← ACARA Digital Technologies Years 9–10

Port numbers

An IP address followed by a port number. The IP finds the device and the port (80 = HTTP) tells it which service gets the data. Others: 443 HTTPS, 25 SMTP, 53 DNS.

Part of: ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 54, WA Computer Science ATAR Year 11 — Network Communications — Module 54, WA Computer Science ATAR Year 11 — Cyber Security — Module 23

Understanding Port numbers in ACARA Digital Technologies Years 9–10

What it does: The IP address 192.168.1.10 finds the device. Port 80 tells it to hand the data to its HTTP web service, not to a different service on the same device. HTTP uses port 80. Port 443 is for HTTPS, the secure version. Port 25 is for SMTP, which sends email. Web pages over HTTP use port 80. A colon separates the IP address from the port number. A full stop would make it look like part of the IP address.

Common mistakes: HTTP uses port 80. Port 443 is for HTTPS. The line should be HTTP: 192.168.1.10:80. Email sent with SMTP uses port 25. Port 53 belongs to DNS. The line should be Mail: 192.168.1.20:25.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Port numbers to a class →

This module's key terms are also in a printable crossword (Modules 41–55) and word search (Modules 12–55).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
In 192.168.1.10:80, what does the number after the colon tell the receiving device?
Which program or service the data is forWhich device on the network should get the data
Matches
192.168.1.10.80
↓
The port is joined with a dot instead of a colon. It reads like a five-part address, so the device cannot tell which service is wanted. It should be 192.168.1.10:80.
Applying
Meanings
Term
192.168.1.10:80
Meaning
An IP address followed by a port number. The IP finds the device and the port (80 = HTTP) tells it which service gets the data. Others: 443 HTTPS, 25 SMTP, 53 DNS.
Practice
192.168.1.10:80 HTTP
Testing
Gaps
192.168.1.10:
Check Answer
Spots
1HTTP: 192.168.1.10:443
2HTTPS: 192.168.1.10:443

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

The 'Nautilus' badge — Default Expert, one of Cloodit's 106 collectible badges
Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy
Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games
Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print
Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. In 192.168.1.10:80, what does the number after the colon tell the receiving device?
A. Which device on the network should get the data
B. Which program or service the data is for ✓
The IP address finds the device. The port number after the colon picks the service on that device.
2. Which port number is normally used for HTTP web traffic?
A. 80 ✓
B. 443
HTTP uses port 80. Port 443 is for HTTPS, the secure version.
3. Which port number is normally used for HTTPS?
A. 25
B. 443 ✓
HTTPS uses port 443. Port 25 is used by SMTP for sending email.
4. A server at 10.0.0.5 runs a web server and a mail server. How do they share one IP address?
A. Each service listens on its own port number ✓
B. Each service needs its own IP address
One IP address can offer many services at once because each one uses a different port, such as 10.0.0.5:80 and 10.0.0.5:25.
5. Which port number does the DNS service normally use?
A. 53 ✓
B. 80
DNS uses port 53 to turn domain names into IP addresses. Port 80 is for HTTP.

Match the Pairs

192.168.1.10:443 → Send data to the device at 192.168.1.10, for its HTTPS (secure web) service
192.168.1.10:25 → Send data to the device at 192.168.1.10, for its SMTP (sending email) service
One device can run several services at once. The port number picks which service gets the data → 192.168.1.10:80
A DNS server is reached by using the DNS port number after its IP address → 192.168.1.1:53
192.168.1.10.80 → The port is joined with a dot instead of a colon. It reads like a five-part address, so the device cannot tell which service is wanted. It should be 192.168.1.10:80.
192.168.1.10:25 for a secure web page → Port 25 is for SMTP email, not web pages. A secure web page uses HTTPS on port 443, so it should be 192.168.1.10:443.

Key Term

192.168.1.10:80
An IP address followed by a port number. The IP finds the device and the port (80 = HTTP) tells it which service gets the data. Others: 443 HTTPS, 25 SMTP, 53 DNS.

Fill in the Blanks

1. 192.168.1.10:80
Hint: Type the port number that web servers use for plain HTTP.
2. 192.168.1.10:80 192.168.1.10:443
Hint: Same device, second service. Type the port number used for secure web traffic (HTTPS).
3. 192.168.1.20:25
Hint: Type the port number a mail server uses to receive sent email (SMTP).
4. 8.8.8.8:53
Hint: Type the port number used by the DNS service to look up domain names.
5. 192.168.1.10:80
Hint: Type the single character that separates the IP address from the port number.

Spot the Error

Question 1
A HTTP: 192.168.1.10:443
B HTTPS: 192.168.1.10:443
C SMTP: 192.168.1.10:25
Line A — HTTP uses port 80. Port 443 is for HTTPS. The line should be HTTP: 192.168.1.10:80.
Question 2
A DNS: 192.168.1.20:53
B Web: 192.168.1.20:80
C Mail: 192.168.1.20:53
Line C — Email sent with SMTP uses port 25. Port 53 belongs to DNS. The line should be Mail: 192.168.1.20:25.
Question 3
A url = https://shop.com
B port = 80
C send to 192.168.1.10:port
Line B — An https:// address is sent to port 443, because port 80 is plain HTTP. The line should be port = 443.
Question 4
A address = 192.168.1.10;80
B service = HTTP
C send(address, data)
Line A — A port number is written after the IP address with a colon, not a semicolon. It should be 192.168.1.10:80.
Question 5
A query = lookup(shop.com)
B send query to 192.168.1.1:25
C print(reply)
Line B — DNS queries go to port 53. Port 25 is for SMTP email. The line should end in :53.

Student with a class code? Join your class →