MEP (Message Exchange Pattern) is a way of communicating between clients and servers in WCF. MEP is one of the greatest features of WCF. The three types of MEPs supported by WCF are as follows:
Request-Reply : Request-Reply is WCF's default communication pattern.
One-way : Using this pattern means you don't expect to receive a response back from the service after it performs a certain operation.
Duplex : Duplex is a two-way communication way. The duplex MEP is applicable when the client initiates a long-running process with the service and the service requires notification.
