Ports and Protocols

Question 1

What is a protocol in networking?

Answer 1

A protocol is a standardized set of rules that define how data is formatted, transmitted, and processed across a network. It ensures devices can communicate clearly.

• Protocol = language (two devices can only talk if they speak the same one)

Question 2

What is a port and why is it important?

Answer 2

A port is a virtual number that directs traffic to the right app or service on a device. It helps manage multiple types of communication at once.

• Port = apartment number (same address, but different rooms for different services)

Question 3

What are the three standardized port ranges and their functions?

Answer 3

• 0–1023: Well‑known ports (company lines)
• 1024–49151: Registered ports (small business numbers)
• 49152–65535: Dynamic/private ports (burner phones for quick calls)

Question 4

What’s the difference between Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), and when should you use each?

Answer 4

• TCP (Transmission Control Protocol): Connection‑based, reliable, checks delivery — use for email, websites, file transfers
• UDP (User Datagram Protocol): Connectionless, fast, no delivery check — use for streaming, gaming, VoIP
• TCP = certified mail (tracked, secure)
• UDP = flyer tossed over a fence (quick, no guarantee)

Question 5

List the main email protocols and their port numbers.

Answer 5

• SMTP (Simple Mail Transfer Protocol – sending mail): 25
• IMAP (Internet Message Access Protocol – sync mail): 143
• POP3 (Post Office Protocol version 3 – download mail): 110

Question 6

List the main web protocols and their port numbers.

Answer 6

• ## HTTP (HyperText Transfer Protocol – postcard, anyone can read it): 80HTTPS (HyperText Transfer Protocol Secure – sealed envelope, private): 443

Question 7

List the main file transfer protocols and their port numbers.

Answer 7

• FTP (File Transfer Protocol – shipping with tracking): 20, 21
• TFTP (Trivial File Transfer Protocol – quick handoff, no security): 69

Question 8

List the main remote access protocols and their port numbers.

Answer 8

• Telnet (Telecommunication Network – public walkie‑talkie): 23
• SSH (Secure Shell – encrypted phone line): 22
• RDP (Remote Desktop Protocol – remote robot control of a PC): 3389

Question 9

List the main network services protocols and their port numbers.

Answer 9

• DNS (Domain Name System – phone book): 53
• NETBIOS (Network Basic Input/Output System – old‑school internal hallway system): 137–139
• DHCP (Dynamic Host Configuration Protocol – seat assigner): 67, 68
• SNMP (Simple Network Management Protocol – building monitor): 161, 162
• LDAP (Lightweight Directory Access Protocol – office directory): 389
• SMB (Server Message Block – shared folder room): 445

Question 10

What’s the relationship between ports and protocols in networking?

Answer 10

Protocols define how communication happens; ports define where it goes. Ports link data to the correct app using the appropriate protocol.

• Protocol = delivery method (mail, FedEx)
• Port = apartment number (where the delivery lands)

Question 11

How do port numbers, services, and applications work together?

Answer 11

Applications use protocols to send data, services listen on specific ports, and ports route the traffic to the right app.

• ## Example: Gmail (app) uses SMTP (protocol) through port 25 to send an emailAnalogy: Like a delivery app using the right doorbell in a huge apartment building