Computer Networking Basics
Which correctly pairs protocols with the standard port numbers their servers use?
- AHTTP 80, HTTPS 443, DNS 53
- BHTTP 8080, HTTPS 443, DNS 25
- CHTTP 80, HTTPS 22, DNS 53
Show answer and explanation
Answer: A. HTTP 80, HTTPS 443, DNS 53
A port number is a 16-bit number from 0 to 65535 that identifies which application on a host, reached by IP address, the traffic is for. Ports 0–1023 are called well-known ports and are assigned to major services. Typical ones are HTTP 80, HTTPS 443, DNS 53, SSH 22 and SMTP (mail transfer) 25. The client side uses a number chosen by the OS each time (an ephemeral port) as its source port. Services can run on non-standard numbers; 8080 is often used for web development or proxy servers, but then the connecting side has to specify the number.
- A. Correct. HTTP is 80, HTTPS is 443 and DNS is 53.
- B. 8080 is a commonly used non-standard number, and 25 is the mail transfer (SMTP) port.
- C. 22 is the SSH port; HTTPS is 443.