Make sure that test cases does not fail due to timing circumstances,
use selective receive even if it means we can not use test library functions
in some cases. TCP does not have delivery guarantee to application layer,
so sometimes a error message {error, Msg} or {error, closed} can be acceptable.

New design : ssl - Main
    	     tls - Reflect tls specific semantics
	     dtls - Reflect dtls specific semantics