Learning Objectives

By the end of this chapter, you should be able to:

• Explain what a network port is and why ports are necessary.
• Understand the relationship between IP addresses and port numbers.
• Differentiate between TCP and UDP.
• Classify port numbers into well-known, registered, and dynamic/private ranges.
• Identify common ports used in DevOps, cloud computing, databases, web servers, and Kubernetes.
• Understand how firewalls and security groups use ports.
• Apply port and protocol knowledge to real-world troubleshooting.

Introduction

Imagine a company headquarters with a single street address.

Every employee works in the same building, but each department has its own office number.

For example:

Company Address
25 Cloud Street

Reception → Office 100
Finance → Office 210
HR → Office 315
Engineering → Office 450

If someone sends a package to:

25 Cloud Street

the package still cannot be delivered until the office number is known.

Computers work the same way.

An IP address identifies the device.