mgth/LittleBigMouse · error · InvalidOperationException

Could not find the network interface used to reach

Error message

Could not find the network interface used to reach {remoteAddress}.

What it means

ControllerMacFor connects a UDP socket to the projector's MQTT port to learn which local endpoint the OS would route through, then scans all network interfaces for one owning that local IP. If no interface's unicast addresses match the socket's local endpoint, it throws this InvalidOperationException. This indicates the routing/table snapshot was inconsistent or the interface disappeared.

Solutions

1. Verify the machine still has an active network interface with a route to the projector's subnet, then retry.
2. Check the projector's IP is on a reachable subnet (ping it) and reconnect Wi-Fi/Ethernet if it dropped.
3. Disable/re-enable or reset the VPN or virtual adapters if routing is being rewritten.
4. Retry after a short delay — transient interface flaps usually resolve; add a fallback that re-resolves on next attempt.

Example fix

// before
var mac = NetworkIdentity.ControllerMacFor(projectorIp); // throws if route/interface flapped

// after
string mac;
try { mac = NetworkIdentity.ControllerMacFor(projectorIp); }
catch (InvalidOperationException)
{
    await Task.Delay(500);
    mac = NetworkIdentity.ControllerMacFor(projectorIp); // retry after interface settles
}

bool routeReachable = System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable() &&
    new Ping().Send(projectorIp, 1000).Status == IPStatus.Success;

try
{
    var mac = NetworkIdentity.ControllerMacFor(remoteAddress);
}
catch (InvalidOperationException ex) when (ex.Message.StartsWith("Could not find the network interface"))
{
    // wait for interface/route to settle, retry once, then surface connectivity guidance
}

When it happens

Trigger: Calling ControllerMacFor when the local interface used to route to remoteAddress vanished or changed between socket.Connect and the NetworkInterface enumeration: Wi-Fi disconnect, VPN tunnel drop, interface flapping, virtual adapter removal, or unusual routing (e.g. address returned not bound to any listed unicast address).

Common situations: Laptop switched from Wi-Fi to Ethernet mid-operation; VPN client rewriting routes; Hyper-V/WSL/vEthernet virtual adapters confusing enumeration; sleep/resume leaving stale interface state; projector on a subnet whose route was removed.

Related errors

• No VIDAA descriptor answered at
• No Hisense VIDAA device answered on
• Enter the projector Wi-Fi MAC address first.
• Associate a Hisense VIDAA projector first.
• Enter a valid projector IPv4 address.

AI-assisted analysis of mgth/LittleBigMouse@7a42f01d47 (2026-09-16). Data as JSON: /api/errors/c7b16e7c3b6b2b10. Report an issue: GitHub.

Appendix: source

Thrown at LittleBigMouse.Plugins/LittleBigMouse.Plugin.Vcp.Avalonia/HisenseVidaa/NetworkIdentity.cs:24

namespace LittleBigMouse.Plugin.Vcp.Avalonia.HisenseVidaa;

static class NetworkIdentity
{
    public static string ControllerMacFor(string remoteAddress)
    {
        if (!Ipv4Address.TryParse(remoteAddress, out var remote))
            throw new ArgumentException("Enter a valid projector IPv4 address.", nameof(remoteAddress));

        using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        socket.Connect(new IPEndPoint(remote, HisenseVidaaProtocol.MqttPort));
        var local = ((IPEndPoint)socket.LocalEndPoint!).Address;
        foreach (var network in NetworkInterface.GetAllNetworkInterfaces())
        foreach (var address in network.GetIPProperties().UnicastAddresses)
            if (address.Address.Equals(local))
                return HisenseVidaaProtocol.NormalizeMac(network.GetPhysicalAddress().ToString());

        throw new InvalidOperationException($"Could not find the network interface used to reach {remoteAddress}.");
    }
}

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