NtpClient

Source: Enable Windows NTP Client

Source: AnyConnect Secure Mobility Client v4.9.0195 – Windows, Mac, Linux

Source: Install Cisco AnyConnect on Ubuntu / Debian / Fedora | ComputingForGeeks

Modbus is a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices.^[1] Modbus is popular in industrial environments because it is openly published and royalty-free. It was developed for industrial applications, is relatively easy to deploy and maintain compared to other standards, and places few restrictions – other than the datagram (packet) size – on the format of the data to be transmitted. Modbus uses the RS485 or Ethernet as its wiring type. Modbus supports communication to and from multiple devices connected to the same cable or Ethernet network. For example, a device that measures temperature and a different device to measure humidity, both of which communicates the measurements to a computer.

Modbus is often used to connect a plant/system supervisory computer with a remote terminal unit (RTU) in Supervisory Control and Data Acquisition (SCADA) systems in the electric power industry. Many of the data types are named from industrial control of factory devices, such as Ladder logic because of its use in driving relays: A single physical output is called a coil, and a single physical input is called a discrete input or a contact.

The development and update of Modbus protocols have been managed by the Modbus Organization since April 2004, when Schneider Electric transferred rights to that organization. The Modbus Organization is an association of users and suppliers of Modbus-compliant devices that advocates for the continued use of the technology.

Source: Modbus – Wikipedia

sudo chsh -s /bin/bash <username>

Source: command line – Arrow keys, Home, End, tab-complete keys not working in shell – Ask Ubuntu

The application/x-www-form-urlencoded Content-type header is not needed. Unless the request handler expects the parameters coming from request body. Try it out:

curl -X DELETE "http://localhost:5000/locations?id=3"

or

curl -X GET "http://localhost:5000/locations?id=3"

Source: http – CURL Command Line URL Parameters – Stack Overflow

https://en.m.wikipedia.org/wiki/Carlos_Ch%C3%A1vez

curl –silent –output /dev/null http://example.com

Source: Hide curl output – Unix & Linux Stack Exchange

• Add a splash screen, the very first thing your users see after they select your app.
• Use AppLoading to ensure your interface is ready before the user sees it.
• Preload and cache your assets so your app loads quickly, even with a poor internet connection.

• Configure the status bar so it doesn’t clash with your interface.
• Use native gestures whenever possible.
• Use interface elements that make sense on the device. For example, see the iOS Human Interface Guidelines.

• Add a great icon. Icon requirements between iOS and Android differ and are fairly strict, so be sure and familiarize yourself with that guide.
• Customize your primaryColor.
• Make sure your app has a valid iOS Bundle Identifier and Android Package. Take care in choosing these, as you will not be able to change them later.

• version will apply both to iOS and Android. For iOS, this corresponds to CFBundleShortVersionString, and for Android this corresponds to versionName. This is your user-facing version string for both platforms.
• android.versionCode functions as your internal Android version number. This will be used to distinguish different binaries of your app.
• ios.buildNumber functions as your internal iOS version number, and corresponds to CFBundleVersion. This will be used to distinguish different binaries of your app.

• Use Constants.nativeAppVersion to access the version value listed above.
• Use Constants.nativeBuildVersion to access either android.versionCode or ios.buildNumber values (depending on the current platform)

• Starting October 3, 2018, all new iOS apps and app updates will be required to have a privacy policy in order to pass the App Store Review Guidelines.
• Additionally, a number of developers have reported warnings from Google if their app does not have a privacy policy, since by default all Expo apps contain code for requesting the Android Advertising ID. Though this code may not be executed depending on which Expo APIs you use, we still recommend that all apps on the Google Play Store include a privacy policy as well.

• All apps in the iTunes Store must abide by the App Store Review Guidelines.
• Apple will ask you whether your app uses the IDFA, the answer is “yes.” This is because Expo contains the Facebook and Branch SDKs, which contain code for collecting the IDFA, and you’ll need to check a couple boxes on the Apple submission form. See Branch’s Guide for which specific boxes to fill in.

Note: No data is sent to Branch, Facebook, Segment, or Amplitude from your app unless you explicitly do so using the APIs. For more information on how Expo handles your data, and your end users’ data, take a look at our Privacy Explained page.

• Permissions are configured via the android.permissions key in your app.json file
• By default, your app will include all permissions supported by Expo. This is so that your standalone app will match its behavior in the Expo client and simply “work out of the box” no matter what permissions you ask for, with hardly any configuration needed on your part.
• There are some drawbacks to this. For example, let’s say your To-do list app requests CAMERA permission upon installation. Your users may be wary of installing since nothing in the app seems to use the camera, so why would it need that permission?
• To remedy this, simply add the android.permissions key in your app.json file, and specify which permissions your app will use. A list of all Android permissions and configuration options can be found here.
• To use only the minimum necessary permissions that Expo requires to run, set "permissions" : []. To use those in addition to CAMERA permission, for example, you’d set "permissions" : ["CAMERA"].

• It’s helpful to glance over Common App Rejections.
• Binaries can get rejected for having poorly formatted icons, so double check the App Icon guide.
• Apple can reject your app if elements don’t render properly on an iPad, even if your app doesn’t target the iPad form factor. Be sure and test your app on an iPad (or iPad simulator).
• Occasionally people get a message from Apple which mentions an IPv6 network. Typically this is just Apple’s way of informing you what kind of network they tested on, and the actual “IPv6” detail is a red herring. All of Expo’s iOS code uses NSURLSession, which is IPv6-compatible. More info.

"infoPlist": {
  "NSCameraUsageDescription": "This app uses the camera to scan barcodes on event tickets."
},

  "expo" : {
    ...
    "ios" : {
      "infoPlist": {
        "CFBundleAllowMixedLocalizations": true
      }
    },
    "locales": {
      "ru": "./languages/russian.json"
    }
  }

// russian.json
{
  "CFBundleDisplayName": "Привет",
  "NSContactsUsageDescription": "Эти слова по русски"
}

Source: Deploying to App Stores – Expo Documentation

Source: Building Standalone Apps – Expo Documentation

<VirtualHost *:80>
    ServerName domain.org
    ServerAlias www.domain.org

    ProxyPass /blog !
    Alias /blog /var/apache-vhosts/www.domain.org-blog

    <Directory /var/apache-vhosts/www.domain.org-blog/>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride All
        Order allow,deny
        allow from all
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/error.log

    # Possible values include: debug, info, notice, warn, error, crit,
    # alert, emerg.
    LogLevel warn
    CustomLog ${APACHE_LOG_DIR}/access.log combined


    ProxyPass / http://localhost:8884/
    ProxyPassReverse / http://localhost:8884/
    ProxyPreserveHost on
    LogLevel debug
</VirtualHost>

Source: node.js – how to achieve an apache Alias with a proxy pass on the same domain – Stack Overflow

Yes, you have learned React and now you can develop a full-fledged front end application. The create-react-app helps you to set up and run a React project, including it code transpiling, basic linting, testing, and build systems. In short, you can start writing React code with minimal preparation. But once your application is done, it is time to deploy the same on the server, you are stuck and you will seek help from your backend or DevOps mates.

Wait!! Being a front end guy it seems to be difficult, but depolying your application on server is relatively easier than writing state management in redux.

In this post, we will learn how to deploy a React application on an Ubuntu 18.04 server using Node.js, serve, and pm2

pm2 is a process manager for the JavaScript runtime Node.js. This is an open-source daemon process manager that helps to manage and keep application 24/7

Prerequisites

To follow this tutorial, you’ll need the following:

• Latest Node.js version installed on your computer or the Linux server where are you going to deploy the application.

  sudo apt-get update
  sudo apt-get install nodejs
  node -v or node –version
  npm -v or npm –version

• create-react-app tool

  npm install -g create-react-app

  Deploying the app

  1.First of all, create the app using npx create-react-app

    npx create-react-app my-app

  2.Now you can run the app by running following command in the project directory root

    npm start

  3.The default react app will run in http://localhost:3000

  4.Now install serve and pm2 packages globally on the system/server

  npm install -g serve
  npm install -g pm2

  5.Since you are in the root directory of your project, run the following command to create a production build of your app. This will create a directory named build in the project root directory

  npm run build 

  6.Now we can run the following command to deploy the app

    pm2 serve <path> <port> --spa

  In our case, we can run the following command

  pm2 serve build 8082 --spa 

  PM2 can serve static files very easily with the pm2 serve feature. It supports serving raw files from a specified folder or you can serve a SPA (Single Page Application) with it.

Now you can see that your application is running on 8081 port while you have logged out from your ssh terminal of the browser.

• Check the status of the application following command in the shell.

  pm2 list

Bonus: Below are some utility commands to manage the pm2 process

• Specify the app name pm2 --name <app-name>
• Delete all pm2 process pm2 delete all
• Delete specific process pm2 delete <app-name>
• Check the CPU and memory usage pm2 monit

Reference links :-

1. Quick start pm2
2. Process management with pm2

Source: Deploying a react app using pm2 and serve · LoginRadius Engineering