Message Passing

Mechanism for transferring information between processes :
Suitable for networked or distributed systems, using the IPC (Interprocess Communication mechanism). Simple message primitives :

• Send(P,Msg) : send a message of value Msg to process P. If P is busy, queue the message. The send operation does not block (suspend) the sending process. Asynchronous send
• Receive(P, Msg) : receive a message from process P, into variable Msg. Of no message has arrived from P, the receiving process is blocked.

  
Figure:

Server : Potentially multiple senders.
Do not know source of message (could have different receive primitives)
e.g. Src := Receive(Msg) (name of sending process returned in Src)