Finding IP address of localhost via socket API (or other API)

[Steven D'Aprano]

Sorry for replying to the replier (Timothy) instead of the OP (David), 
but the original post seems to have been eaten by my ISP.

On Tue, 05 Aug 2008 15:48:26 -0700, Timothy Grant wrote:

> On Tue, Aug 5, 2008 at 2:50 PM, David York <davideyork at gmail.com> wrote:
>> Does anybody know how to find the real IP address (e.g.: address
>> visible to internet) of a machine via Python?  In other words I have a
>> machine with an IP address something like 192.168.1.5, an address given
>> to me by a router. The router's address (and thus my machine's address)
>> to the outside world is something realistic, 123.156.123.156 or
>> whatever.  How do I get that number?  I've tried
>> socket.getaddrinfo('localhost', None) but all I get is 127.0.0.1 as
>> expected.
>>
>> How do I find out my machine's IP address as visible to the outside
>> world? Thanks a lot.
>>
>>    David
> 
> I'm not sure what you are trying to accomplish. The machine I'm typing
> this on has a 192.168.x.x number. The router that gave it to me also has
> a 192.168.x.x number. However, I know that that is not the IP that the
> world sees when my packets finally leave the building.

That's the IP address the OP probably wants. At least, when I've asked 
this exact same question, that's what I meant.

The only way I know of is to query an external server that will tell you. 
There's a few of them out there. Here's a few:

http://checkip.dyndns.org/
http://www.showmyip.com
http://www.showmyip.com/simple/
http://whatismyip.org/

The basic algorithm is to connect to one of those sites and fetch the 
data it returns, then parse it appropriately. Some of them return a 
simple IP address, some a complicated bunch of text, some a nicely 
formatted XML document. Some of them only allow you to query the server a 
limited number of times. I don't remember which is which.

To get you started, here's an untested piece of code:

import urllib2
import re
data = urllib2.urlopen(site).read()
matcher = re.compile(r"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}")
ip_address = matcher.search(data).group()



-- 
Steven