How do I find out what my external IP address is?

Question

My computers are sitting behind a router/firewall. How do I programmatically find out what my external IP address is. I can use http://www.whatsmyip.org/ for ad-hoc queries,

Answer 1

http://ipecho.net/plain appears to be a workable alternative, as whatismyip.com now requires membership for their automated link. They very kindly appear to be offering this service for free, so please don't abuse it.

Answer 2

If the router you are behind speak UPnP you could always use a UPnP library for whatever language you are developing in to query the router for its external ip.

Answer 3

Another way is if you have access to a cloud email (yahoo, google, hotmail), send yourself an email. Then view the headers and you should see your IP address in there.

I would look up the exact area but the headers may vary from each implmentation, Look for the received-by and follow that until you get to something that looks like sent-by

EDIT: This answers the how to find IP address, not the via PROGRAMMATIC approach

Answer 4

http://myexternalip.com provides this kind of information. To retrieve your IP you have plenty of options:

• http://myexternalip.com/ - browser + lot's of examples of how to use it
• http://myexternalip.com/raw - a pure text answer, only your ip, no other crap
• http://myexternalip.com/json - a resposnse ready for json-parsers, also supports jsonp
• HEAD http://myexternalip.com - send only a HEAD-request and get the answer

Answer 5

whatismyip.com or ipchicken.com are very easy to parse.

If you have a webhost or vps you can also determine it, without fear of it randomly going down leaving you stuck.

Answer 6

My WRT54G router tells me through its Local Router Access feature (the http(s) administration interface), and I imagine something similar could be done with many other devices. In this case, the entry page gives the octets of the IPv4 address in four lines containing this phrase:

class=num maxLength=3 size=3 value='i' name='wan_ipaddr_N' id='wan_ipaddr_N'

Where i is the octet value and N is the octet number. This bit of doggerel fetches and parses it for me, courtesy of cygwin:

#! /usr/bin/env perl
use strict;
use warnings 'all';

my( $account, $password ) = @ARGV;

open QUERY,
    "curl --sslv3 --user '$account:$password' https://Linksys/ --silent |"
    or die "Failed to connect to router";

my @ipaddr = ('x','x','x','x');

while( <QUERY> ) {
    $ipaddr[$2] = $1 if /value='(\d+)' name='wan_ipaddr_([0-3])/;
}
close QUERY;
print join('.', @ipaddr);

There is no guarantee that this will work with all versions of the router firmware.

If your router is set to use http for this interface, drop the --sslv3 curl option, and you can use dotted-decimal notation to address the router. To use https with the curl options above, I also did this:

1. Used a browser to fetch the router's self-signed certificate (saved as Linksys.crt).

2. Added it to my CA bundle:

   openssl x509 -in Linksys.crt -text >> /usr/ssl/certs/ca-bundle.crt
   

3. Added 'Linksys' to my hosts file (C:\Windows\System32\Drivers\etc\HOSTS on my Win8 box), as an alias for the router's address. If the dotted-decimal notation is given to curl instead of this alias, it rejects the connection on account of a certificate subject name mismatch.

Alternatively, you could just use the --insecure option to bypass certificate verification, which probably makes more sense in the circumstances.