getmyip

function [ip,nslookup] = getmyip
% getmyip Retrieves the current external IP address and reverse DNS lookup value
%
% Syntax:
%    [ip,nslookup] = getmyip
%
% Description:
%    IP = GETMYIP retrieves the current machine's external IP address.
%    [IP,NSLOOKUP] also retrieves the reverse lookup (nslookup) value
%    for the external IP found.
%
%    GETMYIP uses whatismyip.com to find the IP and name-space.com for
%    the NSLOOKUP.
%
% Limitations:
%    GETMYIP uses external webpages so Internet connection is required (Duh!)
%    GETMYIP uses regexp, so it does not work on old Matlab versions
%
% Bugs and suggestions:
%    Please send to Yair Altman (altmany at gmail dot com)
%
% Change log:
%    2007-11-23: First version posted on <a href="http://www.mathworks.com/matlabcentral/fileexchange/loadAuthor.do?objectType=author&mfx=1&objectId=1096533#">MathWorks File Exchange</a>
%    2010-09-24: Modified external IP lookup URL based on Doug Schwarz's suggestion in http://www.mathworks.com/matlabcentral/newsreader/view_thread/292100

% Programmed by Yair M. Altman: altmany(at)gmail.com
% $Revision: 1.1 $  $Date: 2010/09/24 09:19:32 $

  try
      % Initialize
      ip = [];
      nslookup = [];

      % Try to read getmyip.org to find the external ip
      %if nargout
          % See the discussion in http://www.mathworks.com/matlabcentral/newsreader/view_thread/292100
          %ip = searchInUrl('http://getmyip.org', 'Your IP address is:</b>([^<]+)');
          ip = urlread('http://www.whatismyip.com/automation/n09230945.asp');
      %end

      % If external IP was found, try to find the reverse nslookup
      if ~isempty(ip) && nargout>1
          nslookup = searchInUrl(['http://name.space.xs2.net/cgi-bin/nslookup.pl?pageid=NSLOOKUP&submit=search&nsinput=' ip], 'Name:(.+)Address:');
      end

  % Error handling
  catch
      v = version;
      if v(1)<='6'
          err.message = lasterr;  % no lasterror function...
      else
          err = lasterror;
      end
      try
          err.message = regexprep(err.message,'Error using ==> [^\n]+\n','');
      catch
          try
              % Another approach, used in Matlab 6 (where regexprep is unavailable)
              startIdx = findstr(err.message,'Error using ==> ');
              stopIdx = findstr(err.message,char(10));
              for idx = length(startIdx) : -1 : 1
                  idx2 = min(find(stopIdx > startIdx(idx)));  %#ok ML6
                  err.message(startIdx(idx):stopIdx(idx2)) = [];
              end
          catch
              % never mind...
          end
      end
      if isempty(findstr(mfilename,err.message))
          % Indicate error origin, if not already stated within the error message
          err.message = [mfilename ': ' err.message];
      end
      if v(1)<='6'
          while err.message(end)==char(10)
              err.message(end) = [];  % strip excessive Matlab 6 newlines
          end
          error(err.message);
      else
          rethrow(err);
      end
  end

%% Read a webpage and search a substring within it
function data = searchInUrl(url, regexStr)

  % Ensure that hFig is a figure handle...
  str = urlread(url);
  [dummy1,dummy2,dummy3,dummy4,data] = regexp(str,regexStr);
  if ~isempty(data)
      data = strtrim(data{1});
      if iscell(data)
          data = data{1};
      end
  end