Getting IP Address of Machine that is Currently Running the Stack

[Dar Scott]

On Oct 25, 2006, at 7:09 AM, Dave wrote:

> How can I get the IP address of the machine that a stack is running  
> on?

Open a datagram socket to a legal IP address.  That does not have to  
be assigned.  Then get the hostAddress of that socket.  Then close  
it.  The hostAddress will be what you want.

If the machine has more than one IP address, the address will be the  
one that would be used in trying to make the connection.  For  
example, on a firewall, the machine might have both a public IP  
address for one adaptor and a private IP address for the LAN on  
another adaptor.  Also, a single Ethernet LAN might have more than  
one IP address assigned to an adaptor on a machine (I use this for  
addressing both my network and instruments that come with a fixed IP  
address).  And then there are dialups and VPNs and...

The cool part about the datagram method is that it is not intrusive.   
It does not try to do anything on the net.

If you want the IP address of the default adaptor, try  
"255.255.255.255".  This does not always work; I forgot the constraints.

This method would not work at one time on OS X, but that was fixed.

Dar

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Dar Scott
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Computer programming
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