Thursday, December 26, 2013

Remote access; what's the IP address?!

If, like me, you're tech support for family and friends you often have a need to take remote control of a relative's machine over the internet. There are lots of ways; the easiest being the paid-for services like GoToMyPC, TeamViewer etc which all offer NAT traversal with very  little effort required at each end to make them work. You just give the person you're helping a ticket number and a URL and before you know it (and normally by Java or some other active web content) you're controlling their screen. They have VOIP as well and it's very slick. However, I don't do enough remote support to justify keeping an account going at ten dollars a month and I quite like VNC/RDP etc.
The problem with those protocols is that you need to know the public IP address of the recipient's router and this changes by the vagaries of their ISP and DHCP etc.
So, here's my method for always knowing the public facing IP address of your Mum's computer without having to run anything clever at her end or anything as elaborate as a VPN.
  1. Make sure you've made a port-forwarding rule on their router so that when you hit them on port 5900 (for VNC) or port 3389 for Windows remote desktop it gets forwarded through to the target machine; you'll probably have to have given that computer either a fixed IP address or have set the router to always assign it the same DHCP'ed IP address.
  2. Have that machine genarate a file at boot-time that contains the correct external IP address along with any other salient data that you might find useful.

The first part requires you to know their router - it's not hard, you'll just need to look around in its web interface. Here's how I do the second part;

I stick these four files in a convenient directory - typically c:\tools\ but anywhere will do. 
wget.exe is an open-source Windows implementation of the common Linux/OS-X tool that fetches text fields from a web server.
GetIP.bat is a Windows batch file that sticks the output of wget into a text file and appends some extra stuff (IPConfig, date and time) and then initiates an FTP session with any web space you may have under your control. Finally index.html is the generated text file (makes the final URL easy to remember).

wget -O - -q > index.html

ipconfig >> index.html
time /t >> index.html
date /t >> index.html

ftp -s:ftp.txt


cd htdocs
cd bob

send index.html

Stick a shortcut to GetIP.bat in the startup folder (and for extra finesse have it run minimised so nobody sees it) and every time the machine boots you get uploaded to the webserver a very useful status page;

So long as you have a VNC or RDP server running at the remote end you're now only a moment away from being a tech support super-hero!

1 comment:

Tim Taylor said...

Excellent ideas and explanation - this method well worth using.