April 2018
Intermediate to advanced
248 pages
5h 31m
English
Content preview from Internet of Things with Raspberry Pi 3
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Persistent sessions
When a client connects to the broker, it subscribes to certain topics on which it wants to receive messages from the broker. If the client disconnects from the broker, then on reconnect it has to subscribe to all the topics again, which can be a burden for resource-constrained clients. This can be overcome by using a persistent session, which saves all the relevant client-related information on the broker and in the case of reconnection it helps to retain all subscriptions of the client. A client session is stored with respect to clientId. The following information is stored in a session:
- All subscriptions
- All messages with QoS 1 and 2 that are not yet acknowledged by the client
- All QoS 1 and 2 messages that the client ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.