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TCP/IP Addresses and Visual Basic

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Last Modified: 2013-11-25
Does anyone know how to obtain the default IP address being used by a workstation (without using an OCX). I've been using the Win 32 GetHostByName function, but this only returns the first bound IP address on the workstation regardless if it is being used or not. If someone has a network card installed and is has dial up networking, I need to know which one is currently in use (assumption is that both of them will not be used at the same time).

Any help would be appreciated.

Thanks,
Dave Schwietz
www.selectinc.com
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Commented:
The normal way to get the IP address being used is to create a socket without an IP address assigned to it, then open a connection to wherever you want to reach, and then check what address has been assigned to the socket.

If a workstation has more than one IP address, you can never say that a certain IP address is not in use, you can only say that it wouldn't be used to reach a certain target. The most default IP address must be the one which is on the same subnet as the default gateway, because if you haven't defined any special routing rules, most packets will go that way.

However, when workstations are connected to an Intranet via network adapters, and Internet via modem, there can at the same time be sessions to an Intranet WWW server using the LAN adapters IP address and sessions to external Internet servers using a single program such as Internet Explorer. Which IP address is the one in use then?


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