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Intro To NodeJS: Session 4

Table of Contents

  1. Networks
  2. HTTP Protocol
  3. IP Address
  4. DNS (Domain Name System)
  5. APIs (Application Programming Interfaces)
  6. Express NodeJS - First API call
  7. API Testing
  8. References

What is a Network ?

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

Common Types of Networks:

  • Local Area Network (LAN)
  • Wid Area Network (WAN)

Network Layers

  • OSI Model
  • TCP/IP Model

HTTP Protocol

Explain the backbone of communication between clients and servers:

  1. What is HTTP ?

    • Hypertext Transfer Protocol: A stateless, application-layer protocol used for transferring data over the web.

  2. HTTP Methods

    • GET
    • POST
    • PUT
    • DELETE
    • PATCH

  3. HTTP Request/Response cycle.

    • Request: URL, Method, Headers, and Body.
    • Response: Status codes (e.g., 200 OK, 404 Not Found, 500 Internal Server Error), Headers, Body.

  4. HTTP Headers

    • Common headers: Content-Type, Authorization, Cache-Control, etc.

  5. HTTP VS HTTPS:

    • Secure communication with SSL/TLS.

  6. Cookies and Sessions

    • State management and authentication.

IP Address:

  1. What is an IP Address ?

    An IP address (Internet Protocol address) is a unique identifier assigned to devices on a network (like computers, phones, servers). It helps devices locate and communicate with each other over the internet or a private network.

  2. IPv4 VS IPv6:

    • IPv4 (Internet Protocol Version 4):
      • Format: IPv4 addresses are written in dot-decimal notation, consisting of four numbers separated by dots. Each number is between 0 and 255.
      • Example: 192.168.1.1
      • Bit Size: 32-bit address (2³² possible addresses, about 4.3 billion unique IPs).
      • Usage: Most common type of IP address, used since the early days of the internet.
      • Limitation: With the explosion of internet-connected devices, IPv4 addresses are running out, leading to the adoption of IPv6.
    • IPv6 (Internet Protocol Version 6):
      • Format: IPv6 addresses are written in colon-separated hexadecimal notation, consisting of eight groups of four hexadecimal digits.
        • Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
        • Groups of zeroes can be shortened with :: (e.g., 2001:db8::8a2e:370:7334).
      • Bit Size: 128-bit address (2¹²⁸ possible addresses, about 340 undecillion unique IPs).
      • Usage: Designed to replace IPv4 and accommodate the growing number of devices. It also improves security and efficiency.
Tables Are Cool
Address Size 32-bit (4.3 billion IPs) 128-bit (340 undecillion IPs)
Format Decimal (e.g., 192.168.1.1) Hexadecimal (e.g., 2001:db8::1)
Security No built-in encryption Built-in IPSec for security
Efficiency Simple, but limited Optimized for modern networks
Address Length Shorter Longer

DNS (Domain Name System)

Cover how DNS plays a role in resolving web addresses:

  1. What is DNS?
    • Converts human-readable domain names (e.g., example.com) into IP addresses.
  2. DNS Components:
    • Domain Name, IP Address, Nameservers.
  3. DNS Lookup Process:
    • Recursive Resolver → Root Server → TLD Server → Authoritative Name Server.
  4. Caching:
    • Role of DNS caching in speeding up requests.
  5. DNS Records:
    • A

      • Purpose: Maps a domain name.

      • Example: example.com A 192.168.1.1

      • Usage: Directs traffic to a server's IPv4 address.

    • AAAA

      • Purpose: Maps a domain name to an IPv6 address.

      • Example: example.com AAAA 2001:0db8:85a3::8a2e:0370:7334

      • Usage: Directs traffic to a server's IPv6 address.

    • CNAME

      • Purpose: Aliases one domain name to another.

      • Example: www.example.com CNAME example.com

      • Usage: Allows www.example.com to point to example.com without duplicating A or AAAA records.

    • MX
      • Purpose: Specifies the mail servers responsible for receiving emails for a domain.
      • Example: example.com MX 10 mail.example.com
        • Priority: Lower numbers have higher priority (e.g., 10 is higher priority than 20).
      • Usage: Routes emails to the correct mail server.
    • TXT
    • NS
    • SOA
    • PTR
    • SRV
    • ALIAS or ANAME Record
  6. Common DNS Issues:
    • DNS propagation delays, misconfigurations.

APIs (Application Programming Interfaces)

Discuss how backend systems communicate using APIs:

  1. What is an API?
    • Interface for communication between software components.
  2. Types of APIs:
    • REST (most common)
    • GraphQL
    • SOAP
    • gRPC.
  3. RESTful APIs:
    • Principles:
      • Stateless: means that calls can be made independently of one anther
      • CRUD Operations: Create, Read, Update, Delete.
      • Via HTTP protocol
    • JSON and XML formats.
  4. Authentication in APIs:
    • API keys, OAuth2, JWT.
  5. API Documentation:
    • Importance of clear docs and tools like Swagger, Postman,Thunder clint .

Express NodeJS - First API call

To establish a server using Node.js, you can use either the built-in http module or Express.js (which simplifies the process). Below are two methods:

  • Method 1 (Using Node.JS direct):
  const http = require('http');

  // Create a server
  const server = http.createServer();

  // Listen on a port
  const PORT = 3000;
  server.listen(PORT, () => {
      console.log(`Server running on http://localhost:${PORT}`);
  });
  • Method 2 (Using Express Node.JS)
  const express = require('express');
  const app = express();

  // Listen on a port
  const PORT = 3000;
  app.listen(PORT, () => {
      console.log(`Server running on http://localhost:${PORT}`);
  });

API Testing:

Task

  1. Make sure to understand all the previous sessions.
  2. Publish a server using Node.Js direct.
  3. Publish a server using Express.Node.Js.
  4. Access the server though your phone.
  5. Only run meefr-quiz-game test - follow the steps mentioned in readme file.

Task submission:

on github tasks repo.

References

Specific Refs:

Optional Refs: