C# RS232 serial communication

My objective: I have two different computers running two different C# programs. The two computers are connected by a long RS232 cable, each end connected on COM2. Each C# program has an identical static class: class TestClass { public static double var1; public static double var2; public static double var3; } I need code that can track changes in EITHER program, and update the static class in the other program with the changed values. For example, if var1 in program A becomes 5, then var1 in program B must also become 5. If var2 in program B becomes 3, then var1 in program A must also become 3. This should happen through RS232 serial communication, and be pretty reliable.