Split an IPv4 Address into Octets

Dotted-Quad Notation

An IPv4 address like 192.168.1.10 is just a 32-bit number displayed as four 8-bit octets. Every router, firewall rule, and socket API call works with the numeric form; the dotted string exists for humans. For example, 8.8.8.8 packs into four bytes: 08 08 08 08 in hex.

Parsing and Validation

The functions inet_aton and inet_pton in every C network program do exactly what you are about to do: split the string on dots, validate each part fits in 0-255, and pack the result. Common pitfalls include:

• Accepting octal notation like 010.0.0.1 (some parsers treat leading zeros as octal)
• Allowing values above 255 in a single octet
• Mishandling empty fields like 192..1.1

Get this wrong and you connect to the wrong host or accept malformed input, which has caused real CVEs in address parsers.

Why This Exercise

This task asks you to implement the first step of every network client: turn a human-readable address into four integers. You will need this same split-and-validate logic when you parse IP headers in later tasks and when you fill sockaddr_in structures by hand. The dotted string is a presentation format; the four integers are what bind(), routing tables, and firewall rules actually store.