IP Recovery With C++

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

Hello,

I have a question concerning a program that I am developing.

The program itself needs the IP address of the local computer in order to
work properly. The only problem is that I don't know a way to recover the
machines ip address. And another problem arises if I want to work with the IP
address: Routers. How will I be able to retrieve the good ip address (for
instance my network connection status states that my ip is ***.***.***.** and
if I go to www.whatismyip.com to retrieve my ip it states something
completely different (the latter is the ip of the network and the first one
was the ip that my engine got from my router)

How to solve this problem?

Thanks in advance,

Dexter
 
Dexter Drupsteen said:
The program itself needs the IP address of the local computer in order to
work properly. The only problem is that I don't know a way to recover the
machines ip address.
Click to expand...

The local machine may have several IP addresses, one for each network
interface. For example, 127.0.0.1 is the loopback interface. Then, for
each network card in the system attached to an IP network, there will be
a different IP address.

Here's a program which enumerates the IP addresses for the local
machine:

http://www.devcity.net/Articles/78/1/getipaddrs.aspx
And another problem arises if I want to work with the IP
address: Routers. How will I be able to retrieve the good ip address (for
instance my network connection status states that my ip is ***.***.***.** and
if I go to www.whatismyip.com to retrieve my ip it states something
completely different (the latter is the ip of the network and the first one
was the ip that my engine got from my router)
Click to expand...

That is because of NAT, network address translation. Basically, the
router multiplexes all the machines inside the LAN across 1 or more
external IP addresses. To get this information, you either need to talk
to the network administrator, interface in a vendor-specific way with
the router, or contact an external machine (such as www.whatismyip.com)
to discover the external IP address.

Note that NAT routers can multiplex multiple connections from the same
machine across multiple IP addresses (and possibly multiple ISP
connections, for speed or redundancy), so for independent requests the
IP address may be different.

-- Barry
 
Back
Top