feat(examples): allow selecting the multicast interface#2
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The send_multicast and receive_reassemble examples hardcoded INADDR_ANY, so on Windows a Wi-Fi interface is often not selected by default and PONK multicast never crosses the WLAN. Both examples now take an optional local interface IPv4 address: the sender binds to it to pin egress, the receiver joins the group on it. Omitting the address preserves the previous all-interfaces behavior; an unparseable address warns and falls back. Interface selection stays an application-level policy in the examples, keeping the codec socket-agnostic and unsafe-free. Ports the intent of madmappersoftware/Ponk#16 to this Rust crate's I/O-owning layer.
A typo in the interface argument silently reverted to INADDR_ANY — the exact default-selection behavior the argument exists to override — so the example looked broken over WLAN rather than reporting the typo. An invalid address is now a hard error; a missing argument still defaults to all interfaces. Also scope the sender's bind() comment: it reliably steers multicast egress on Windows, but binding a unicast source address is not IP_MULTICAST_IF and is only a hint on other platforms.
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Summary
Ports the intent of upstream madmappersoftware/Ponk#16 ("Add network interface selection for multicast send/receive") to this Rust crate.
Both multicast examples hard-coded
INADDR_ANY, so on Windows a Wi-Fi interface is often not selected by default and PONK multicast never crosses the WLAN. Both examples now take an optional local interface IPv4 address:receive_reassemblejoins the group on the chosen interface (join_multicast_v4(&group, &interface)).send_multicastbinds to the interface address to steer egress.Omitting the argument preserves the previous all-interfaces behavior; an invalid address is a hard error rather than a silent revert to the default.
Scope: why this lives in the examples, not the library
This crate is a zero-dependency,
#![forbid(unsafe_code)]codec/reassembler where socket ownership and I/O deliberately remain with the application. The upstream PR's interface enumeration (getifaddrs/GetAdaptersAddresses) andIP_MULTICAST_IFboth require unsafe OS calls, so they are intentionally kept out of the library. The examples are the crate's I/O-owning layer and exhibit the exact Windows/WLAN failure the upstream PR fixes, so interface selection is applied there as an application-level policy.stdhas noIP_MULTICAST_IF, so the sender binds to the interface address — reliable on Windows, documented as a hint on other platforms.Usage
Testing
cargo fmt --all --checkcleancargo clippy --examples -- -D warningsclean