IP addresses and ports

What is an IP address?

An IP address identifies an interface on an IP network so devices can communicate. The two versions introduced here are IPv4 and IPv6.

IPv4 uses 32 bits, or four bytes. Its usual notation separates four 8-bit groups with dots. Converting each group from binary into decimal gives the familiar address format:

11000000.10101000.00000001.00100001 → 192.168.1.33

IPv6 was developed in part to address IPv4 address exhaustion. It uses 128 bits and is written in hexadecimal. Its full form contains eight 16-bit groups separated by colons, with leading zeros often omitted:

2000:1034:ab:2000:3:15:115:20

What is a port?

In networking software, a port identifies a logical endpoint used by a service or process. The word is also used for physical hardware connectors, but that is a different meaning.

An easy introductory distinction is: the IP address helps find the network endpoint, while the port helps identify the service at that endpoint.

TCP and UDP port numbers range from 0 to 65,535. The original article linked a list of TCP/UDP ports for examples of commonly assigned services.

Translation note: the source's upper bound of 65,536 was one too high; it is corrected above.

The next lesson introduces subnet masks.