I am running ubuntu linux 10.10.

Well, my program runs only on one instance, so what I need is to open my application's project file while the application is already running. By clicking this project file, the new program instance realize that there is already one running and it shows a message that the program is already open. What I want is to open the project file with the already running process. So, I want
1) If the program is already running and
2) there are arguments (a project file has been opened)
to open the project file with the already running process.

So, the new instance may send the URL of the project file to the already running process and the already running process open it. I have not idea how to do this. Maybe System-Wide Signal-Slot ?

Sorry if this is not a Newbie question. Fell free to move it to the Programming talk.