Getting external IP address

This topic is closed.

Steven D'Aprano
#1

Getting external IP address

Mar 5 '07, 09:05 AM

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

If I do this:

>>import socket
>>socket.gethos tbyname(socket. gethostname())

'127.0.0.1'

>>socket.gethos tbyname_ex(sock et.gethostname( ))

('localhost.loc aldomain', ['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.pytho n a few years ago:

Why no RE match of A AND B?

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.rea der.Sax import FromXmlStream
>>conn = HTTPConnection( 'xml.showmyip.c om')
>>conn.request( 'GET', '/')
>>doc = FromXmlStream(c onn.getresponse ())
>>print doc.getElements ByTagName('ip')[0].firstChild.dat a

Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/usr/lib/python2.4/UserList.py", line 28, in __getitem__
def __getitem__(sel f, 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
Tags: None
Duncan Booth
#2

Mar 5 '07, 09:15 AM

Re: Getting external IP address

Steven D'Aprano <steve@REMOVEME .cybersource.co m.auwrote:

>

>>>from httplib import HTTPConnection
>>>from xml.dom.ext.rea der.Sax import FromXmlStream
>>>conn = HTTPConnection( 'xml.showmyip.c om')
>>>conn.request ('GET', '/')
>>>doc = FromXmlStream(c onn.getresponse ())
>>>print doc.getElements ByTagName('ip')[0].firstChild.dat a

Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/usr/lib/python2.4/UserList.py", line 28, in __getitem__
def __getitem__(sel f, 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.c om')
>>conn.request( 'GET', '/')

>>resp = conn.getrespons e()
>>print resp

<httplib.HTTPRe sponse instance at 0x00C58350>

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

<html><head><ti tle>Object moved</title></head><body>

<h2>Object moved to <a href="http://www.showmyip.co m/xml/">here</a>.
</h2>

</body></html>

If you try connecting to 'www.showmyip.c om' and requesting '/xml/' it
should work.
Comment
Paul Rubin
#3

Mar 5 '07, 11:55 AM

Re: Getting external IP address

Duncan Booth <duncan.booth@i nvalid.invalidw rites:

If you try connecting to 'www.showmyip.c om' 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.
Comment
Duncan Booth
#4

Mar 5 '07, 12:35 PM

Re: Getting external IP address

Paul Rubin <http://phr.cx@NOSPAM.i nvalidwrote:

Duncan Booth <duncan.booth@i nvalid.invalidw rites:

>If you try connecting to 'www.showmyip.c om' 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?
Comment
Steven D'Aprano
#5

Mar 6 '07, 02:05 PM

Re: Getting external IP address

On Mon, 05 Mar 2007 09:02:44 +0000, Duncan Booth wrote:

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

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

>

>>>resp = conn.getrespons e()
>>>print resp

<httplib.HTTPRe sponse instance at 0x00C58350>

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

<html><head><ti tle>Object moved</title></head><body>
>
<h2>Object moved to <a href="http://www.showmyip.co m/xml/">here</a>.
</h2>
>
</body></html>

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

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

Thank you muchly! That seems to do the trick.

--
Steven.
Comment
Sion Arrowsmith
#6

Mar 6 '07, 05:25 PM

Re: Getting external IP address

Steven D'Aprano <steve@REMOVEME .cybersource.co m.auwrote:

>I have a PC behind a firewall, and I'm trying to programmaticall y
>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.

--
\S -- siona@chiark.gr eenend.org.uk -- http://www.chaos.org.uk/~sion/
___ | "Frankly I have no feelings towards penguins one way or the other"
\X/ | -- Arthur C. Clarke
her nu becomeþ se bera eadward ofdun hlæddre heafdes bæce bump bump bump
Comment
Cousin Stanley
#7

Mar 6 '07, 06:55 PM

Re: Getting external IP address

I have a PC behind a firewall, and I'm trying to programmaticall y
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.readlin es()
>>>
>>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
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Comment
Sergio Correia
#8

Mar 6 '07, 07:55 PM

Re: Getting external IP address

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 <cousinstanley@ hotmail.comwrot e:

>

I have a PC behind a firewall, and I'm trying to programmaticall y
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.readlin es()
>>
>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 =----
--

Mailman 3 Info | python-list@python.org - python.org

http://mail.python.org/mailman/listinfo/python-list

>
Comment
Steven D'Aprano
#9

Mar 6 '07, 10:05 PM

Re: Getting external IP address

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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