Getting cross-platform IP address

[Alex Rice]

On Wednesday, August 27, 2003, at 04:15  PM, Dar Scott wrote:
> On Wednesday, August 27, 2003, at 03:09 PM, Scott Slaugh wrote:
>> The address function should work without a connection to the 
>> internet.  However, the hostNameToAddress() function does a DNS 
>> lookup, and as such requires an internet connection to work properly. 
>>  (See the entry in the Transcript Dictionary for hostNameToAddress 
>> for more information about this.)

I speculate it won't *necessarily* do a DNS lookup. It depends how the 
name service resolver is configured. On Mac OS X the resolver will use 
Appletalk and Netinfo first, then DNS. On Unix it can use the 
/etc/hosts file, then DNS, depending on the ordering in the file 
/etc/resolv.conf. YP/NIS and maybe others could be involved too.

On my OS X , "the address" returns "localhost:/...". localhost is 
resolved as the loopback address, 127.0.0.1, which can't be decided by 
a DNS server.

> What if I don't even know my host name or I have none or my DNS 
> doesn't know it?
>
> 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.

--
BTW is this a  documentation error in "the address"?

" Cross-platform note:  On Unix systems, the computer's name is its 
domain name. On Mac OS systems, the name is the one set in the File 
Sharing control panel."

re: the Unix computer's name. AFAIK it depends on the contents of 
/etc/hosts which usually isn't going to be domain name, it's going to 
be localhost plus one or more aliases. On Mac OS X, the statement could 
be true, if "the address" returned the rendezvous domain for the 
computer, e.g. darkstar.local (a local domain name for my computer with 
the name darkstar). But it doesn't return the rendevous name.




Alex Rice, Software Developer
Architectural Research Consultants, Inc.
http://ARCplanning.com