In the previous tutorial, a basic architecture of an IOT system was discussed. From the discussions in the previous tutorial, it must be clear that communication network is the backbone of any IOT system. It is only the (internet) network that enables IOT devices (boards) and cloud based services and applications to communicate with each other. Without internet network, IOT is nothing. Data communication on an internet network is not as straight forward. There are myriad of heterogeneous devices connected over internet and these plethora of unique devices need to communicate in a secure, reliable and routed fashion.

In the previous tutorial, reference architecture for IOT was compared with OSI and TCP-IP models and various data communication protocols for different layers of IOT architecture were mentioned. In this tutorial, the physical and data link layer protocols will be discussed in details. The physical and data link layer comprises of the IOT objects and physical networks connecting them with other objects or network.  

In the previous tutorial, various physical and data link layer protocols specified for computers and mobile devices were discussed. Continuing the subject of physical and data link protocols, in this tutorial, network access protocols specified for LPWAN will be discussed. LPWAN stands for Low Power Wide Area Network. In general, LPWAN is a low power long range wireless network in which battery powered IOT devices surrounded by wireless sensors (Wireless Sensor Network) are interconnected.

In the previous tutorial, various physical and media access control (MAC) protocol for Personal Area Network (PAN), Home Area Network (HAN) and Local Area Network (LAN) were discussed. In this tutorial, physical and MAC protocols based on RFID and mobile standard will be discussed. There are the following RFID based protocol stacks: RFID, DASH7, NFC.There are the following common mobile standards which are evolving to accommodate IOT applications

In the previous tutorial, the basics of Ethernet technology were discussed. In this tutorial, the Ethernet technology will be used to connect an Arduino board over internet with a PC. The Arduino based IOT device and the PC will be setup to communicate using MQTT protocol via HiveMQ Broker.  An IOT device based on Arduino will be designed in this project. The Arduino will be interfaced with an Arduino Ethernet Shield to connect with a router via Ethernet cable (Cat 5e).  

SIM800 is a popular GSM GPRS modem. It supports General Packet Radio Service (GPRS) for connecting to the Internet. This module has built-in TCP/IP stack that can be accessed serially with AT commands.The modem needs to be configured by connecting it to a PC. In such setup, the SIM800 modem with SIM card acts as TCP client and the PC  acts as TCP server.  

In the previous tutorial, the Ethernet technology was used to connect an Arduino based IOT device with the internet network. The IOT devices can also be connected to internet network using mobile technologies like GSM, CDMA and GPRS. There are two major technologies for data transfers over cellular networks – GSM and GPRS. These two technologies differ from each other on the basis of data rates and the charges they take for their operation. 

In the previous tutorial, ESP8266 module was used to design a Home Area Network to control an LED light from a remote PC. The PC client was used to send control signals to switch on and off the LED light in the Home Area Network. In this tutorial, the ESP module will be interfaced with DHT-11 temperature sensor and temperature  data will be sent to the PC client for real-time temperature monitoring. In this project, instead of LED, the DHT-11 sensor will be interfaced with the ESP8266 on ESP Client side.

Security is a prime concern in any IoT application development. The data from the IoT devices is passed to the server/cloud where it may be stored temporarily or for long time to generate analytics. The transportation medium through which the data is passed from the IoT device to the cloud must be secured with implementation of various IoT security measures, so that the data could not be hacked by any Man-in-the-Middle attack.  

In the previous tutorial, it was learnt that how a smart phone and a PC can be set up as MQTT clients and their connection with an MQTT broker can be established. The smart phone was configured as an MQTT client using an android MQTT app – IOT MQTT Dashboard while the PC was configured as MQTT client using a chrome add-on – MQTTLens.Now, in this tutorial, these MQTT clients – Mobile and PC will be made to communicate with each other using MQTT protocol. The communication between the MQTT clients is only possible via MQTT broker.

Internet of Things is meant to empower objects of day to day use with embedded electronics and IT infrastructure. It aims to connect these objects in real time with the internet network and allow them to communicate with other co-located or remote objects. For communicating with each other, the IOT devices need to follow protocols. An application developer need to take care primarily of the implementation of application layer protocols while usually the implementation of network and transportation layer protocols remain at the hand of network administrators or network programmers.

Application layer refers to OSI Level 5, 6 and 7. It is application layer in the TCP-IP model. In IOT architecture, this layer lies above the service discovery layer. It is highest layer in the architecture extending from the client ends. It is the interface between the end devices and the network. This layer is implemented through a dedicated application at the device end. Like for a computer, application layer is implemented by the browser. It is the browser which implements application layer protocols like HTTP, HTTPS, SMTP and FTP. Same way, there are application layer protocols specified in context to IOT as well.

In the previous tutorial, installation and configuration of RSMB Broker for MQTT-SN protocol implementation was discussed. In this tutorial, two devices will be setup to communicate over MQTT-SN protocol using RSMB Broker. One of these devices will be configured as MQTT-SN Client and other as the MQTT-SN Server.  The MQTT-SN needs a gateway when WSN (Wireless Sensor Network) devices want to send data to MQTT server which run on TCP/IP protocol or want to communicate with MQTT clients.

In the previous tutorial, communication between two PCs was setup over Zigbee Protocol using Xbee modules and XCTU software. In this tutorial, two Xbee module based IoT devices will be designed and configured to communicate with each other over Zigbee protocol. One of these devices in the Zigbee network will be a Coordinator device and the other will be a Router device. The coordinator device will control LED interfaced at the Router device. 

In the previous tutorial, IoT communication between two devices over Zigbee protocol was demonstrated using two Xbee modules. The two modules were communicating with each other automatically without any human intervention. The two modules were also operating in transparent mode in the previous project.  In this project, an LED light controller is designed where one device controls the LED interfaced at other by communicating data in API mode. In this tutorial, two Xbee module based IoT devices will be designed and configured to communicate with each other over Zigbee protocol

In the previous tutorial, basics of MQTT-SN protocol were discussed. It was mentioned that an MQTT-SN Gateway needs to communicate with an MQTT-SN Broker. The MQTT-SN brokers are little different from MQTT Brokers. Really Small Message Broker is one of the popular MQTT-SN brokers. Really small message broker (aka RSMB) is a light-weight, low-overhead messaging MQ telemetry transport broker (version 3 or 3.1) or MQTT-SN broker. It is a pub/sub based broker. It allows messaging to and from tiny devices such as sensors and actuators over networks that are constrained in terms of low bandwidth, limited processing capabilities and varying reliability. 

In the previous tutorial, features, advantages and limitations of TCP/IP Protocol were discussed. Though, TCP/IP is not best suited for IoT applications due to packet overheads, still being the most common protocol stack on internet, it offer ubiquitous connectivity. An IoT device can be made to communicate with a cloud or server using TCP/IP protocol without any hassle of network programming and network administration. In this project, an IoT device will be designed that could transmit sensor data to ThingSpeak Platform using the TCP/IP protocol.  

The TCP/IP protocol despite being most common protocol stack on internet is not much suitable for IoT applications due to large overhead. It is more suitable for applications where reliable delivery of data with high bandwidth in hand is required. The IoT applications generally have limited bandwidth and need swift transfer of small data packets. In such case, the UDP/IP stack is far better than TCP/IP.The User Datagram Protocol (UDP) is the simplest transportation layer protocol used primarily for establishing low-latency and loss tolerating connections between applications on the communication network.

In the previous tutorials, MQTT protocol packets and MQTT security mechanisms were discussed. Now it’s time to start getting hands dirty. For creating a communication network in which multiple IoT devices can communicate with each other via a MQTT broker, it is important to configure IoT devices as MQTT clients. The MQTT is developed on the top of TCP/IP stack, so the devices must have TCP/IP stack with them if they want to communicate to each other via MQTT broker.