Semaphore.cs

// Server.exe:

        var s = new Semaphore(0, 1, Constants.SemaphoreName); //  public static readonly string SemaphoreName = @"Global\semName";

        var p = Process.Start(@"C:\Users\...\Debug\IpcChannelClient.exe");
        p.EnableRaisingEvents = true;
        p.Exited += P_Exited;
        //p.WaitForExit();

        Console.WriteLine("Entering waitone at: " + DateTime.Now.ToLocalTime());
        // Thread waits here until the sempahore is signaled (freed) from client process called above
        // we use semaphore here for demo purposes, but for waiting we would normally use p.WaitForExit()
        s.WaitOne(); // <-- thread waits here
        
        
// Client.exe
        
        // ..do work here...

        if (Semaphore.TryOpenExisting(Constants.SemaphoreName, out Semaphore s))
        {
            s.Release(); //Signal it here, so that server.exe can continue
        }