Advanced · Module 8 · Lesson 2 of 11
Protocol-Independent Networking: getaddrinfo and Dual-Stack IPv4/IPv6
Build protocol-independent network software using getaddrinfo, traverse DNS resolution lists, resolve service ports, and deploy dual-stack IPv4/IPv6 sockets.
By the end you can
- Eliminate protocol hardcoding using getaddrinfo and freeaddrinfo
- Iterate through resolved addrinfo linked lists to establish resilient socket connections
- Perform reverse DNS lookups and format host/service strings using getnameinfo
- Configure dual-stack IPv6 sockets using IPV6_V6ONLY to service IPv4 and IPv6 clients simultaneously
Builds on Socket Foundations: Berkeley Sockets, Address Structures, and TCP Handshakes.
01 · A question first
Why does hardcoding AF_INET and struct sockaddr_in break on modern cellular and data-center IPv6-only networks, and how can a single listening socket accept connections from both IPv4 and IPv6 clients without running separate server processes?
Make a guess before you read on.
02 · The idea
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What's inside
- Start with the problem
- How the idea works
- Production Pattern: The Resilient Client Connection Loop
- Production Pattern: The Protocol-Independent Server
- Reverse Lookups: getnameinfo()
- Dual-Stack IPv6 Sockets
- Why it is correct
- What it costs
03 · Practice
Asked in interviews
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