Re: FtpWebRequest Passive Mode Problem

Are you sure that this isn't somehow related to the fact that both machines
are on the same LAN?

In fact, are you saying that the server and client are on the same machine?

I would have no idea how this would affect the situation.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
A watched clock never boils.

"Martin_Paul" <MartinPaul@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:7D91AD7D-3A56-46C1-8848-AD8103C90A95@xxxxxxxxxxxxxxxx
> Hi Kevin,
>
> Thanks again for the reply.
>
> In the situation I am describing it is not a proxy on the client end, but
> rather the server's control connection acting as a proxy. In this case
> this
> should be a TRANSPARENT proxy if the FtpWebRequest class followed RFC.
>
> There is a very easy way to show this problem under Windows:
>
> 1.) Get an eval copy of Serv-U FTPD
> 2.) Setup your server so that the domain runs on localhost
> 3.) Under the Advanced tab of the domain's settings tick "Enable Passive
> transfers, use IP:" and put a LAN ip in this box.
>
> What this means is that essentially serv-u listens on 127.0.0.1 but
> replies
> to the PASV command with 192.168.0.2 (or whatever). Now, obviously this
> should be fine for the data channel, it is after all the same site, BUT,
> connecting with FtpWebRequest will block this behaviour, which is highly
> irritating as I have many FTP servers where this type of masking takes
> place.
>
> As I have found no way of changing this I am resorting to using a raw
> Socket
> with an SslStream (which btw is a fine implementation), but it is a shame
> about FtpWebRequest and I have lodged this as a flaw on the Microsoft bug
> network.
>
> Thanks again,
>
> Martin
>
> "Kevin Spencer" wrote:
>
>> Sorry about the error in my assertion that the port is not necessarily
>> changed by the server. I haven't been into those RFCs in awhile!
>>
>> I did suspect a Proxy involved, however, and what you described would be
>> a
>> NAT/Proxy situation. In your case, it is further complicated by the fact
>> that apparently both your machine and the FTPD are on the same LAN. I
>> must
>> confess that I have not had to deal with this situation before; however,
>> upon some research into the FtpWebRequest class, and further reading of
>> the
>> RFC and some articles on NAT/Proxy configurations, I believe this can be
>> accounted for.
>>
>> Unfortunately, again, I have no means to test this for myself, so I can't
>> give you an authoritative answer. But my research indicates that you
>> should
>> investigate the FtpWebRequest.Proxy property, and the IWebProxy
>> interface,
>> as well as the topic of "Automatic Proxy Detection" in the .Net
>> Framwework
>> SDK.
>>
>> --
>> HTH,
>>
>> Kevin Spencer
>> Microsoft MVP
>> ..Net Developer
>> A watched clock never boils.
>>
>> "Martin_Paul" <MartinPaul@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> news:A0E6AA63-EDF2-4480-AA2F-550E914D4F48@xxxxxxxxxxxxxxxx
>> > Hi Kevin,
>> >
>> > When you send the FTP server the PASV command it will reply as follows
>> > (assuming the command is succesful):
>> >
>> > Entering Passive Mode (xxx,xxx,xxx,xxx,yy,yy)
>> >
>> > yy,yy is the port on which it is listening and the xxxs all indicate
>> > the
>> > IP
>> > address in split octet format, so therefore it is entirely possible for
>> > the
>> > IP address to be different to the control address. This is how the
>> > mechanism
>> > of server-to-server transfer is supported, as shown in RFC 959. This
>> > happens
>> > most commonly in 3 different situations:
>> >
>> > 1.) When using an ftpd behind a NAT
>> > 2.) When using an ftpd that employs a distributed architecture
>> > 3.) When using an ftpd that employs bouncers to route the traffic
>> > differently
>> >
>> > In all three of these circumstances I would *expect* a different data
>> > channel address to be sent back. Although I realise that this has been
>> > put
>> > in
>> > as a security feature, it is not RFC compliant or even remotely useful
>> > to
>> > give no way of overriding it.
>> >
>> > Any further help would be greatly appreciated and thanks for your time
>> > already!
>> >
>> > Martin
>> > "Kevin Spencer" wrote:
>> >
>> >> I've been using the new FtpWebRequest and FtpWebResponse now for many
>> >> months, and I haven't seen this happen. First of all, Passive mode
>> >> only
>> >> tells the server to send the *port* it will reply on, *not* the IP
>> >> address.
>> >> There is no reason why a server would reply on a different IP address.
>> >> I
>> >> suspect something kooky going on with your network. Are you using a
>> >> Proxy
>> >> by
>> >> any chance?
>> >>
>> >> --
>> >> HTH,
>> >>
>> >> Kevin Spencer
>> >> Microsoft MVP
>> >> ..Net Developer
>> >> A watched clock never boils.
>> >>
>> >> "Martin_Paul" <Martin_Paul@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> >> news:33C7E6E2-D386-40EB-AF70-D366AC33F050@xxxxxxxxxxxxxxxx
>> >> > Hi all,
>> >> >
>> >> > There appears to be a problem with the .NET 2.0 class FtpWebRequest
>> >> > in
>> >> > the
>> >> > following circumstance (an example):
>> >> >
>> >> > 1.) FTPD runs on port 21 on ip 192.168.0.2
>> >> > 2.) On issuing PASV command the data connection reply string gives
>> >> > IP
>> >> > !=
>> >> > 192.168.0.2
>> >> >
>> >> > So, when the data connection IP is different to the control
>> >> > connection
>> >> > IP
>> >> > the application throws a WebException helpfully informing me that
>> >> > this
>> >> > is
>> >> > the
>> >> > case.
>> >> >
>> >> > Is there any way to change this behaviour?
>> >> >
>> >> > Martin
>> >>
>> >>
>> >>
>>
>>
>>


.

Relevant Pages

  • Re: FtpWebRequest Passive Mode Problem
    ... Sorry about the error in my assertion that the port is not necessarily ... changed by the server. ... RFC and some articles on NAT/Proxy configurations, ... When using an ftpd behind a NAT ...
    (microsoft.public.dotnet.framework)
  • Re: smbclient timeout, file truncated / 9.1 Pro (was Re: libpopt.so.0 conflict...
    ... >and the OS/2 machines on the LAN. ... NETBEUI was invented to allow windows clients to use an OS/2 server. ... 9 buffer small read and write requests until the buffer is full ... Acknowledgment Timeout ...
    (alt.os.linux.suse)
  • Re: Indirect synchronization setup with no synchronizers on servers
    ... Replica Manager to be installed at all. ... trust any LAN, except the LAN where the file server is that stores my ... remote PCs have synchronizers but the server does not. ... There is no difference between a synchronizer operating on replicas ...
    (microsoft.public.access.replication)
  • Re: Possible to secure WEP?
    ... It doesn't have to be a "server". ... this IP cannot be in the same class C IP block as your own LAN. ... To keep it simple, my gateway router, ... Ethernet adapter Local Area Connection: ...
    (alt.internet.wireless)
  • Re: Can only connect to local RWW, over internet cannot
    ... OK, so now we know RWW works, and it is a function within RWW, the ability ... to 'Connect to Server' which is problematic, from inside the LAN. ... The 'Connect to server desktops' and 'Connect to my computer at work' ... RDP Proxy dynamically opens the connection to the requesting IP so at this ...
    (microsoft.public.windows.server.sbs)