sdk/fidl/fuchsia.developer.bridge/mdns.fidl

// Copyright 2021 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/// A simple mDNS service for the daemon. Includes an API for subscribing to
/// events, as well as inspecting cached info.
///
/// Some more context on how targets are cached: when receiving an mDNS packet,
/// there is an additional record section that contains the nodename of the
/// target, its TTL (in seconds), and some additional metadata.
library fuchsia.developer.bridge;

/// Contains information about the socket bound during mDNS setup.
table MdnsBindEvent {
    1: uint16 port;
};

union MdnsEventType {
    /// Sent to subscribers when a new target is found on the network. This
    /// is only propagated when the target is either seen for the first time,
    /// or if the target has previously expired.
    1: Target target_found;
    /// Sent to subscribers when a target has been discovered after having
    /// alreaady been stored in the cache. This can often be treated the same
    /// as `target_found`.
    2: Target target_rediscovered;
    /// Sent to subscribers when a target has expired (the target has not been
    /// rediscovered after the TTL has been reached). The target can be
    /// rediscovered later. If this happens a `target_found` event will be sent.
    3: Target target_expired;
    /// An event propagated when the multicast listener is bound. Primarily
    /// for testing.
    4: MdnsBindEvent socket_bound;
};

[Discoverable]
protocol Mdns {
    /// Gets the next event from the protocol. There is only ever meant to be
    /// one event ready at a time on the service side, so it is important that
    /// the client call this frequently.
    GetNextEvent() -> (MdnsEventType? event);

    /// Gets full cache of targets. It is advised to call this before
    /// `GetNextEvent()`.
    GetTargets() -> (vector<Target>:512 targets);
};