```

////

The files and form fields will be uploaded as form data and you will receive the files and form fields.

And you can declare some of the files as `bytes` and some as `UploadFile`.

/// warning

        @functools.wraps(app)
        async def wrapped_app(scope, receive, send):
            if scope["type"] != "websocket":
                return await app(scope, receive, send)  # pragma: no cover

            async def call_next():
                return await app(scope, receive, send)

            websocket = WebSocket(scope, receive=receive, send=send)
            return await middleware_func(websocket, call_next)

If the client requests `http://example.com/items/foo` (an `item_id` `"foo"`), that client will receive an HTTP status code of 200, and a JSON response of:

```JSON
{
  "item": "The Foo Wrestlers"
}
```

But if the client requests `http://example.com/items/bar` (a non-existent `item_id` `"bar"`), that client will receive an HTTP status code of 404 (the "not found" error), and a JSON response of:

```JSON
{

```Python hl_lines="10"
{!> ../../docs_src/header_param_models/tutorial002.py!}
```

////

If a client tries to send some **extra headers**, they will receive an **error** response.

For example, if the client tries to send a `tool` header with a value of `plumbus`, they will receive an **error** response telling them that the header parameter `tool` is not allowed:

```json
{
    "detail": [
        {

```

////

If a client tries to send some **extra** data in the **query parameters**, they will receive an **error** response.

For example, if the client tries to send a `tool` query parameter with a value of `plumbus`, like:

```http
https://example.com/items/?limit=10&tool=plumbus
```

They will receive an **error** response telling them that the query parameter `tool` is not allowed:

```json
{

A `Request` also has a `request.receive`, that's a function to "receive" the body of the request.

The `scope` `dict` and `receive` function are both part of the ASGI specification.

And those two things, `scope` and `receive`, are what is needed to create a new `Request` instance.

///

## Await for messages and send messages

In your WebSocket route you can `await` for messages and send messages.

```Python hl_lines="48-52"
{!../../docs_src/websockets/tutorial001.py!}
```

You can receive and send binary, text, and JSON data.

## Try it

If your file is named `main.py`, run your application with:

<div class="termy">

```console
$ fastapi dev main.py

```

////

If a client tries to send some extra data, they will receive an **error** response.

For example, if the client tries to send the form fields:

* `username`: `Rick`
* `password`: `Portal Gun`
* `extra`: `Mr. Poopybutthole`

They will receive an error response telling them that the field `extra` is not allowed:

```json
{
    "detail": [
        {

Let's imagine that you have a database `fake_db` that only receives JSON compatible data.

For example, it doesn't receive `datetime` objects, as those are not compatible with JSON.

So, a `datetime` object would have to be converted to a `str` containing the data in <a href="https://en.wikipedia.org/wiki/ISO_8601" class="external-link" target="_blank">ISO format</a>.

If a client tries to send some **extra cookies**, they will receive an **error** response.

Poor cookie banners with all their effort to get your consent for the <abbr title="This is another joke. Don't pay attention to me. Have some coffee for your cookie. ☕">API to reject it</abbr>. 🍪