Layer: Foundation · Build flags: PROTOCORE_ENABLE_IPV6

What this example teaches

The server is already dual-stack: the TCP and UDP listeners bind IPADDR_TYPE_ANY, so the moment the interface has an IPv6 address it answers over v6 as well as v4. All you add is turning IPv6 on for the network interface:

Physical.wifi->init(SSID, PASSWORD);
while (!Physical.wifi->ready()) delay(250);
Physical.ip6->init();            // enable IPv6 (SLAAC) on the Wi-Fi netif
while (!Physical.ip6->ready()) delay(250); // waits for a global (routable) v6 address

PROTOCORE_ENABLE_IPV6 gates the bring-up. Physical.ip6->init() enables IPv6 on the netif (SLAAC gives a fe80:: link-local address, plus a global one if a router advertises a prefix). Physical.ip6->global_addr() reads the acquired global address straight from lwIP into a protocore_ip.

The protocore_ip address core

network_drivers/network/ip.h is one family-tagged type for both v4 and v6, with:

**protocore_ip_parse()** - RFC 4291 text (dotted-quad; v6 with :: zero-compression and the embedded-v4 ::ffff:a.b.c.d tail).
**Ip.format()** - the RFC 5952 canonical form (lower-case, no leading zeros, longest zero run compressed, v4-mapped shown dotted).
**Ip.classify()** - loopback / link-local / private-ULA / multicast / global.

It is pure and host-tested (pio test -e native_ip), so the address handling is verified off-device; the netif bring-up is ESP32-only.

Try it

Flash, open Serial @ 115200 for the addresses, then (note the brackets and curl -g):

curl -g "http://[2001:db8::abcd]/" # your printed global address

Build-flag note

The flag must reach the whole library build:

pio ci --board=esp32dev --project-option="framework=arduino" \
  --project-option="build_flags=-DPROTOCORE_ENABLE_IPV6=1" \
  --lib="." examples/Foundation/IPv6/IPv6.ino

Requires an lwIP built with LWIP_IPV6=1 (the stock Arduino-ESP32 core ships it). In the Arduino IDE the build_opt.h beside this sketch sets the flag for you.