"Allen Chen [MSFT]" wrote:

> Hi Morris,
>
> >I have a textbox fields on an aspx page that the user fills in then when
> >they click on submit the fields get emailed to me.
>
> >How do I get the user's IP address?  I don't have any sign-in requirements.
>
> To get a client IP usually we can use Request.UserHostAddress. However, if
> the client is under a proxy the IP got by Request.UserHostAddress probably
> is not the real one of the client.
>
> For some proxies you probably can check
> Request.ServerVariables["HTTP_X_FORWARDED_FOR"]. If it's not null it
> contains the IP of client.
>
> For other proxies that intentionally hide the IP of client it's hard to
> know the real IP of client. A possible solution is to use ActiveX.
>
> I have a question BTW. Why you need to know client's IP to send email?
>
> Regards,
> Allen Chen
> Microsoft Online Support
>
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"Allen Chen [MSFT]" wrote:

> Hi Morris,
>
> >I don't need the IP to send the email.  I have a page with fields(name,
> >phone, email, etc) that the user fills then clicks submit to download our
> >demo.  This sends me an email with the data from the fields.  Normally the
> >user does not enter the data (we do not force them to) so automatically
> >getting their IP or Remote Host I can see if there were duplicate
> requests,
> >etc.  My previous website using front page I was able to get this field
> and
> >hoping I can get similar data from my new asp.net website.
>
> From your description you want to restrict a user to download a file only
> once, right? If so you have several options:
>
> 1. Check user's IP. The way to do so in ASP.NET is mentioned in my previous
> post. Please note, due to the existing of proxy, the IP you get may not be
> the real one of client. In addition, the way to bind to client's IP doesn't
> mean one user can only download a file only once. User's IP may change in
> many cases, such as accessing to the internet by dialing ISP to request for
> IP.
>
>
> 2. Check the MAC of network adapter of user's machine. This option is
> better than checking IP because in most cases changing network adapter is
> much more expensive. You can also check other hardware related information.
> However, the difficulty is, we cannot get these information directly at
> server side. To get these information we have to use client side techniques
> such as ActiveX. At last, a user can still download a file twice if he uses
> another computer to access your web page.
>
> 3. Let a user send you his identity. In your case you've already let him
> send his phone number, etc. If you could force him to do so his identity
> can be used to check duplicate request. This is the weakest way because a
> user can cheat you by sending fake identity.
>
> In a word, there's no perfect way to restrict this. I think option 1 and 3
> are the easiest way. It can help to avoid duplicate download request to
> some extent. You can use the code in my previous code to check it. If you
> have any further questions, please don't hesitate to ask.
>
>
> Regards,
> Allen Chen
> Microsoft Online Support
>
>