Question 1

What is a port number?

Accepted Answer

A port number is a 16-bit unsigned integer (0–65535) that identifies a specific process or network service on a host. Ports allow multiple services to run on a single IP address by directing traffic to the correct application.

Question 2

What is the difference between TCP and UDP?

Accepted Answer

TCP (Transmission Control Protocol) is connection-oriented and guarantees reliable, ordered delivery of data. UDP (User Datagram Protocol) is connectionless and faster but does not guarantee delivery or order, making it suitable for streaming and real-time applications.

Question 3

What are well-known ports?

Accepted Answer

Well-known ports range from 0 to 1023 and are assigned by IANA to common services. For example, HTTP uses port 80, HTTPS uses port 443, SSH uses port 22, and FTP uses port 21.

Question 4

How many port numbers are there?

Accepted Answer

There are 65,536 port numbers (0–65535), divided into three ranges: well-known ports (0–1023), registered ports (1024–49151), and dynamic/private ports (49152–65535).

Question 5

Can a port be used by both TCP and UDP?

Accepted Answer

Yes. TCP and UDP port number spaces are independent. A service can listen on the same port number for both protocols. For example, DNS uses port 53 for both TCP and UDP.

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