Notes.txt

## WiFi - HyperThink
   Password - hts@2018
   Wifi - HyperThings IoT
   Password - Things@18
   
   
1. What is protocol ?

A protocol is a set of rules and guidelines for communicating data. 
Rules are defined for each step and process during communication between two or more computers. 
Networks have to follow these rules to successfully transmit data.

2. What is TCP/IP protocol ?

TCP (Transmission Control Protocol) is a standard that defines how to establish and maintain a 
network conversation via which application programs can exchange data. TCP works with the 
Internet Protocol (IP), which defines how computers send packets of data to each other. 
Together, TCP and IP are the basic rules defining the Internet.

3. What is the OSI model ?

The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. 
	

## To kill all node process
	taskkill /im node.exe 
	or 
	taskkill /f /im node.exe

*** What is Polyfill :-
	A polyfill is a browser fallback, made in JavaScript, that allows functionality you expect to work in 
	modern browsers to work in older browsers, e.g., to support canvas (an HTML5 feature) in older browsers

*** Preset meaning :-
	Set or adjust (a value that controls the operation of a device) in advance of its use.
	
	
<<<<<<<<<<=======================================================================================>>>>>>>>>>>>>>>>>>>>>>>
#Path Module
The Path module provides a way of working with directories and file paths.
1.basename() - returns the filename part of a file path.
2.dirname() - returns the directories of a file path.
3.extname() - Returns the file extension of a path
4.format() - Formats a path object into a path string
5.isAbsolute() - Returns true if a path is an absolute path, otherwise false
6.join() - Joins the specified paths into one. eg; path.join('src', './app.js'); output - src\app.js
7.normalize() - Normalizes the specified path. eg; path.normalize('src///../app.js'); output - app.js
8.parse() - Formats a path string into a path object.
9.resolve() - Resolves the specified paths into an absolute path. eg; path.resolve('./app.js'); output - E:\Code\New folder\socket-io\src\app.js
10. What is path object - { root: 'E:\\',dir: 'E:\\Code\\New folder\\socket-io\\src.', base: 'app.js', ext: '.js',name: 'app' }


#HTTP Module
The HTTP module allows Node.js to transfer data over the Hyper Text Transfer Protocol (HTTP).
The HTTP module can create an HTTP server that listens to server ports and gives a response back to the client.
* To require http into project use -  var http = require('http');
* res.send is only in express and it is equivalent to res.write() and res.end() of node. It can automatically assign the Content-length 
HTTP response header field.
* use res.writeHead(200, { 'Content-Type': 'text/html' }); to include an HTTP header with the correct content type:
* use - req.url to get the url after domain name.


#File System Module
The Node.js file system module allows you to work with the file system on your computer.
* To require http into project use -  var fs = require('fs'); 
Common use for the File System module:

1. Read Files 
fs.readFile('demofile1.html', function(err, data) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.write(data);
    res.end();
  });
  
2. Create Files
The File System module has methods for creating new files:
    1. The fs.appendFile() method appends specified content to a file. If the file does not exist, the file will be created:
    2. The fs.open() method takes a "flag" as the second argument, if the flag is "w" for "writing", the specified file is 
		opened for writing. If the file does not exist, an empty file is created:
    3. The fs.writeFile() method replaces the specified file and content if it exists. If the file does not exist, 
		a new file, containing the specified content, will be created:
3. Update files 
	1. The fs.appendFile() method appends the specified content at the end of the specified file:
	2. The fs.writeFile() method replaces the specified file and content:
4. Delete Files
	The fs.unlink() method deletes the specified file:
5. Rename Files
	The fs.rename() method renames the specified file:

#URL Module
The URL module splits up a web address into readable parts.
* To require http into project use - var url = require('url'); 
Parse an address with the url.parse() method, and it will return a URL object with each part of the address as properties:

* What is a URL object ?
Url {
  protocol: 'http:',
  slashes: true,
  auth: null,
  host: 'localhost:8080',
  port: '8080',
  hostname: 'localhost',
  hash: null,
  search: '?year=2017&month=february',
  query: [Object: null prototype] { year: '2017', month: 'february' },
  pathname: '/default.htm',
  path: '/default.htm?year=2017&month=february',
  href: 'http://localhost:8080/default.htm?year=2017&month=february' }

#NPM 
* NPM is a package manager for Node.js packages, or modules if you like.
* The NPM program is installed on your computer when you install Node.js

* What is a Package?
	A package in Node.js contains all the files you need for a module.
	Modules are JavaScript libraries you can include in your project.
#Events
Node.js is perfect for event-driven applications.
Every action on a computer is an event. Like when a connection is made or a file is opened.
Node.js has a built-in module, called "Events", where you can create-, fire-, and listen for- your own events
In addition, all event properties and methods are an instance of an EventEmitter object. To be able to access 
these properties and methods, create an EventEmitter object:

var events = require('events');
var eventEmitter = new events.EventEmitter(); 


#Net Module
The Net module provides a way of creating TCP servers and TCP clients.
* To require http into project use - var net = require('net');
* Method 	Description
1. connect() - Creates a new connection to the server, and returns a new Socket
2. createConnection() - Creates a new connection to the server, and returns a new Socket
3. createServer() - Creates a new server
4. isIP - Checks if the specified value is an IP address
5. isIPv4 - Checks if the specified value is an IPv4 address
6. isIPv6 - Checks if the specified value is an IPv6 address

#Util Module
The Util module provides access to some utility functions.
The syntax for including the Util module in your application: var util = require('util');

#VM Module
The VM module provides a way of executing JavaScript on a virtual machine, almost like eval() in JavaScript.
The syntax for including the VM module in your application: var vm = require('vm');

#Zlib Module
The Zlib module provides a way of zip and unzip files.
The syntax for including the VM module in your application: var zlib = require('zlib');

#TLS Module
The TLS module provides a way of implementing TLS (Transport Layer Security) and SSL (Secure Socket Layer).
The syntax for including the TLS module in your application: var tls = require('tls');

#Stream Module
The Stream module provides a way of handling streaming data.
There are two types of streams: readable and writeable.

An example of a readable stream is the response object you get when working with the http.createServer() method.

An example of a writable stream is the request object you get when working with the http.createServer() method.

#Buffer Module
The buffers module provides a way of handling streams of binary data.
The Buffer object is a global object in Node.js, and it is not necessary to import it using the require keyword.

<<<<<<<<<=================================================================================================================>>>>>>>>>


*** MongoDB configuration needs to be set after custom installation 
	We must specify db and log path after installation
	Go to MongoDB directory and bin
	mongod --directoryperdb --dbpath "C:\Program Files\MongoDB\Server\4.0\data" --logpath "C:\Program Files\MongoDB\Server\4.0\log\mongo.log" --logappend --install
*** Mongo DB Dump 
	** If you are using Windows Power shell the prefix < ./ > before each command
	mongodump --host <localhost or IP> --port 27019 ( It will create dump directory in same directory )
	mongodump --host localhost --port 27019 --out "E:/Folder/folder" ( It will push the dump in given directory path)
	mongodump --host localhost --port 27019 --out "E:/Folder/folder" --db test ( It will only dump the specified databse )
	mongodump --host localhost --port 27019 --out "E:/Folder/folder" --collection users --db test ( It will only dump users collection from test database)
	mongodump --host mongodb1.example.net --port 3017 --username user --password "pass" --out /opt/backup/mongodump-2013-10-24 (If username password is requred)
	
*** Mongo DB Restore
	mongorestore --port 27017 <path to the backup> (It will restore the db from the backup path)
	mongorestore dump-folder/ (It will restore the db from dump-folder to mongodb running at default port 27017)
	mongorestore --host mongodb1.example.net --port 3017 --username user --password 'pass' "E:/Folder/folder" ( It will restore db to given remote location)

<<<<<<<<<=================================================================================================================>>>>>>>>>

##RESTful Constraints
	1. Client-Server Architecture
		Seperation od concerns RESTful API should not care about the UI.
	2. Stateless
		No Client-Context (e.g. Session) is stored on the server.
	3. Chachebility 
		Responses nust define themselves as cachable or non-cachable.
	4. Layred system
		Intermediate servers may be used without the client knowing about it.
	5. Unifotm Interface
		Resources are identified in requests, transfered data is decoupled form db schema. Self destructive messages links to further resoureces.
	6. Executable code on demand
		Executable code could be transfered.
##CORS - Cross Origin Resource Sharing
##Node JS Setup
1. Install Node JS from (https://nodejs.org/en/). Bette to download version with LTS support.
2. npm init ( to create intialize npm and create package.json, it will ask few things to enter like version, author etc )
3. npm init y ( just to avoid the wizard and directly creating package.json)
4. npm install <package name> --save (In the latest version no need to use --save, package will be automatically saved to as a dependencies 
5. npm i <package-name>
6. npm i --save-dev <package-name> ( It will install the package as dev dependencies)
NPM Libraries 
1. Frameworks
	1. Express
	2. HAPI
	3. Restify
	4. Koa
	5. Sails JS (MVC)
2. nodemon - to automatically styart server after any changes
3. morgan - to make a log 
4. body-parser - to parse the body(it supports json,urlencoded, doennot support files)
5. cors - CORS helper
6. MongoDB package
	1. mongoose
	2. mongojs
	3. waterline
7. Logging Libraries
	1. Winston
	2. Bunyan
	3. Log4js
	4. Morgan
8. File Upload Libraries
	1. Multer
	2. Formidable
9. MQTT
	1. mqtt js
	2. paho-mqtt
	3. mqtt-server
	4. ioBroker MQTT
10. Modbus	
	1. jsmodbus
	2. modbus-tcp
	3. node-modbus
11. AngularJS service to handle Rest API
	1. Restangular
	2. Satellizer
12. ORM for MySQL/Postgres etc
	1. Sequelize
13. Client-side HTTP request library
	1. axios
	2. superagent
14. Mail 
	1. nodemailer





## NODE-RED 
1. Install node red using < npm install -g --unsafe-perm node-red > command
2. Install node red dashboard < npm install node-red-dashboard>
3. run <node-red> to run the node-red


## Hyper V
Hyper-V is Microsoft's hardware virtualization product. It lets you create and run a 
software version of a computer, called a virtual machine. Each virtual machine acts like a 
complete computer, running an operating system and programs. When you need computing resources, 
virtual machines give you more flexibility, help save time and money, and are a more efficient way 
to use hardware than just running one operating system on physical hardware.


<<<<<<<<<==============================================================================>>>>>>>>>>>>>>
## IoT Platform
1. Kaa
2. ThingsBoard https://thingsboard.io/
3. DeviceHive https://devicehive.com/
4. https://iotivity.org/
5. https://www.particle.io/
6. http://www.iot-dsa.org/
7. Sitewhere - https://sitewhere.io/en/
8. ARM - https://www.arm.com/
9. Cumulocity - https://www.softwareag.cloud/site/product/cumulocity-iot.html#/
10. Thinger - https://thinger.io/
11. Bolt IoT - https://www.boltiot.com/
12. Webnms - https://www.webnms.com/
13. Firendly IoT - https://www.friendly-tech.com/
14. Hologram IoT - https://hologram.io/
15. IBM - https://www.ibm.com/internet-of-things
16. Azure - https://azure.microsoft.com/en-in/services/iot-hub/
17. At & T - https://iotplatform.att.com/
18. Predix - https://www.predix.io/
19. ThingsSpeak - https://thingspeak.com/
20. Zetta - https://www.zettajs.org/
21. DevicePiolt - https://www.devicepilot.com/
22. Thethings.iO - https://thethings.io/
23. https://ubidots.com/
24. https://temboo.com/
25. https://artik.cloud/
26. https://xively.com/
27. https://mydevices.com/

<<<<<<<<<==============================================================================>>>>>>>>>>>>>>>

## Tool To Explore
1. Kubernetes( https://kubernetes.io/ ) - Kubernetes (K8s) is an open-source system for automating deployment, scaling,
   and management of containerized applications.
2. Docker
3. Chocolatey( https://chocolatey.org/ ) - The package manager for Windows
4. https://dweet.io/
5. https://freeboard.io/
7. Grafana
8. Library.io
9. Node-RED 
10. CMD Tools - Babun/Cygwin/Chocolatey/

<<<<<<<<<==============================================================================>>>>>>>>>>>>>>>>>

## Naming Convenstions
	File Name - lowercase and seprated with dashes
	Variable - camelCase
	
## Few Node Commands
	1. node --version - to check node version
	2. npm --version - to check npm verison
	3. npm i -D - to install library with dev dependencies
	4. npm i -D @babel/core  babel-loader @babel/preset-env



<<<<<<<<<==============================================================================>>>>>>>>>>>>>>>>>
##Docker Commands

1. Check Docker veriosn
	docker --version
2. To run a image
	docker run <image-name> eg; docker run hello-world
3. To check all the images, which is in the system
	docker images
4. To pull a image from docker hub
	docker pull <image-name> eg; docker pull ubuntu
5. To run a image
	docker run -it -d <image-name> eg; docker run -it -d ubuntu
6. To show all the containers
	docker ps -a
7. To access a running container
	docker exec -it <containerId> bash. eg; docker exec -it 72d89f31ef49 bash
8. To come out of container
	exit
9. To stop a container
	docker stop <containerId> eg; docker stop 72d89f31ef49
10.  To login
	docker login
11. To commit i.e. To create a image in local system
	docker commit <containerId> <docker-hub-repository>
12. To push the image to docker hub
	docker push nikhil/ubuntu
13. To delete a container
	docker rm <containerId> eg; docker rm 72d89f31ef49
14. To delete docker images
	docker rmi <imageId> eg; docker rmi 4c108a37151f
15. To create a DokerFlle where all the dependencies live
	touch DockerFile
16. To build the image 
	docker build -t <folder-name> . eg; docker build -t docker-node .
17. To run the docker container
	docker run -p 	8082:3001 <folder-name> eg; docker run -p 8082:3001 docker-node
	
	
	
# Encryption/Cryptography :-
 
* Encryption Algorithms - 1. Symmetric or Secret key Encryption 2. Asymmetric or Public key encryption
* Cipher - Non readable

* Cryptography - 1. Symmetric Key Cryptography 	2. Asymmetric Key Cryptography
* Symmetric Key Cryptography - 1. Classical Cryptography 	2. Modern Cryptography
* Classical Cryptography - 1. Transposition Cipher 2.Substiution Cipher
* Modern Cryptography - 1. Stream Cipher 2. Block Cipher

* AES - Advanced Encryption Standards
* DES - Data Encryption Standards

<<<<<<<<<=================================================================================================================>>>>>>>>>
#OPEN SSL
* Create private key - openssl genrsa -out mykey.pem 1024 		then 		cat mykey.pem
* Create Certificate using the above private key - openssl req -new  -key mykey.pem -out mykey-csr.pem
* Generate self signed certificate - openssl x509 -req -in mykey-csr.pem -signkey mykey.pem -out my-cert.pem
* Connecting using openssl - openssl s_client -connect localhost:8000
**Steps to create the server certificate
1. To create new certificate authority



2. To create private key for server
	openssl genrsa -out server-key.pem 4096

3. To generate the certificate signing request
	openssl req -new -key server-key.pem -out server-csr.pem

4. To sign the request
	openssl x509 -req -days 9999 -in server-csr.pem -CA ca-crt.pem -CAkey ca-key.pem -CAcreateserial -out server-crt.pem

** Steps to create client certificate
1. To create client key
 openssl genrsa -out client1-key.pem 4096
 
2. To create a pair of certificate signing requests.
	openssl req -new -key client1-key.pem -out client1-csr.pem

3. To sign our two new client certs
	openssl x509 -req -days 999 -in client1-csr.pem -CA ca-crt.pem -CAkey ca-key.pem -CAcreateserial -out client1-crt.pem

** TO verify evrything worked perfectly
	openssl verify -CAfile ca-crt.pem client1-crt.pem

** To run mosquitto broker and load the configuration files
	1. Go to mosquitto installation folder
	2. mosquitto -v -c mosquitto.conf

<<<<<<<<<=================================================================================================================>>>>>>>>>

#Socket Programming
* Why - To build any networked application.
* Bidirectional data flow i.e. from client to server and server to client. Allows real time data flow 
* It is a wrapper around websockets.



# Websockets
* Bi directional communication.
* In websockets connection doesnt get closed untill the client or server terminate the connection.
* Chat application




<<<<<<<<<===============================================================================================================>>>>>>>>>>>>>>>>>>


#Modbus
Modbus is a serial communication protocol. Modbus can be used over ethernet as well as a serial cable.
Modbus protocol is defined as a master/slave protocol, meaning a device operating as a master will poll 
one or more devices operating as a slave. This means a slave device cannot volunteer information; 
it must wait to be asked for it. The master will write data to a slave device’s registers, and read 
data from a slave device’s registers. A register address or register reference is always in the context of 
the slave’s registers.
Each exchange of data consists of a request from the master, followed by a response from the slave.
In the TCP context, the slave becomes the server and the master becomes the client. 
The types of registers referenced in Modbus devices include the following:
• Coil (Discrete Output) - Coils are 1-bit registers, are used to control discrete outputs, and may be read or written.
• Discrete Input (or Status Input) - Discrete Inputs are 1-bit registers used as inputs, and may only be read.
• Input Register - Input registers are 16-bit registers used for input, and may only be read.
• Holding Register - Holding registers are the most universal 16-bit register, may be read or written, and may be 
used for a variety of things including inputs, outputs, configuration data, or any requirement for "holding" data.

#Modbus Function Codes Recognized by CSI Gateways
Function Code 	Register Type
1 				Read Coil
2 				Read Discrete Input
3 				Read Holding Registers
4 				Read Input Registers
5 				Write Single Coil
6 				Write Single Holding Register
15 				Write Multiple Coils
16 				Write Multiple Holding Registers

#MQTT
	It is a simple light wieght publish and subscribe system, where we can recive and publish messages as a client.
	You can send a command to control an output
# Register
A processor register (CPU register) is one of a small set of data holding places that are part of the computer processor.


<<<<<<<<<==================================================================>>>>>>>>>>>>

# Certificate file formats
* What is DER file ?
	Distinguished file format. Binary format. Non human readable.Perfect for an X.509 certificate

* What is PEM file ?
	A file with the PEM file extension is a Privacy Enhanced Mail Certificate file used to privately transmit email.
	Generally the format provided by CAs.
	The PEM format has been replaced by newer and more secure technologies but the PEM container is still 
	used today to hold certificate authority files, public and private keys, root certificates, etc.

*Whhat is PKCS #12 file ?
	Public key Cryptography Standards #12. This is personal information exchange syntax standards. It is used to put together a pulic key and 
	private key and send them to someone else. In windows similar format is (.pfx).


*What is CER file ?
	This is a certificate file.This is usually holding the X.509 standard certificate.
	Can be encoded as binary DER file format or the ASCII PEM format. It contains the public key. Common format for windows certificate. 
	(.cer) extension.


* What os CRT file ?
	CRT is a file extension for a digital certificate file used with a web browser. CRT files are used to verify a secure website's authenticity, 
	distributed by certificate authority (CA) companies such as GlobalSign, VeriSign and Thawte.


*PKCS #7

#Types of Certificate
Certificate, in a nutshell, is a file that binds the owner identity with his public key. this bond is 
signed and confirmed by a reliable third party which called the Certificate Authority (CA). 
You can think of the certificate authority as a trusted organization whose customers are 
web-services owners that need to issue a certificate. 

* Root certificate 
	The public key certificate that identifies the root CA(Certificate Authority). Everything starts with this certificate.
	This certificate will issue other certificate.
	Access to the root certificate allows for the creation of any trsuted certificate. If someone gets the private key associated with this
	CA then they can access their own certificates.

* Web server SSL certificate.
* Domain validation certificate(DV).
	Owner of this certificate has some control over a DNS domain.
* Extended validation certificate (EV).
	Green name of the owner on the address bar. Additional checks have verified the certificate owners identity.

* Subject alternative name (SAN)
	Extension to X.509 certificate. Many domains can have exactly the same certificate.	

* Self signed certificate
	Internal certificates dont need to be signed by a public CA.
	Your company is the only one going to use it.
	No need to purchase trust for devices that already trust you.
	Bulid your own CA
	Issue your own certificates signed by your own CA.
	Install the CA certificate/trusted chain on all devices


* User certificate

* Email Certificate
	Use Cryptography in an email platform
	Encrypting email.
	Digital signatures

* Code siging certificate
* CSR extension file - Certificate signing request
	A CSR file is a file created as a signing request for a digital certificate. 
	It contains an encrypted block of text that identifies the applicant of the certificate and 
	includes encrypted data for country, state, organization, 
	domain, email address, and public key. The file is used by a Certificate Authority to establish proof of identity for Web sites.

* PKI - Public key infrastructure
* X.509 
	An X.509 certificate is a digital certificate that uses the widely accepted international 
	X.509 public key infrastructure (PKI) standard to verify that a public key belongs to the user,
	computer or service identity contained within the certificate.
	
	
	
<<<<<<<<<<<<<<<<====================================================>>>>>>>>>>>>>>>>>>>>>

#OpenSSL Commands
Generate a certificate authority certificate and key
openssl req -new -x509 -days duration -keyout mqtt_ca.key -out mqtt_ca.crt

Generate a server key
openssl genrsa -des3 -out mqtt_server.key size_of_private_key_in_bits

Generate a certificate signing request to send to the CA
openssl req -out mqtt_server.csr -key mqtt_server.key -new

Send the CSR to the CA, or sign it with your CA key
openssl x509 -req -in mqtt_server.csr -CA mqtt_ca.crt -CAkey mqtt_ca.key -CAcreateserial -out mqtt_server.crt -days duration

Generate a client key
openssl genrsa -des3 -out mqtt_client.key size_of_private_key_in_bits

Generate a certificate signing request to send to the CA
openssl req -out mqtt_client.csr -key mqtt_client.key -new

Send the CSR to the CA, or sign it with your CA key
openssl x509 -req -in mqtt_server.csr -CA mqtt_ca.crt -CAkey mqtt_ca.key -CAcreateserial -out mqtt_server.crt -days duration

Configure mosquitto file

port 8883
cafile your_path/mqtt_ca.crt
certfile your_path/mqtt_server.crt
keyfile your_path/mqtt_server.key
require_certificate true  //set it if you want to verify client's certificate
tls_version tlsv1.1

<<<<<<<<<<<<<<<<<<<<<<===============================================>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
* Statelessness -
As per the REST (REpresentational “State” Transfer) architecture, the server does 
not store any state about the client session on the server side. This restriction 
is called Statelessness. Each request from the client to server must contain all 
of the information necessary to understand the request, and cannot take advantage 
of any stored context on the server. Session state is therefore kept entirely on the client. 
client is responsible for storing and handling all application state related information on client side.

Statelessness means that every HTTP request happens in complete isolation. 
When the client makes an HTTP request, it includes all information necessary for 
the server to fulfill that request. The server never relies on information from previous requests. 
If that information was important, the client would have sent it again in this request.

* What is Multi tenant Architecture ?
Multi-tenant architecture, commonly referred to as multitenancy, is a software architecture in 
which multiple single instances of software run on a single physical server. 
The server then serves multiple tenants.

* Service-oriented architecture ?
Service-oriented architecture is a style of software design where services are 
provided to the other components by application components, through a communication protocol over a network.

*SaaS
Software as a service is a software licensing and delivery model in which software is licensed on a 
subscription basis and is centrally hosted. It is sometimes referred to as "on-demand software",.

* IaaS
Infrastructure as a service (IaaS) is a form of cloud computing that provides virtualized computing resources over the internet.

*PaaS
Platform as a service (PaaS) is a cloud computing model in which a third-party provider delivers hardware 
and software tools -- usually those needed for application development -- to users over the internet. 
A PaaS provider hosts the hardware and software on its own infrastructure.


* The various approached to multi tenancy 
	1. Shared database with shared schema
		A single database keeps every tenant’s data. A ForeignKey in the tables identifies the tenant.
		
	2. Shared database with isolated schema
		A single database keeps every tenant’s data. Each tenant’s data is in a separate schema within the single database. 
		The schema identifies the tenant and data tabled do no have a FK to the tenant.
		
	3. Isolated database with a shared app server
		Every tenant’s data is in a separate database. The database identifies the tenant.
	
	4. Completely isolated tenants using Docker
	
* Mult-tenancy is regarding to the data ownership. The data is segmented by tenans (owners). 
The application use to be the same for a simple reason: economy of scale. The data storage 
could be also the same or it could be different for each tenan. 
The data is not shared-accesible among tenants (or usually they are not, so far I know)