Getting cross-platform IP address

Dar Scott dsc at swcp.com
Wed Aug 27 18:38:01 EDT 2003


On Wednesday, August 27, 2003, at 04:56 PM, Alex Rice wrote:

>> I think the goal is to get the primary IP address of the computer not 
>> of a connection.  I may be confused there, too.
>
> But is there such thing as really a primary IP address? There is a 
> default gateway for each network interface. There can be priorities 
> assigned to different routes. However, the particular interface to use 
> isn't decided until the OS needs to send some particular network 
> packets and the OS goes- ok little packet: where's that network- 
> where's that default gateway- what's the route's priority hm.. hm... 
> you go out this interface.
>
> Maybe this is why hostAddress requires a socket to be opened- it is 
> only capable of answering the endpoint IPs of that one socket.

That is a very good point.

I have some computers with several ethernet adaptors, some over-modem 
adaptors, and several VPN adaptors.  And then there is 127.0.0.1.  I 
have some computers which connect to multiple subnets on the same 
ethernet adaptor.  Which is primary?

I think Windows thinks one is primary, but I'm not sure.

This is why I like the idea of an adaptors() or ipAddresses() function. 
  Or the ability of hostAddress to take an unopened connection.

Now if only hostAddress will take a UDP opened socket...  That is 
really in some sense an unopened connection.

Dar Scott






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