How can I get the client IP address correctly?

Question

Hi,
I am having a problem with getting the client ip address correctly using jsp. I am currently using the method request.getRemoteAddr() (JSP)to get the remote client IP. This method works fine with intranet addresses.
However, when I am using a dial-up connection through a ISP (internet service provider), it could not detect the actual IP that is assigned to my client PC, but instead got another IP address.
Could anyone advise me on that? And could anyone advise me on how to obtain the correct client ip address correctly using any of the java technologies?
Thanks,
Damien

Answer 1

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I don't believe so. You can't establish aconnection
over the internet using a private IP. As far as I
know most, if not all routers, block them so itwon't
even move over the backbone.Well with port-mapping it is definately possible to
allow an external ip to "connect" to an internal ip, i
have done this very thing myself...Not the same.
You are addressing the external server with a public IP address. That is then translated into the internal connection.
That is not the same as using a private IP on the internet.
As I said, the backbone will not let a private IP through.
>
>
Yes, but my point is that at any given time, in the
world, many boxes might have one address. Even ifit
is a private IP is it still that IP for aparticular
box. So if you use java to get its IP that is theIP
that it gets. And that IP is useless for anything
unless that IP is meaningful for the othercomputer.
But all ips must be unique in a designated "internet"
be it an "intranet" or whatever, there cannot be a
situation where two identical ips in the same
"internet", such that an ip that is achieved from a
page-hit is valid and meangingful in order to send the
data it is requesting back to it, or find out more
about that computer, or log and report it if it is
doing something illegal; i don't think its that
meangingless is it?Yes it is. You can't use an IP to uniquely identify a box, and that is the sole criteria, when there might be two boxes with the same IP.
When you use java on a client box to get the IP of the box, it doesn't necessarily return an IP that it meaningful to the anyone outside the lan on which the box lives.
Because of this internet systems must do one of the following:
-Do not use the IP as an identifier.
-Require that the client has a public IP. This is often static. At least some security systems use this to validate users.