Edition 0 Updated to asp. Net core 0

Single-receiver message-based communication 
Message-
based asynchronous communication with a single receiver means there’s point
-to-point 
communication that delivers a message to exactly one of the consumers 
that’s reading from the 
channel, and that the message is processed just once. However, there are special situations. For 
instance, in a cloud system that tries to automatically recover from failures, the same message could 
be sent multiple times. Due to network or other failures, the client has to be able to retry sending 
messages, and the server has to implement an operation to be idempotent in order to process a 
particular message just once. 
Single-receiver message-based communication is especially well suited for sending asynchronous 
commands from one microservice to another as shown in Figure 4-18 that illustrates this approach. 
Once you start sending message-based communication (either with commands or events), you should 
avoid mixing message-based communication with synchronous HTTP communication. 
Figure 4-18. A single microservice receiving an asynchronous message 

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CHAPTER 3 | Architecting container and microservice-based applications 
When the commands come from client applications, they can be implemented as HTTP synchronous 
commands. Use message-based commands when yo
u need higher scalability or when you’re already 
in a message-based business process. 
Multiple-receivers message-based communication 
As a more flexible approach, you might also want to use a publish/subscribe mechanism so that your 
communication from the sender will be available to additional subscriber microservices or to external 
applications. Thus, it helps you to follow the 
open/closed principle
 in the sending service. That way, 
additional subscribers can be added in the future without the need to modify the sender service. 
When you use a publish/subscribe communication, you might be using an event bus interface to 
publish events to any subscriber.