EcoStarter Solutions - How to turn on a computer remotely by SMS
How to turn on, shut down or reboot a computer remotely

A reliable, energy-efficient solution
without permanent Internet connection,
using an GSM-operated switch.

© 2009-2015, J.Hulaas,

Page 1 | 2 | 3

You have a PC offering useful services through the Net, or a file server giving you access to its documents remotely, but:

  • You do not want to leave it turned on, consuming electricity all the time, just in case you should need to access it?
  • You do not have a permanent Internet connection, or, for security reasons, you'd rather not keep the computer accessible all the time on the Internet ?
  • You do not want, or do not succeed in configuring your system for WOL (Wake-On-LAN) through Internet?
  • You need an uncompromising way of rebooting the computer from a remote location (which a software or modem-based solution does not enable) ?

Issues with Wake-on-LAN (WOL)
WOL is a special message that can be sent through a network to a given computer to make it wake up. This may seem as a panacea, but it entails in fact a number of significant issues:

  • Consumption:
      When running, a computer typically consumes between 50 and 500 watts, depending on its configuration. When switched off, but still waiting for a WOL message on its network interface, the computer will neccessarily still consume a few watts, to which the network equipment (modem, router, switch) must be added in order to be able to receive the WOL message coming in from the Internet.
  • Security:
      The WOL mechanism was initially created for local networks; this means that the protection level has to be reduced (at the firewall or router level) in order to allow a WOL message to enter the local network from the Internet.
  • Missing address:
      In order to send a WOL wake-up message to a given computer, you have to know its Internet address. Unfortunately, a computer that is turned off will precisely often have no address! Moreover, it will also need a permanent Internet connection to be able to receive the WOL message at any time.
  • Reliability:
      The computer does not acknowledge receipt of WOL messages, and you won't know if it was received at all before the computer has finished starting up and somehow signalled its presence on the network. A further important issue is that if a computer crashes, it is unfortunately impossible to restart it without physical access to its power supply or to its start or restart button.

To summarize, using WOL to wake up a remote computer will admittedly work in a number of cases, and it is free to use, but it has downsides and requires non-trivial configuration steps (to convince yourself, just look at the millions of pages related to that topic on the Web) !

Our Solution: an SMS-operated switch to start the computer
To address these issues, we propose to do without WOL and instead to completely switch off the computer and its network equipment(1). Then, you can turn the computer on remotely using a simple SMS (short text message) or smartphone app!

(1)except certain ADSL/cable modems that are supposed to always stay on.

Ready-made solution
by controlling the mains power supply
Fine-tuned solution
by controlling internal contacts
With GSM Mini:

Supported functions:

Turn computer On/Off
(by admitting/cutting the mains power)

Hardware reset/cold boot
(by briefly cutting the power supply)

Turn On/Off for a given duration

With GSM 12A+:

Supported functions:

Turn computer On/Off
Enter/exit sleep mode
(operation of "start" button)

Hardware reset
(operation of "reset" button)

Temperature surveillance and alarm by SMS
(inside computer case or in computer room)

Other possible alarms by SMS:

  • Displacement/opening of computer case.
  • Power outage (requires an optional backup battery for dispatching the alarm).
  • Malfunction (hardware issues).

The computer can be configured for automatically starting up as soon as the mains power is restored (this is usually a setting in the operating system or the BIOS).

How-to Guide »»»

The computer's internal start-up contacts are accessible (anywhere along the wires connecting internally the start button to the motherboard).

How-to Guide »»»

How do I access the computer once it has been started ?
If the computer has a fixed IP address on the Internet, no problem, you'll use that for connecting to your computer. But if the computer has a dynamic IP address, it will have to communicate it to you in order to enable you to connect. It could e.g. send you an e-mail with this information. An easier way is to use, which distributes a dedicated and free software tool for all major platforms: once installed on your computer, it will make your computer known by a domain name chosen by you, e.g.

How do I turn off my computer remotely ?
In order to preserve the integrity of the computer's data and software, it is important to give a shutdown command to it before the power gets cut off by SMS. The exact procedure will depend on the software solution you chose to access the computer remotely. In most cases, it suffices to open a command-line ("terminal") window on the remote computer in order to launch the shutdown. This list of shutdown commands is usable on remote Windows computers, whereas on Mac OS X and Unix/Linux, the "shutdown" command is almost universal. This method is to be used with the above "Ready-made solution" (SMS-operated 230V socket).

However, you will get more flexibility and additional functionality by setting GSM 12A+ to exploit the system startup contacts of your computer, as described in the right-side column above: you'll be able to put the computer in sleep (standby) mode, or even better, in hibernation mode. With hibernation, all your current data in working memory (RAM) is safely saved to permanent storage (the hard disk) before the power is cut off; this is even better than sleep mode since the computer then consumes no electricity at all. Furthermore, the computer will start faster than if it were shut down in the traditional way. The various functions of the computers power button are normally set in the operating system:

  • On Windows XP: "Control Panel" -> "Power Options" -> "Hibernate" tab -> check "Enable hibernation", and click "Apply" -> "Advanced" tab -> In the "Power buttons" section, you select the desired behaviour in the drop-down menu.
With this configuration, you can send an SMS to your GSM 12A+ to make it establish a brief contact at the level of the computer's power button - exactly as if you were there personally and pressed the button with your finger - and thus make your computer get in and out of hibernation remotely!

Page 1 | 2 | 3

Your comments are welcome!