# discovery_cli

A development tool for testing the discovery layer. Announces a node on the local network via UDP multicast and prints peers as they appear and disappear.

---

## Build

From the repository root:

```sh
make cli
```

The binary is placed in `build/cli/`.

---

## Usage

```sh
discovery_cli <name> <tcp_port> [flags]
```

| Argument | Description |
|---|---|
| `name` | Node name in `namespace:instance` form, e.g. `v4l2:microscope` |
| `tcp_port` | The TCP port this node listens on for transport connections |
| `flags` | Comma-separated role list: `source`, `relay`, `sink`, `controller` (default: `source`) |

Example — announce a source node and watch for peers:

```sh
./discovery_cli camera:0 8000 source
```

Example output as peers are found and lost:

```
found: unnamed:0  192.168.1.42:8001  site=0  flags=source
found: display:0  192.168.1.55:8002  site=0  flags=sink
lost:  unnamed:0  192.168.1.42:8001
```

Run two instances on the same machine (different ports) to verify mutual discovery.

---

## Relationship to the Video Routing System

`discovery_cli` exercises the `discovery` module, which the video node uses to find peers on the LAN without configuration. The node starts a discovery listener on startup; controllers use discovered peer tables to locate nodes before connecting.

See also: [`query_cli.md`](query_cli.md) for a combined discovery + protocol query.