[twsocket] Need Advice / Help on how to find the correct IP's

Wilfried Mestdagh wilfried_sonal@compuserve.com
Tue, 13 Jun 2000 10:44:48 +0200


Hi Ralf,

You are never 100 procent sure.

- A LAN can have a public address (it should not).

- If the internet connection is tru a router witch does NAT then you have
internet connection to the LAN card with a private ip address.

rgds, Wilfried

> -----Original Message-----
> From: twsocket-admin@elists.org [mailto:twsocket-admin@elists.org]On
> Behalf Of Ralf Buml
> Sent: dinsdag 13 juni 2000 5:36
> To: twsocket@elists.org
> Subject: RE: [twsocket] Need Advice / Help on how to find the correct
> IP's
>
>
>
> Hi Wilfried!
>
> >Please include the original question in future. As I remember
> you wanted to
> >know if you had a connection on witch interface it was or witch
> one was the
> >internet one.
> I'm sorry, i didn't know that :( Shouldn't happen again!
>
> My question was: "How can i determine which of the IP-Adresses is assigned
> to the internet and which one is the IP of the network-card"
> I want to know that before the connection is made.
> Just like the Windows-Tool NETIPCFG
>
> The problem is: My program gets the IPs already but sometimes
> does the mistake to sitch these adresses so they are in the wrong place.
>
> Example:
> Private Network-IP: 192.168.0.1
> Internet-IP:  62.244.34.132
>
> So if the user has 1 Network card my program tells him:
> Private Network-IP: 192.168.0.1
> Internet-IP: None
>
> if the user has 1 Network card and is has an Internet-IP at the
> same time my program tells him:
> Private Network-IP: 192.168.0.1
> Internet-IP: 62.244.34.132
>
> And now the problem again:
> if the user has only an Internet-IP and no Network card installed
> my program tells him:
> Private Network-IP: 62.244.34.132
> Internet-IP: None
>
> And thats the problem. I want to be 100% sure which one is
> assigned to which interface.
>
> Hope you have an idea...
>
> Greets
> 	Ralf
>
> >Wel if you can connect with addr '0.0.0.0' you have the ip of the server.
> >You can call LocalIpList to get list of all interface cards.
> Next step is to
> >set LocalAddr property to the first one and try to connect
> again. If it dont
> >work, then it's the wrong one, you can try the next, etc, and if
> connect is
> >ok then you have the interface witch is connected to internet.
> >
> >If I'm completely wrong here pleas ask the original question again.
> >
> >rgds, Wilfried
> >
> >> -----Original Message-----
> >> From: twsocket-admin@elists.org [mailto:twsocket-admin@elists.org]On
> >> Behalf Of Ralf Buml
> >> Sent: maandag 12 juni 2000 19:43
> >> To: twsocket@elists.org
> >> Subject: RE: [twsocket] Need Advice / Help on how to find the correct
> >> IP's
> >>
> >>
> >>
> >> Hi Wilfried!
> >>
> >> Thanx for your answer! :)
> >>
> >> It's ok... I knew the thing with the IP-Adresses already.
> >> But as your last paragraph says some users don't know
> >> which IP-Adresses are valid. (I was such a user some years
> >> ago, wondering why my Network never worked on TCP/IP :)))
> >>
> >> Is there no other way than checking these adresses?
> >> This way is much too unsecure for my needs and will be the
> >> last escape if any other way is possible...
> >>
> >> Greets
> >> Ralf
> >>
> >> >Normally (if lan ip properly configured), the lan ip address
> should be a
> >> >private netwerk, and the internet ip address is a public one.
> >> Difference is
> >> >a private network is normally not routed. Private are:
> >> >
> >> >class A (for very large networks):
> >> >10.0.0.0 / 8
> >> >
> >> >class B (for large networks):
> >> >172.16.0.0 / 12
> >> >
> >> >class C (small networks):
> >> >192.168.0.0 / 16
> >> >
> >> >Note if someone does not untherstand: the /nn is the number of bits
> >> >belonging to the network. eg: the class B machines: is from
> 172.16.0.1 to
> >> >172.31.255.254
> >> >
> >> >However, I have seen many LAN's with public addresses also
> because many
> >> >people (including the network administrators) does not know it.