Getting external IP address

[Steven D'Aprano]

I have a PC behind a firewall, and I'm trying to programmatically
determine the IP address visible from outside the firewall.

If I do this:

>>> import socket
>>> socket.gethostbyname(socket.gethostname())
'127.0.0.1'
>>> socket.gethostbyname_ex(socket.gethostname())
('localhost.localdomain', ['localhost'], ['127.0.0.1'])

I get my internal IP address, which is not what I want.

Other tricks, like parsing the output of os.system('/sbin/ifconfig eth0')
also give me my internal IP address.

I found this post on comp.lang.python a few years ago:

http://mail.python.org/pipermail/python-list/2003-March/192495.html

which seems like it _should_ do what I want, but it doesn't: I get an
exception.

>>> from httplib import HTTPConnection
>>> from xml.dom.ext.reader.Sax import FromXmlStream
>>> conn = HTTPConnection('xml.showmyip.com')
>>> conn.request('GET', '/')
>>> doc = FromXmlStream(conn.getresponse())
>>> print doc.getElementsByTagName('ip')[0].firstChild.data
Traceback (most recent call last):
  File "", line 1, in ?
  File "/usr/lib/python2.4/UserList.py", line 28, in __getitem__
def __getitem__(self, i): return self.data[i]
IndexError: list index out of range
>>> conn.close()

I don't know how to fix it so that it works.

Can anyone help me fix that code snippet, or suggest another (better) way
to get the externally visible IP address?


-- 
Steven D'Aprano 

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Re: Getting external IP address

[Duncan Booth]

Steven D'Aprano <[EMAIL PROTECTED]> wrote:

> 
 from httplib import HTTPConnection
 from xml.dom.ext.reader.Sax import FromXmlStream
 conn = HTTPConnection('xml.showmyip.com')
 conn.request('GET', '/')
 doc = FromXmlStream(conn.getresponse())
 print doc.getElementsByTagName('ip')[0].firstChild.data
> Traceback (most recent call last):
>   File "", line 1, in ?
>   File "/usr/lib/python2.4/UserList.py", line 28, in __getitem__
> def __getitem__(self, i): return self.data[i]
> IndexError: list index out of range
 conn.close()
> 
> I don't know how to fix it so that it works.
> 
> Can anyone help me fix that code snippet, or suggest another (better) 
way
> to get the externally visible IP address?

Try running it interactively and looking at the data you receive:

>>> conn = HTTPConnection('xml.showmyip.com')
>>> conn.request('GET', '/')

>>> resp = conn.getresponse()
>>> print resp

>>> data = resp.read()
>>> print data
Object moved

Object moved to http://www.showmyip.com/xml/";>here.





If you try connecting to 'www.showmyip.com' and requesting '/xml/' it 
should work.
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Re: Getting external IP address

[Paul Rubin]

Duncan Booth <[EMAIL PROTECTED]> writes:
> If you try connecting to 'www.showmyip.com' and requesting '/xml/' it 
> should work.

If the firewall is really obnoxious, it can bounce consecutive queries
around between multiple originating IP addresses.  That is uncommon
but it's been done from time to time.
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Re: Getting external IP address

[Duncan Booth]

Paul Rubin  wrote:

> Duncan Booth <[EMAIL PROTECTED]> writes:
>> If you try connecting to 'www.showmyip.com' and requesting '/xml/' it 
>> should work.
> 
> If the firewall is really obnoxious, it can bounce consecutive queries
> around between multiple originating IP addresses.  That is uncommon
> but it's been done from time to time.

Yes, each connection through the firewall needs to have a unique 
originating ip and port number. If there are too many machines inside the 
firewall then you may need to allocate multiple ip addresses on the 
outside. I would hope that in general a single internal IP should map to 
one external IP at a time (otherwise you would have problems with ip based 
session persistence connecting to load balanced systems), but you might 
expect to bounce round different IPs after periods of inactivity.

Also you could have multiple levels of NAT in which case the question 
becomes whether Steven wants the IP as seen from outside the immediate 
firewall or outside the final one. Maybe he should be using IPv6 to avoid 
all this?
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Re: Getting external IP address

[Steven D'Aprano]

On Mon, 05 Mar 2007 09:02:44 +, Duncan Booth wrote:

> Try running it interactively and looking at the data you receive:
> 
 conn = HTTPConnection('xml.showmyip.com')
 conn.request('GET', '/')
> 
 resp = conn.getresponse()
 print resp
> 
 data = resp.read()
 print data
> Object moved
> 
> Object moved to http://www.showmyip.com/xml/";>here.
> 
> 
> 

Ah! That's the clue I needed -- thanks.

> If you try connecting to 'www.showmyip.com' and requesting '/xml/' it 
> should work.

Thank you muchly! That seems to do the trick.


-- 
Steven.

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Re: Getting external IP address

[Sion Arrowsmith]

Steven D'Aprano  <[EMAIL PROTECTED]> wrote:
>I have a PC behind a firewall, and I'm trying to programmatically
>determine the IP address visible from outside the firewall.
>  [ ... ]
>Can anyone help me fix that code snippet, or suggest another (better) way
>to get the externally visible IP address?

Depending on your circumstances, it may be possible to just ask the
firewall. You'll probably need some kind of administrator login, and
may well have to parse HTML if it's only got a web interface, but it
does mean that you don't have to connect to anything in the outside
world.

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Re: Getting external IP address

[Cousin Stanley]

> I have a PC behind a firewall, and I'm trying to programmatically
> determine the IP address visible from outside the firewall.
> 

Steven  

  Following is another alternative that might at least
  be worth consideration 

  I use the  lynx  command shown as a command-line alias
  under Debian linux 
 
>>>
>>> import os
>>>
>>> pipe_in = os.popen( 'lynx --dump http://checkip.dyndns.org' )
>>>
>>> ip_addr = pipe_in.readlines()
>>>
>>> for this in ip_addr :
... print this
...


   Current IP Address: 65.39.92.38


-- 
Stanley C. Kitching
Human Being
Phoenix, Arizona


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Re: Getting external IP address

[Sergio Correia]

The above suggestions seem nice, but I find this one easier:

import urllib2
ext_ip = urllib2.urlopen('http://whatismyip.org/').read()
print ext_ip

The nice thing about the above code is that http://whatismyip.org/
only contains exactly what you want (the ip, nothing more, nothing
less), so no parsing is necessary

Best,
Sergio

On 3/6/07, Cousin Stanley <[EMAIL PROTECTED]> wrote:
>
> > I have a PC behind a firewall, and I'm trying to programmatically
> > determine the IP address visible from outside the firewall.
> > 
>
> Steven 
>
>   Following is another alternative that might at least
>   be worth consideration 
>
>   I use the  lynx  command shown as a command-line alias
>   under Debian linux 
>
> >>>
> >>> import os
> >>>
> >>> pipe_in = os.popen( 'lynx --dump http://checkip.dyndns.org' )
> >>>
> >>> ip_addr = pipe_in.readlines()
> >>>
> >>> for this in ip_addr :
> ... print this
> ...
>
>
>Current IP Address: 65.39.92.38
>
>
> --
> Stanley C. Kitching
> Human Being
> Phoenix, Arizona
>
>
> == Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet 
> News==
> http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ 
> Newsgroups
> = East and West-Coast Server Farms - Total Privacy via Encryption =
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: Getting external IP address

[Steven D'Aprano]

On Tue, 06 Mar 2007 14:40:37 -0500, Sergio Correia wrote:

> The above suggestions seem nice, but I find this one easier:
[snip]


Thanks to everybody who replied, that's great.


-- 
Steven.

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