Monday 28 January 2013

Accessing your computers external IP address from your computer without using a browser

Access your computers external IP address from your desktop without using a browser

Following on from yesterdays blog post about what can happen if you get given a new IP address and don't realise it, you might want a quick way to check your external IP address from your computer without having to open an Internet browser.

There are many "What is my IP address" sites about that show you your IP address plus other request headers such as the user-agent but you might want a quick way of seeing your external IP without having to open a browser first.

If you are using a LINUX computer it's pretty easy to use CURL or WGET to write a small script to scrape an IP checker page and return the HTML contents.

For instance in a command prompt this will return you the IP address using CURL by scraping the contents of icanhazip.com.

This site is good because it outputs the computers IP address that's accessing the URL in plain text so it means you don't have to do any reformatting at all.

curl icanhazip.com

However if you are on a Windows computer there is no simple way of getting your external IP address (the IP address your computer is seen on the outside world) without either installing Windows versions of CURL or WGET first or writing a script to do it for you using Microsoft objects.

Of course it would be nice if you could just use ipconfig from the command prompt to show your external address as well as your internal network details but unfortunately you can't do that.

As you're connected to the Internet through your router your PC isn't directly connected to the Internet.

Therefore there is no easy way you can get the IP address your ISP has assigned to your computer without seeing it from another computer on the Internet.

Therefore you can either use one of the many IP checker tools like whatismyip.com or icanhazip.com to get the details. Or you can even just click this link to search for "what is my IP address" and get Google to show you your IP address above the results.

However if you do want to do it without a browser you can write a simple VBS script to do it for you and then you can access your external IP from your desktop with a simple double click of the mouse.

How to make a VBS Script to get your computers external IP address.
  1. Open notepad.
  2. Copy and paste the following VBS code into a new notepad window. 
  3. Save the file as "whatismyip.vbs" on to your desktop.
  4. To view your IP address just double click the file icon and a Windows message box will open and show you the IP address.
The script is very simple and all it does is scrape the plain text contents of the webpage at icanhazip.com and output it in a pop-up - simples!

Option Explicit
Dim objHTTP : Set objHTTP = WScript.CreateObject("MSXML2.ServerXmlHttp")
objHTTP.Open "GET", "http://icanhazip.com", False
objHTTP.Send
Wscript.Echo objHTTP.ResponseText
Set objHTTP  = Nothing

If you really want to use this from the command line you can do it by following these steps.
  1. Open a command prompt.
  2. Type "cscript " leaving a space afterwards (and without the quotes!).
  3. Drag the whatismyip.vbs file to the command prompt so that you have a space between cscript and the path of the file e.g C:\Documents and Settings\myname>cscript "C:\Documents and Settings\myname\Desktop\whatismyip.vbs"
  4. Hit Enter.
  5. The IP address will appear after some guff about the Windows Script Host Version.


The output should look something like this:

C:\Documents and Settings\
myname >cscript "C:\Documents and Settings\myname\Desktop\whatismyip.vbs"
Microsoft (R) Windows Script Host Version 5.7
Copyright (C) Microsoft Corporation. All rights reserved.
89.42.212.239

So there you go, a LINUX and WINDOWS way of accessing your external IP address from your desktop without having to open Chrome or FireFox.

Sunday 27 January 2013

Problem with SFTP after new router installation

Problem with SFTP / SSH after new router installation

This may seem like an obvious one but it can catch you out if you are not aware of the implications of having a new IP address assigned to your house's broadband. You may have moved your laptop to a new house or using a new wifi system to connect to the Internet.

More commonly you may have been given a new or upgraded router by your ISP provider.

Even if you are told the IP address has not changed by BT, Virgin, Sky, Verizon or whoever is giving you the new router you should do a check on any of the many IP checking pages out there on the web.

E.G this script shows you your current IP and ISP details.


Why is this important?

Well if you have your own server being hosted by a company e.g a cloud server somewhere and you have installed DENY HOSTS to block hacking attacks then you might find that you cannot SFTP (Secure FTP) into your server anymore or that using Putty and SSH to access your remote server suddenly stops working for no apparent reason. Obviously you want to access your server so the problem needs fixing.

Symptoms of an IP change causing problems include:
  • Your server reporting error messages such as "server unexpectedly closed the connection."
  • When you change the file transfer settings to simple FTP from SFTP you can access the server but then experience timeout errors or when the list directory command is run nothing happens.
  • Not being able to use Putty or another SSH tool to connect to your server.
  • Not having changed any settings on your computer but not being able to connect to your server anymore.

Solution to IP change:
  • Check and write down your new IP address.
  • Log into your server through WebMin or a web based system or from another computer that hasn't had an IP change.
  • Check your DENY HOSTS list to see if your IP address is listed and if so delete the record.
  • Add your new IP address in the ALLOW HOSTS list.
  • Re-start your server. 

If you don't know how to do this read the 3rd part of my Wordpress Survival Guide about security.