{!../../../docs_src/advanced_middleware/tutorial002.py!}
```

The following arguments are supported:

* `allowed_hosts` - A list of domain names that should be allowed as hostnames. Wildcard domains such as `*.example.com` are supported for matching subdomains. To allow any hostname either use `allowed_hosts=["*"]` or omit the middleware.

If an incoming request does not validate correctly then a `400` response will be sent.

# External Links and Articles

**FastAPI** has a great community constantly growing.

There are many posts, articles, tools, and projects, related to **FastAPI**.

Here's an incomplete list of some of them.

!!! tip

### TLS mit SNI-Erweiterung

**Nur ein Prozess** im Server kann an einem bestimmten **Port** einer bestimmten **IP-Adresse** lauschen. Möglicherweise gibt es andere Prozesse, die an anderen Ports dieselbe IP-Adresse abhören, jedoch nur einen für jede Kombination aus IP-Adresse und Port.

TLS (HTTPS) verwendet standardmäßig den spezifischen Port `443`. Das ist also der Port, den wir brauchen.

### TLS with SNI Extension

**Only one process** in the server can be listening on a specific **port** in a specific **IP address**. There could be other processes listening on other ports in the same IP address, but only one for each combination of IP address and port.

TLS (HTTPS) uses the specific port `443` by default. So that's the port we would need.

    filename = "routes.toml"
```

Dadurch wird Traefik angewiesen, Port 9999 abzuhören und eine andere Datei `routes.toml` zu verwenden.

!!! tip "Tipp"
    Wir verwenden Port 9999 anstelle des Standard-HTTP-Ports 80, damit Sie ihn nicht mit Administratorrechten (`sudo`) ausführen müssen.

Erstellen Sie nun die andere Datei `routes.toml`:

```TOML hl_lines="5  12  20"
[http]
  [http.middlewares]

When you run **multiple processes** of the same API program, they are commonly called **workers**.

### Worker Processes and Ports

Remember from the docs [About HTTPS](https.md){.internal-link target=_blank} that only one process can be listening on one combination of port and IP address in a server?

This is still true.

<div style="text-align: right; margin-right: 10%;">Deon Pillsbury - <strong>Cisco</strong> <a href="https://www.linkedin.com/posts/deonpillsbury_cisco-cx-python-activity-6963242628536487936-trAp/" target="_blank"><small>(ref)</small></a></div>

---

## **Typer**, a CLI-ok FastAPI-ja

        * [FastAPI + Zeit.co = 🚀](https://paulsec.github.io/posts/fastapi_plus_zeit_serverless_fu/) by [Paul Sec](https://twitter.com/PaulWebSec).

<div style="text-align: right; margin-right: 10%;">Deon Pillsbury - <strong>Cisco</strong> <a href="https://www.linkedin.com/posts/deonpillsbury_cisco-cx-python-activity-6963242628536487936-trAp/" target="_blank"><small>(ref)</small></a></div>

---

## **Typer**, CLI-ların FastAPI-ı

<div style="text-align: right; margin-right: 10%;">Deon Pillsbury - <strong>Cisco</strong> <a href="https://www.linkedin.com/posts/deonpillsbury_cisco-cx-python-activity-6963242628536487936-trAp/" target="_blank"><small>(ref)</small></a></div>

---

## **Typer**, giao diện dòng lệnh của FastAPI