DDNS Client using Node and Typescript

Project Description

Build an DDNS client using Object Oriented Programming and Async code that:

• Checks the status of a web page.
• If it’s down check that the DNS record matches the external IP of the server.
• If not then update the DNS Provider with an HTTP Get request.
• User can add more than one site.
• The program will loop through each site on an interval set by the user.
• The client will be able to make updates to freedns.afraid.org

Project Dependencies

Linux or Windows system running on the same web server, or network that share the external IP of the web server. Since node runs on either, the client will help keep your up-time for either kind of server.

Node.js The app will be written entirely in node. A back-end language built on Chrome’s V8 engine. version: 12.16.3 LTS.

Typescript (optional) If you opt-out of TypeScript, the assumption is that you know enough Node.js that you can figure out how/what to write based on the typescript. version 6.14.5

Planning

First we will list the separate responsibilities and use this plan to maintain Single Responsibility Principle

• Interval Polling of site analysis.
• Configuration of website information.
• Checking site availability.
• Checking DNS.
• Updating DNS using HTTP Request.
• Logging of Errors.

Initialization

Create a folder for the project. I will use C:/git/ddns-client but you can use anything you like.

Run the following commands in the terminal.

PS C:\git\ddns-client> npm init

We’ll start with an npm init to generate our package.json. If this is your first time, accept defaults. You’ll learn the rest along the way. Add a start script below. the package.json file contains the meta information about your project, the dependencies, and the start, build or test scripts that you define.

  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node dist/index.js"
  },

PS C:\git\ddns-client> tsc --init

We’ll then use tsc init to generate our tsconfig.json. we’ll make the following changes to the tsconfig.json file.

"target": "ES2017",
"outDir": "./dist",
"resolveJsonModule": true,
//"strict": true,        /* We'll take advantage of typescript, but not to this extreme */  

TypeScript doesn’t ship with the knowledge of every possible import or language. This is on purpose to prevent projects from becoming too large with unused imports. run npm install @types/node -save-dev.

PS C:\git\ddns-client> npm install @types/node -save-dev

The -save-dev adds the dependency to the development dependency portion of the package.json.

How to transpile and run

Run tsc to transpile the TypeScript code into JavaScript and then run the app by running npm start.

PS C:\git\ddns-client> tsc
PS C:\git\ddns-client> npm start

Alternatively, open two terminals and run tsc -watch to automatically transpile every time you save. In another terminal run npm start when needed to start the app.

Terminal 1: 
PS C:\git\ddns-client> tsc -watch

Terminal 2:
PS C:\git\ddns-client> npm start

The Code

Create a fairly empty index.ts file. If you like, add a console.log(“Hello World”) to validate your setup.

We’ll next need to create our classes that will be used throughout the app.

Take note of how the Object.assign(this, initializer) is used in the constructor. For more explanation see Object.assign with this (Javascript). This will later allow us to map the JSON sites into our Site classes with minimal code.

Make an HTTP class. If you use any of the imports out there, find one that uses Promises. We’ll need that in our Async code later. Please examine the following code and comments.

We’ll also need something to check if the DNS is working okay. Not going to re-invent the wheel here. This is basic DNS lookup wrapped in a promise.

Before we can dive in, you need a working site. Define this information in a sites.json file. Modify the Hostname TestURL and Endpoint (username, password and hostname param) properties for your site.

Next we’re going to work on the logic piece. Examine the following code and comments.

No we’ll update the index.ts to start the application.

You can now run the app with npm start and run this through boot scripts or task scheduler.

Please comment below what should be added next to this project, Here are some things that can be added:

• Save Error logs to JSON file.
• Move configurable variables to config.json
• REST endpoint to see status of sites with Express
• Ability to sent HTTP Post requests.
• Separate sites from DNS Provider.

Complete Code

Github Repository: https://github.com/rimendoz86/ddns-slim