Cybersecurity Foundations · 4 min
Ports
How one address hosts many services
This lesson explains the concept, then checks your understanding in a short interactive exercise.
A port is a numbered doorway
A port is a number (0-65535) that identifies a specific service or connection on a device. The IP address gets data to the right machine; the port gets it to the right program on that machine.
- IP address: which device
- Port: which service on that device
- A device can have many ports active at once
Common ports are conventions
Some port numbers are widely associated with certain services by convention, not by law:
- 22 — often SSH (remote login)
- 53 — often DNS
- 80 — often HTTP
- 443 — often HTTPS
- 3389 — often RDP (remote desktop)
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