🚪 Common Networking Ports & Protocols

📌 Overview

A Port is a logical communication endpoint that identifies a specific process or service on a computer.

Analogy: If the IP Address is the "Building Address", the Port Number is the "Apartment Number" or "Office Number" inside that building.
Range: 0 to 65535.

🔢 Port Categories

Range	Name	Description	Example
0 - 1023	Well-Known Ports	Reserved for core system services.	HTTP (80), SSH (22)
1024 - 49151	Registered Ports	Used by user applications & vendor services.	SQL (1433), RDP (3389)
49152 - 65535	Dynamic Ports	Temporary ports for client-side outgoing connections.	Browser tabs

📜 Detailed Port Guide

1. File Transfer & Remote Access

Port	Protocol	Name	Description	Azure Context
20/21	TCP	FTP	File Transfer Protocol. Unencrypted.	Used for older App Service uploads. Avoid if possible (Use SFTP).
22	TCP	SSH	Secure Shell. Encrypted Command Line.	Critical for managing Linux VMs.
23	TCP	Telnet	Unencrypted Remote CLI.	Blocked/Avoid. Never use in Cloud.
3389	TCP	RDP	Remote Desktop Protocol. GUI Access.	Critical for managing Windows VMs.

2. Web & Email

Port	Protocol	Name	Description	Azure Context
80	TCP	HTTP	Unsecured Web Traffic.	Standard web hosting.
443	TCP	HTTPS	Secured (SSL/TLS) Web Traffic.	Mandatory for secure Azure Web Apps.
25	TCP	SMTP	Simple Mail Transfer Protocol.	Sending email. Blocked by default in Azure to prevent spam.
110	TCP	POP3	Post Office Protocol v3.	Receiving email (Downloads locally).
143	TCP	IMAP	Internet Message Access Protocol.	Receiving email (Synced on server).

3. Infrastructure & Database

Port	Protocol	Name	Description	Azure Context
53	UDP/TCP	DNS	Domain Name System.	Resolves names to IPs. Azure DNS uses this.
67/68	UDP	DHCP	Auto-assigns IP addresses.	Managed automatically by Azure VNet.
1433	TCP	SQL	MSSQL Server Default Port.	Connecting to Azure SQL Database.
3306	TCP	MySQL	MySQL Database Port.	Connecting to Azure Database for MySQL.
5432	TCP	PostgreSQL	PostgreSQL Database Port.	Connecting to Azure Database for PostgreSQL.

🖼️ Architecture Diagram (The "Apartment" Analogy)

       [  Server IP: 10.0.0.5  ]
      +-------------------------+
      |                         |
      |   [ Port 80 ]  <-- (Building Entry for Web Requests)
      |       |
      |   (Web Server App)      |
      |                         |
      |-------------------------|
      |                         |
      |   [ Port 22 ]  <-- (Service Entry for Admin/Maintenance)
      |       |
      |   (SSH Service)         |
      |                         |
      +-------------------------+

💡 Hinglish Explanation (Office Building)

1. Port (Cabin Number)

Hinglish: Imagine karo ek badi Office Building (Server) hai.
IP Address: Building ka address hai.
Port: Building ke andar alag-alag Cabins hain.
- Cabin 80 (Reception): Yahan public aati hai (Web Private).
- Cabin 22 (Security Room): Yahan sirf Admin access kar sakta hai (SSH).
- Cabin 1433 (Store Room): Yahan files/data rakha hai (SQL).

2. Open vs Closed Ports

Hinglish: Agar Cabin 80 ka darwaza band hai (Port Closed), toh koi andar nahi aa sakta, chahe wo Building tak pahunch jaye. Firewall ka kaam yahi darwaze kholna ya band karna hai.

⚡ Exam Tips for AZ-900

NSG Rules: You must explicitly Allow ports in Network Security Groups (NSGs) for traffic to flow.
- Example: To host a website, allow Port 80/443.
- Example: To admin a VM, allow Port 22 (Linux) or 3389 (Windows).
Security: Keep management ports (22, 3389) closed to the public internet using JIT (Just-In-Time) Access or Bastion.
SMB (Port 445): Used for Azure Files storage mounting. often blocked by ISPs.