Server does not stores any information/reference/previous context
Every request is independent of each other
Request Response Communication Model
Each request involves setting up a new TCP connection
Header overhead
Not suitable for Real time application (RTA)
Web Socket
Statefull
Information like Session details, Open connection are stored
Full duplex
Single TCP connection
No Header overhead
Suitable for RTA
Message Queue Telemetry Transport (MQTT)
Uses Publisher-Subscriber model
Components
Publisher (Sensors)
Publishes to Broker
Subscriber (Application)
Subscribes to a particular topic using Broker
Broker
Publishes to subscriber based on the subscribed topic
Methods
Connect
Disconnect
Publish
Subscribe
Topic
Separated by slash => "value1/value2/value3"
Wild card
Single-level
"value1/+/value3" => Arbitrary values are allowed for value2
Multi-level
"value1/#" => Subscribing to a topic starting with "value1"
Advanced Message Queuing Protocol (AMQP)
Frame => Basic unit of data
Open => Open Connection
Begin => Begin session between two points
Attach => Attach a link
Transfer => Sending message over the link
Flow => Flow control
Disposition => Settlement regarding state of transfer
Detach => Detach a link
End => End session between two points
Close => Close Connection
Working
Publisher publishes message to Broker with a Routing key received by Exchange
Exchange routes it to one of the many Queues based on the Exchange type using Binding key
Message is then delivered to respective Consumer based on requirement
Exchange
Binding
Link between Exchange and Queues
Routing pattern is specified in binding
Exchange type
Direct
Routes the message to the Queue in which routing and binding key matches
Fanout
Routes the message to all the Queues bound to it
Topic
Routes the message to the Queue in which wild card matches routing key and routing pattern
Header
Routes the message based on message header attribute
Zigbee
IEEE 802.15.4 protocol is used in Physical & Data link layer
Zigbee protocol is defined for layer 3 and above (NL, TL, SL, PL, AL)
Network & Transport layer uses this protocol to define additional communication enhancements like authentication, security, encryption, forwarding, routing
Popularly used in Wireless sensor networks using MESH topology
Nodes
Zigbee Coordinator (C)
Monitors information related to network, nodes, transmission
Zigbee Router (R)
Routes the message to the neighboring nodes connected to it
Zigbee End Device (E)
Sleeps mostly
Low memory and cost requirement
Topology
Star
All "E" are connected with "C"
Cluster
All "R" are connected with "C" and all "E" are connected with "R"
