How to communicate with .net processes when there are multiple instances of them

I have multiple instances of the same Windows Forms .net 3.5 SP1 C# application running on the same machine.

Now I'd like to be able to communicate with them from .net, one instance at a time. What's the most simplest way to do this?

I read a bit about WCF, but I have only found examples working with one server and one client. But in my case all running instances would be a server and I need to discuss with just one of them.

I imagine something like this:

Process[] procs = Process.GetProcessesByName("ProcessName");开发者_StackOverflow
foreach (Process p in procs)
{
  // Communicate with process here
}

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You'll need some kind of subscribe/callback mechanism. Don't loop through the projects, but have each application subscribe to a wcf service method instead.

Example: http://idunno.org/archive/2008/05/29/wcf-callbacks-a-beginners-guide.aspx

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The simple thing is database :) , btw WCF support peer to peer communication with NetPeerTcpBinding