Request-Response Pattern

From LID Wiki

A communications pattern that involves two parties, commonly referred to as the 'client' and the 'server'.

In this pattern, the 'client' initiates communication by sending a request to the 'server'. The 'server' then responds by sending a response back to the 'client'. The 'server' never initiates communications, but always responds to a request from the 'client'.

Of course, this pattern may be applied several times concurrently for a given software design. The pattern defines roles. Which object plays which role may change dynamically, and a given object may play several roles at the same time.