Explain Direct or Indirect Communication in Inter-process communication.
Several types of message passing system in Direct or Indirect Communication are given below:
With direct communication, each process which wants to communicate should explicitly name the recipient or sender of the communication. In such scheme, the send and receive primitives are explained as:
a. send(P, message)- Send a message to process P.
b. receive(Q, message)- Receive a message from process Q.
A communication link in this scheme has the subsequent properties:
a. A link is established automatically in between every pair of processes which want to communicate. The processes need knowing only each other's identity to communicate.
b. A link is connected with exactly two processes.
c. Exactly one link exists in between each pair of processes.
With indirect communication, the messages are sent to and received from ports or mailboxes. All mailboxes have identification of uniqueness. In such scheme, a process can communicate along with some other process via numerous type mailboxes. There are two processes can communicate only if they share a mailbox. Both send and receive primitives are explained as follows:
a. send (A, message)- Send a message to mailbox A
b. receive (A, message)- Receive a message from mailbox A.
In such scheme, a communication link has the subsequent properties
a. A link is established in between a pair of processes only if both members of the pair have a shared mailbox.
b. A link may be connected with more than two processes.
c. A number of different links may exist in between each pair of communicating processes, along with each link corresponding to one mailbox.