the postman class documentation

postman gets initialized with a binstream. it keeps a pointer to it.
you must make sure the binstream objects lives longer than the postman!

  if correct, but unregistered messagekinds arrive, the postman emits corruptreceived().
  postman does also emit corruptreceived() if a messagekind or a message is corrupt.
  postman emits corruptreceived() only once.
  from then on the receiving part of the communication is dead.
  it is not possible to recover, because the
  postman does not know the size of unknown messages and thus looses
  synchronization on the binstream

  the returned signal??? stuff when calling receiver_open or with sender_open
  are only valid until close is called!!!

  it is your duty to make sure the binstream object the postman uses exists
  for the whole lifetime of the postman.
  so don't delete the stream and the postman still has a pointer to it.
  yes i could have used smartpointers for this. but i didn't do so.
  now you are free of my smartpointers if you use postman only.      

the order of messages is preserved.
i.e. if sending a,b,c   you will receive a,b,c    in the same order.