftp.gnu.org/
    -bash: ftp: command not found

and

    $ ftp 
    -bash: ftp: command not found

How to solve the problem?