| # Target Collection |
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| The daemon maintains discovered and connected targets that are accessible by the `TargetCollection` fidl protocol defined in `src/developer/ffx/fidl/target.fidl`. |
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| ## Daemon Events |
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| When a new target is discovered `DaemonEvent::NewTarget` is published to all daemon event listeners. This is currently used by the repository server to synchronize repos with a newly connected target once it establishes an RCS connection. |
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| When a target is updated, `DaemonEvent::UpdatedTarget` is published. This is currently unused. |
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| ## Target Events |
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| Each target has an event queue. |
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| `TargetEvent::RcsActivated` is published when an RCS connection is established. |
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| `TargetEvent::Rediscovered` is published when a target is updated. The name is a misnomer: while it fires when the target is discovered, it also fires when any target property is changed. |
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| `TargetEvent::SshHostPipeErr` is published when the Overnet Host Pipe (for RCS) hits an error. |
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| `TargetEvent::ConnectionStateChanged` is published when the connection state of a target is changed, and contains both the previous and current connection state. |
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| ## Discovery |
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| Discovery is handled outside of Target Collection, but is the primary way targets are added to it. The current discovery mediums are: mDNS, USB, and the emulator file watcher. |
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| mDNS discovery is both passive and active: It collects and parses mDNS packets but it also broadcasts mDNS requests. |
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| USB discovery is passive: Periodically it reenumerates USB devices and parses the operating system's cached USB descriptor. |
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| Emulator discovery is passive: It watches for changes to a directory `ffx emu` manages. |
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| ## Manual Targets |
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| Manual targets are pinned within the target collection and survive across daemon restarts. Consider it an alternative form of discovery that is sourced from the config. |
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| Manual targets are configured via `ffx target add` or `ffx config`. This is currently done by address only. |
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| ## Ephemeral Manual Targets |
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| Ephemeral Manual targets are manual targets that are allowed to expire after a period of time. Expiry happens once the target disconnects. |
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| Currently unused. |
