I’m implementing LAN peer discovery in Rust using UDP broadcast (Tokio).

Setup

• Windows + Fedora Linux
• Same Wi-Fi network
• UDP port 7777
• tokio::net::UdpSocket

Issue

• Linux can discover Windows
• Windows cannot discover Linux
  So discovery only works one way.

Broadcast sender:

let socket = UdpSocket::bind("0.0.0.0:0").await?;
socket.set_broadcast(true)?;
socket.send_to(b"COPYD_DISCOVER", "255.255.255.255:7777").await?;

Listener:

let socket = UdpSocket::bind("0.0.0.0:7777").await?;
socket.set_broadcast(true)?;

let (size, addr) = socket.recv_from(&mut buffer).await?;
if &buffer[..size] == b"COPYD_DISCOVER" {
    socket.send_to(b"COPYD_PEER", addr).await?;
}

Checks done

• Windows Defender firewall allows UDP
• Fedora firewall allows UDP 7777
• No VPN, same subnet

Questions

1. Is 255.255.255.255 unreliable for Windows → Linux discovery?
2. Should I send subnet-directed broadcasts (e.g. 192.168.x.255) instead?
3. Are there OS differences in handling UDP broadcast with Tokio?
4. What’s the recommended cross-platform LAN discovery pattern in Rust?

Any guidance from people who’ve done cross-platform UDP discovery would help a lot. Thanks!

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