Python – FTP upload file works manually, but fails using Python ftplib

I installed vsFTP in a Debian box. When manually upload file using ftp command, it's ok. i.e, the following session works:

john@myhost:~$ ftp xxx.xxx.xxx.xxx 5111
Connected to xxx.xxx.xxx.xxx.
220 Hello,Welcom to my FTP server.
Name (xxx.xxx.xxx.xxx:john): ftpuser
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> put st.zip
local: st.zip remote: st.zip
200 PORT command successful. Consider using PASV.
150 Ok to send data.
226 File receive OK.
12773 bytes sent in 0.00 secs (277191.8 kB/s)
ftp> 221 Goodbye.

(Please noted that as above, I configured vsFTP server to use a non-default port,e.g 5111 for some reason)

Now when I write a script in python to upload file programmatically, it failed. the error says 'time out', as the following session shows:

john@myhost:~$ ipython
Python 2.5.2 (r252:60911, Jan 24 2010, 14:53:14) 
Type "copyright", "credits" or "license" for more information.

IPython 0.8.4 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object'. ?object also works, ?? prints more.

In [1]: import ftplib

In [2]: ftp=ftplib.FTP()                                                    

In [3]: ftp.connect('xxx.xxx.xxx.xxx','5111')                                
Out[3]: "220 Hello,Welcom to my FTP server."

In [4]: ftp.login('ftpuser','ftpuser')                              
Out[4]: '230 Login successful.'

In [5]: f=open('st.zip','rb')                              

In [6]: ftp.storbinary('STOR %s' % 'my_ftp_file.zip', f)                            
---------------------------------------------------------------------------
error                                     Traceback (most recent call last)

...

/usr/lib/python2.5/ftplib.pyc in ntransfercmd(self, cmd, rest)
    322             af, socktype, proto, canon, sa = socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM)[0]
    323             conn = socket.socket(af, socktype, proto)
--> 324             conn.connect(sa)
    325             if rest is not None:
    326                 self.sendcmd("REST %s" % rest)

/usr/lib/python2.5/socket.pyc in connect(self, *args)

error: (110, 'Connection timed out')

I guess there is some wrong config in my vsFTP server, but cannot figure it out. Anyone can help ?

my vsFTP config is:

listen=YES

connect_from_port_20=YES
listen_port=5111
ftp_data_port=5110

# Passive FTP mode allowed
pasv_enable=YES
pasv_min_port=5300
pasv_max_port=5400

max_per_ip=2