Editing Message passing (section)

===Asynchronous message passing===
With asynchronous message passing the receiving object can be down or busy when the requesting object sends the message. Continuing the function call analogy, it is like a function call that returns immediately, without waiting for the called function to complete. Messages are sent to a queue where they are stored until the receiving process requests them. The receiving process processes its messages and sends results to a queue for pickup by the original process (or some designated next process).<ref>{{cite book|last=Orfali|first=Robert|title=The Essential Client/Server Survival Guide|year=1996|publisher=Wiley Computer Publishing|location=New York|isbn=0-471-15325-7|pages=[https://archive.org/details/essentialclients00orfa/page/95 95–133]|url=https://archive.org/details/essentialclients00orfa/page/95}}</ref>

Asynchronous messaging requires additional capabilities for storing and retransmitting data for systems that may not run concurrently, and are generally handled by an intermediary level of software (often called [[middleware]]); a common type being Message-oriented middleware (MOM).

The buffer required in [[asynchronous communication]] can cause problems when it is full. A decision has to be made whether to block the sender or whether to discard future messages. A blocked sender may lead to [[Deadlock (computer science)|deadlock]]. If messages are dropped, communication is no longer reliable.