Common Service Ports (80, 443, 22, 25, 53)

The Ports You'll Encounter Constantly

Why 80 and 443 Coexist

Port 80 (plain HTTP) still exists largely to support older links and to redirect visitors to the encrypted HTTPS version on port 443 - modern websites almost universally prefer 443 for actual content delivery, using 80 mainly as a redirect stepping stone rather than for serving real traffic.

Why Port 22 (SSH) Matters So Much for Administrators

SSH is the standard way system administrators securely log into and manage remote servers - port 22 being publicly exposed on a server is extremely common, which also makes it a frequent target for automated password-guessing attacks, reinforcing why strong authentication matters (as covered in the security best practices note).

A Nuance: SMTP's Port 25 vs Port 587

While port 25 is SMTP's traditional well-known port, many mail providers today use port 587 (with authentication and encryption) specifically for mail submission from user email clients, reserving port 25 mainly for server-to-server mail delivery.

Why Understanding These Beats Pure Memorization

These five ports show up constantly in networking, security, and web development - recognizing them on sight, and understanding why each service uses its specific port, is far more useful in practice than simply memorizing a disconnected list of numbers.