How to test the code of a protocol implementaion?

Are there any useful method to test code of a protocol implementation ?

I'm trying implementing the Time Warp protocol which is used in parallel discrete event simulation.It's kind of complicated to me.I find it's difficult to design test cases to test the code. I know that many complicated protocols in parallel and distributed computing area have been developed and used in industry.They must be tested thoroughly.I need experience on testing protocol.