0. Intro

Application-layer protocol

• It defines:
  1. the types of messages exchanged
  2. the syntax of the various message types
  3. the semantics of to field
  4. rules for determining when and how a process sends messages and responds to messages

Client-Server Pattern

Client:

• Initiate the request
• Come and go:
  • send req
  • receive resp
  • terminate

Server:

• Always on
• Running on well-known ports
• Passive:
  1. wait for req from clients at a fixed location
  2. process received req
  3. send resp

methods of inter-process communication (IPC)

• Memory sharing: multiple processes access the same segment of memory

  Faster but more complex:

  • no need to copy data between processes
  • require careful management of synchronization

• Message passing: processes communicate with each other by sending and receiving messages through a communication channel (e.g. pipes, sockets, mq)

socket interface

• The API between the application layer and the transport layer
• A set of instructions locates between the OS and the application program