LIST and RETR FTP commands fails if 6tunnel is used as ftp proxy

[raghu328568]

ftp.connect("fdf8:f535:82e4::52", 21)
'220 pyftpdlib 1.5.6 ready.'
ftp.login('ftp','password')
'230 Login successful.'
ftp.cwd('/RRHSIM6/logfiles/Full')
'250 "/RRHSIM6/logfiles/Full" is the current directory.'
ftp.retrlines('LIST')
Traceback (most recent call last):
File "", line 1, in
File "/usr/lib64/python2.7/ftplib.py", line 437, in retrlines
conn = self.transfercmd(cmd)
File "/usr/lib64/python2.7/ftplib.py", line 376, in transfercmd
return self.ntransfercmd(cmd, rest)[0]
File "/usr/lib64/python2.7/ftplib.py", line 335, in ntransfercmd
conn = socket.create_connection((host, port), self.timeout)
File "/usr/lib64/python2.7/socket.py", line 571, in create_connection
raise err
socket.error: [Errno 111] Connection refused
exit

proxy side:
[root@ruproxy-6 /]# ./6tunnel -6 -l fdf8:f535:82e4::52 21 -4 169.254.6.2 21 -L 20 -v
resolving 169.254.6.2
resolved to 169.254.6.2
resolving local address fdf8:f535:82e4::52
resolved to fdf8:f535:82e4::52
local: fdf8:f535:82e4::52,21; remote: 169.254.6.2,21; source: default
<4> connection from fdf8:f535:82e4:0:800::,51902 (no. 1)
<4> connected to 169.254.6.2,21

<4> connection closed
child process exited