Request–response

It is analogous to a telephone call, in which the caller must wait for the recipient to pick up before anything can be discussed.This is a simple but powerful messaging pattern which allows two applications to have a two-way conversation with one another over a channel; it is especially common in client–server architectures.[1] Request–response pattern can be implemented synchronously ( such as web service calls over HTTP) or asynchronously.[1] In contrast, one-way computer communication, which is like the push-to-talk or "barge in" feature found on some phones and two-way radios, sends a message without waiting for a response.(Most of these systems use a "listen before talk" or other contention-based protocol so multiple sensors can transmit periodic updates without any pre-coordination.)
computer sciencecomputersnetworkmessage exchange patterntelephone callapplicationschannelclient–serversynchronouslyasynchronouslypush-to-talktwo-way radiosfieldbusCAN buscontention-based protocolFutures and promisesPublish/subscribeRemote procedure call