pattern is the Push-pattern, the second one is the Request/Response-pattern;
the third one is the Subscribe/Notify-pattern, and the fourth one is the
Publish/Subscribe-pattern. All patterns are explained in the following.
Push
The Push-pattern (see Figure 44 ) is a one-way communication between two
parties in which a server sends data to a pre-defined client that receives the
data. The server hereby knows the address of the client beforehand and the
client is constantly awaiting messages from the server. The communication
channel in this pattern is pre-defined and meant to be applied in scenarios in
which the communication partners do not changed often. For example the
server can be a constrained device that sends data to a gateway dedicated to
this device. The gateway is listening constantly to the device and is consuming
the data received from this device.
Figure 44 : Push-pattern.The Request/Response-pattern (see Figure 45 and Figure 46 ) is a synchronous
way of communication between two parties. A client sends a request to a
server. The server will receive the request and will send a response back to the
client. The client is waiting for the response until the server has sent it.
Figure 45 : Request/Response-pattern for one client.The server needs some time to prepare the response for the client. In the
meanwhile another client might send a request. When the server is still busy
with preparing the response for the first client it cannot produce the response for
the second client. The second client will be placed into a queue until the server
is ready to prepare its response. Such scenario might lead to unacceptable
response times.