Archived from groups: microsoft.public.broadbandnet.hardware (
More info?)
The best thing to do (IMHO) is to either use port 21 (there are reasons why
you might not want to though, understandably), or set up passive mode
transfers on your ftp server.
It's too bad FTP isn't NAT friendly.
--
Jason Tsang - Microsoft MVP
Find out about the MS MVP Program -
http://mvp.support.microsoft.com/default.aspx
<anonymous@discussions.microsoft.com> wrote in message
news:194d01c4bca7$eeda22d0$a601280a@phx.gbl...
> Yes, I doubt the client is behind a firewall though I
> really don't know.
>
> So was I right about the problem? Because what you meant by
>
>>the router doesn't know what port to forward back to the
> ftp client.
>
> is refering the problem on the client side, but what I said
> was what happened on the server side.
>
> Is there a way to work this out besides from setting the
> port to 21 if the client is behind a firewall? 'cause you
> will never know what kind of network the client is
> connecting from.
> BTW, even if the server is not behind a NAT but with a
> non-standard port, the client will still have problem
> establishing the ftp-data socket! because the NAT on the
> client side will not check the non-standard port as you said!
>
> It shouldn't be that complicated, shouldn't it?
>
> thanks
>
> Joseph
>
>
>>-----Original Message-----
>>Ok I've re-read your first posting.
>>
>>The problem lies with the FTP client (whoever is
> connecting to you).
>>
>>Are you sure the person connecting to you isn't behind a
> shared connection
>>or firewall.
>>
>>--
>>Jason Tsang - Microsoft MVP
>>
>>Find out about the MS MVP Program -
>>http://mvp.support.microsoft.com/default.aspx
>>
>><anonymous@discussions.microsoft.com> wrote in message
>>news:211e01c4bc7c$c070c8c0$a301280a@phx.gbl...
>>> First, thanks for your kindly reply, but..I still don't
>>> uderstand. Why does the router on the server side needs to
>>> know which port to listen on? It's the server that is
>>> trying to connect to some other machine. Besides that, the
>>> port is actually choosen by the ftp client under active
>>> mode, so all what the ftp server has to do is connect to
>>> the socket that's listening on the client's machine.
>>>
>>> Please correct me if I was wrong.
>>>
>>> p.s.
>>> Let's clearify the situation again:
>>> The server is behind NAT(mn-500) and the client is on the
>>> internet with real IP address and no firewall. Problem
>>> occus when the two machines are trying to establish the
>>> ftp-port connection.
>>>
>>> Thank you.
>>>
>>> Joseph
>>>
>>>>-----Original Message-----
>>>>The router doesn't know which port to listen on (that's
>>> choosen by the ftp
>>>>server). That's where the problem lies (this is under
>>> the assumption that
>>>>you are connecting to an FTP server on the internet, it
>>> does not apply when
>>>>you connect to an FTP server within your own LAN).
>>>>
>>>>--
>>>>Jason Tsang - Microsoft MVP
>>>>
>>>>Find out about the MS MVP Program -
>>>>http://mvp.support.microsoft.com/default.aspx
>>>>
>>>>"Joseph" <anonymous@discussions.microsoft.com> wrote in
>>> message
>>>>news:18a201c4bc47$3ed93a20$a501280a@phx.gbl...
>>>>> >Most routers get around this by having an Application
>>>>> Layer Gateway (ALG) to sniff FTP connections
>>>>>>on port 21. This is done so that the router can then
>>>>> redirect the
>>>>>>communications port (randomly assigned by the server you
>>>>> are connecting to)
>>>>>>back to the ftp client (i.e. you).
>>>>>
>>>>> I am pretty sure that under active mode when establishing
>>>>> the ftp-data socket, client is actually the one that is
>>>>> listening. So there's no reason for the router to block
>>>>> this connection from inside of its network. It's just a
>>>>> normal connection going outside.
>>>>> This is the part I don't understand.
>>>>>
>>>>>
>>>>>>Your best bet is to use passive mode for FTP. Of course,
>>>>> you'll need to
>>>>>>make sure that your FTP server that you are connecting to
>>>>> is configured
>>>>>>properly for passive mode.
>>>>>>
>>>>>
>>>>> Yes, I tried passive mode with port forwarding, but I
>>>>> found out that the server would give its local ip address
>>>>> instead(i.e. 192.168.1.5). Therefore, when the client
>>>>> receive this IP there's no way it can find the rout to the
>>>>> server( client is out side of NAT).
>>>>>
>>>>> Thank you.
>>>>>
>>>>> Joseph
>>>>
>>>>
>>>>.
>>>>
>>
>>
>>.
>>
Facebook
Twitter
Instagram