<!--- Provide a general summary of the issue in the Title above -->

## Expected Behavior
<!--- If you're describing a bug, tell us what should happen -->
<!--- If you're suggesting a change/improvement, tell us how it should work -->

## Current Behavior
<!--- If describing a bug, tell us what happens instead of the expected behavior -->
<!--- If suggesting a change/improvement, explain the difference from current behavior -->

      isTlsFallback = isTlsFallback,
    )

  override fun connectTcp(): ConnectResult {
    check(rawSocket == null) { "TCP already connected" }

    var success = false

    // Tell the call about the connecting call so async cancels work.
    call.plansToCancel += this
    try {
      call.eventListener.connectStart(call, route.socketAddress, route.proxy)

# OpenAPI Webhooks { #openapi-webhooks }

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

   * requires us to have a DNS address for both hosts, which only happens after route planning. We
   * can't coalesce connections that use a proxy, since proxies don't tell us the origin server's IP
   * address.
   */
  private fun routeMatchesAny(candidates: List<Route>): Boolean =
    candidates.any {
      it.proxy.type() == Proxy.Type.DIRECT &&

In general, ASGI middlewares are classes that expect to receive an ASGI app as the first argument.

So, in the documentation for third-party ASGI middlewares they will probably tell you to do something like:

```Python
from unicorn import UnicornMiddleware

app = SomeASGIApp()

new_app = UnicornMiddleware(app, some_config="rainbow")
```

There are many situations in which you need to notify an error to a client that is using your API.

This client could be a browser with a frontend, a code from someone else, an IoT device, etc.

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.

When you install FastAPI with something like `pip install "fastapi[standard]"` you already get `uvicorn[standard]` as well.

///

## Run the Server Program { #run-the-server-program }

If you installed an ASGI server manually, you would normally need to pass an import string in a special format for it to import your FastAPI application:

/// tip

If you have strict type checks in your editor, mypy, etc, you can declare the function return type as `Any`.

That way you tell the editor that you are intentionally returning anything. But FastAPI will still do the data documentation, validation, filtering, etc. with the `response_model`.

///

### `response_model` Priority { #response-model-priority }

But if you know that you won't need to use the dependency after returning from the *path operation function*, you can use `Depends(scope="function")` to tell FastAPI that it should close the dependency after the *path operation function* returns, but **before** the **response is sent**.

{* ../../docs_src/dependencies/tutorial008e_an_py39.py hl[12,16] *}

<div class="termy">

```console
$ python -m venv .venv
```

</div>

/// details | What that command means

* `python`: use the program called `python`
* `-m`: call a module as a script, we'll tell it which module next
* `venv`: use the module called `venv` that normally comes installed with Python
* `.venv`: create the virtual environment in the new directory `.venv`

///

////

//// tab | `uv`