Multiple Network Instances?

Hey everyone,
I've got a design question for you guys. I have an program that could potentially be run from multiple workstations on a network. When this program starts, it needs to know if there are any other instances of itself already running somewhere on the network.
The only way I could think of doing this is creating a temporary file in a network location where all workstations can see when an instance of this program is started. Then when an additional instance of the program starts, it can check for the presence of this file. When the program is closed, the file is deleted.
Would there be a better way to accomplish this?
Thanks,
-Chris

I've been researching multicasting a bit since I first posted. Since I've never dealt with this yet, it seems a bit strange to me. As far as I can understand you need both a client and server in order to send and receive? I don't quite understand how one program can send and receive packets at the same time.
- Chris

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