[providers]
  [providers.file]
    filename = "routes.toml"
```

This tells Traefik to listen on port 9999 and to use another file `routes.toml`.

/// tip

We are using port 9999 instead of the standard HTTP port 80 so that you don't have to run it with admin (`sudo`) privileges.

///

Now create that other file `routes.toml`:

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

  val responses = mutableListOf<Response>()
  val routes = mutableListOf<Route>()

  fun onlyResponse() = responses.single()

  fun onlyRoute() = routes.single()

  @Throws(IOException::class)
  override fun authenticate(
    route: Route?,
    response: Response,
  ): Request? {
    if (route == null) throw NullPointerException("route == null")
    responses += response
    routes += route

     *
     * @return true if the problem collector has overflowed and some problems were not preserved
     */
    boolean problemsOverflow();

    /**
     * Reports a problem: always maintains the counters, but whether problem is preserved in memory, depends on
     * implementation and its configuration.
     *
     * @param problem the problem to report
     * @return {@code true} if passed problem is preserved by this call.

* `summary`: A short summary of the API.
* `description`: The description of your API, this can include markdown and will be shown in the docs.
* `routes`: A list of routes, these are each of the registered *path operations*. They are taken from `app.routes`.

/// info

The parameter `summary` is available in OpenAPI 3.1.0 and above, supported by FastAPI 0.99.0 and above.

///

{* ../../docs_src/first_steps/tutorial001.py hl[1] *}

`FastAPI` est une classe Python qui fournit toutes les fonctionnalités nécessaires au lancement de votre API.

/// note | Détails techniques

`FastAPI` est une classe héritant directement de `Starlette`.

Vous pouvez donc aussi utiliser toutes les fonctionnalités de <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a> depuis `FastAPI`.

    val selection = routeSelector.next()
    dns.assertRequests(uriHost)
    val routes = selection.routes
    assertRoute(routes[0], address, Proxy.NO_PROXY, dns.lookup(uriHost, 0), uriPort)
    assertRoute(routes[1], address, Proxy.NO_PROXY, dns.lookup(uriHost, 1), uriPort)
    assertThat(selection.next()).isSameAs(routes[0])
    assertThat(selection.next()).isSameAs(routes[1])
    assertThat(selection.hasNext()).isFalse()

    planToReplace: ConnectPlan? = null,
    routes: List<Route>? = null,
  ): ReusePlan? {
    val result =
      connectionPool.callAcquirePooledConnection(
        doExtensiveHealthChecks = connectionUser.doExtensiveHealthChecks(),
        address = address,
        connectionUser = connectionUser,
        routes = routes,
        requireMultiplexed = planToReplace != null && planToReplace.isReady,

      pingIntervalMillis = pingIntervalMillis,
      retryOnConnectionFailure = retryOnConnectionFailure,
      user = user,
      routePlanner = routePlanner,
      route = route,
      routes = routes,
      attempt = attempt,
      tunnelRequest = tunnelRequest,
      connectionSpecIndex = connectionSpecIndex,
      isTlsFallback = isTlsFallback,
    )

  override fun connectTcp(): ConnectResult {

& 👈 🔢 `get_openapi()` 📨 🔢:

* `title`: 🗄 📛, 🎦 🩺.
* `version`: ⏬ 👆 🛠️, ✅ `2.5.0`.
* `openapi_version`: ⏬ 🗄 🔧 ⚙️. 🔢, ⏪: `3.0.2`.
* `description`: 📛 👆 🛠️.
* `routes`: 📇 🛣, 👫 🔠 ® *➡ 🛠️*. 👫 ✊ ⚪️➡️ `app.routes`.

## 🔑 🔢

⚙️ ℹ 🔛, 👆 💪 ⚙️ 🎏 🚙 🔢 🏗 🗄 🔗 & 🔐 🔠 🍕 👈 👆 💪.

   *
   * If [routes] is non-null these are the resolved routes (ie. IP addresses) for the connection.
   * This is used to coalesce related domains to the same HTTP/2 connection, such as `square.com`
   * and `square.ca`.
   */
  fun callAcquirePooledConnection(
    doExtensiveHealthChecks: Boolean,
    address: Address,
    connectionUser: ConnectionUser,
    routes: List<Route>?,
    requireMultiplexed: Boolean,