# The serve command

The serve command is used to preview a book by serving it over HTTP at
`localhost:3000` by default. Additionally it watches the book's directory for
changes, rebuilding the book and refreshing clients for each change. A websocket
connection is used to trigger the client-side refresh.

#### Specify a directory

The `serve` command can take a directory as an argument to use as the book's
root instead of the current working directory.

```bash
mdbook serve path/to/book
```

#### Server options

`serve` has four options: the HTTP port, the WebSocket port, the HTTP hostname
to listen on, and the hostname for the browser to connect to for WebSockets.

For example: suppose you have an nginx server for SSL termination which has a
public address of 192.168.1.100 on port 80 and proxied that to 127.0.0.1 on port
8000\. To run use the nginx proxy do:

```bash
mdbook serve path/to/book -p 8000 -n 127.0.0.1 --websocket-hostname 192.168.1.100
```

If you were to want live reloading for this you would need to proxy the
websocket calls through nginx as well from `192.168.1.100:<WS_PORT>` to
`127.0.0.1:<WS_PORT>`. The `-w` flag allows for the websocket port to be
configured.

#### --open

When you use the `--open` (`-o`) flag, mdbook will open the book in your your
default web browser after starting the server.

#### --dest-dir

The `--dest-dir` (`-d`) option allows you to change the output directory for the
book. If not specified it will default to the value of the `build.build-dir` key
in `book.toml`, or to `./book` relative to the book's root directory.

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***Note:*** *The `serve` command is for testing, and is not intended to be a
complete HTTP server for a website.*