Deskolo project: open source Green IT solution

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In a previous article we described how we model power consumption in the Deskolo project. In this article we’ll see how we use the standard technology Wake-On-Lan to save on the energy bill.

Green IT solution

One way to implement a green IT solution is to control the time the machines are up on your network. The less time the machines are up the better. To do this in the Deskolo project, there are 3 components:

  1. a web application that can navigate into the power consumption data from supervised clients.
  2. the supervision server that takes care of managing the supervised clients.
  3. supervised clients that take orders from the server.

Clients are waiting for orders from the server to avoid saturating the server. The 2 most important orders are the following ones:

  • give power consumption on a period of time.
  • give the activity periods where the machine will be up for each day of the week.

The full protocol is available in this document.


The clients are responsible for switching off the system when there is no more user activity outside the predefined activity periods. By default, in the sample implementation, the client code is suspending to ram the system to have a faster wake up.

The server is responsible to wake up the suspended or switched off clients. To do this, the server uses the wake-on-lan technology in 3 ways:

  1. if the server detects that the client to wake up is on the same network, it sends a broadcast wake-on-lan packet.
  2. if the server finds a connected client on the same network as the client to wake up, it sends a request to the connected clients to send a broadcast on its local network.
  3. if the server can’t find a relay, it assumes that the client is behind a NAT and that the firewall acts as a proxy wake-on-lan. This is the case for example for ADSL boxes from the French operator free.


If you want to experiment with Deskolo you can download the server side and the client side source codes that are available today in version 0.1 from our download area. Both parts should run under any Linux.

The client part deskolo-client-0.1 is a sample implementation of the protocol. This is realized as a system daemon with a configuration file to declare the activity periods, the address of the Deskolo server and the command to suspend or switch off the system.

The Deskolo project members will release graphical Deskolo clients for Linux and Windows soon. Stay tuned!

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