FTP data port

All,

I know that by default FTP uses port 21 as the command port and port 20 as
the data port.
I am trying to send data to an external server via an As400 FTP connection
(OS/400 V4.5). 

Unfortunately for me they have certain restrictions. These being :-

a. The command port must be port 10021
b. The data port must be port 10020
c. Passive mode must be OFF.
d. PORT mode must be ON.

Now I can connect to the server 192.168.36.2 10021 which allows me to
connect using command port 10021.

>From this I can run the commands
SENDPASV 0      - turn off passive mode
SENDPORT 1      - turn on port mode

but as soon as I try to put or get data the error message
'425 can't build data connection: connection timed out'  appears.

The connection is going through a firewall , which has been examined , and
all that is shown is the initial connection over port 10021. No mention of
port 20 or 10020 appears.

I think this may have something to do with the data port 10020 not being
correctly set on the AS400.But how do I do this ?

Looking at WRKTCPSTS option 3 shows my local port 21 in the list at a listen
status , but no port 20.

When the connection is active , remote port 10021 is displayed against the
customers IP address , but no port 20 or 10020.

Is this the problem? If so how do I correct this and are there any security
issues that I should be made aware of if port 20 or port 10020 are open?


Regards

Steven Gray
Senior Analyst
ArvalPHH

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