# Neon CLI command: dev

Run Neon Functions locally with a dev server

The `dev` command runs [Neon Functions](/guides/neon-functions-index) locally with a dev server and hot reload. Serve one function from its entry module, or every function declared in your `neon.ts` policy.

## Usage

```bash
neon dev [--source <path>] [options]
```

## Options

| Option     | Description                                                                                                                                                | Type   | Default | Required |
| ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------ | ------- | :------: |
| `--port`   | Port to listen on (single-function mode only, with --source). Fails if taken. Without it (and without a PORT env var) a free port is chosen automatically. | number | —       |    No    |
| `--source` | Path to a single function entry module. Omit to serve every function declared in neon.ts.                                                                  | string | —       |    No    |

## Examples

Serve one function on a free port with hot reload:

```bash
neon dev --source ./functions/hello.ts
```

Serve every function declared in `neon.ts` (one dev server each):

```bash
neon dev
```

Serve one function on an explicit port (fails if the port is taken):

```bash
neon dev --source ./functions/hello.ts --port 3000
```

## WebSockets

`neon dev` serves WebSocket upgrades locally, so you can test real-time functions before you deploy. Connect a client to the dev server's `ws://localhost:<port>` URL. See [WebSockets and SSE](/guides/neon-functions-websockets) for the function-side code.

## Related pages

- [Neon CLI command: config](./apis-sdks-cli-config.md)
- [Neon CLI command: deploy](./apis-sdks-cli-deploy.md)
- [Neon CLI command: status](./apis-sdks-cli-status.md)

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