Computer A (assumed that ip is 44.44.44.44)can ftp the host 130.89.148.12.

ftp 130.89.148.12
Connected to 130.89.148.12.
220 ftp.debian.org FTP server
Name (130.89.148.12:debian8): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.

Computer B (my local pc) can not ftp the host 130.89.148.12. Let's build a ssh tunnel with ssh command this way:

ssh -L -f -N localhost:2121:130.89.148.12:21   [email protected]

The ssh tunnel between my local pc and Computer A (44.44.44.44) was connected after password to login into 44.44.44.44.
Then to input the command on my local pc console:

ftp  localhost:2121
ftp: localhost:2121: Name or service not known

What is the matter with my ssh tunnel?

Think to chexum, the right ftp command is ftp localhost 2121 But new problem.