### Required, can be `None` { #required-can-be-none }

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but simply do not declare a default value:

  /** Returns this address's certificate pinner, or null if this is not an HTTPS address. */
  @get:JvmName("certificatePinner") val certificatePinner: CertificatePinner?,
  /** Returns the client's proxy authenticator. */
  @get:JvmName("proxyAuthenticator") val proxyAuthenticator: Authenticator,
  /**
   * Returns this address's explicitly-specified HTTP proxy, or null to delegate to the

            } else {

                /* On NT without Unicode the fileNameLength
                 * includes the '\0' whereas on win98 it doesn't. I
                 * guess most clients only support non-unicode so
                 * they don't run into this.
                 */

                /* UPDATE: Maybe not! Could this be a Unicode alignment issue. I hope

<img src="/img/tutorial/websockets/image05.png">

## Обработка отключений и работа с несколькими клиентами { #handling-disconnections-and-multiple-clients }

Если веб-сокет соединение закрыто, то `await websocket.receive_text()` вызовет исключение `WebSocketDisconnect`, которое можно поймать и обработать как в этом примере:

## Recapitulação { #recap }

Agora você pode obter o usuário atual diretamente na sua *função de operação de rota*.

Já estamos na metade do caminho.

Só precisamos adicionar uma *operação de rota* para que o usuário/cliente realmente envie o `username` e `password`.

            doColumn("_id");
        }

        public void columnAccessType() {
            doColumn("accessType");
        }

        public void columnClientIp() {
            doColumn("clientIp");
        }

        public void columnHitCount() {
            doColumn("hitCount");
        }

        public void columnHitCountRelation() {
            doColumn("hitCountRelation");
        }

 * Provides common functionality for handling initialization parameters,
 * content length checks, and default method implementations.
 * It defines the basic structure and configuration options for crawler clients.
 */
public abstract class AbstractCrawlerClient implements CrawlerClient {

    private static final Logger logger = LogManager.getLogger(AbstractCrawlerClient.class);

/// tip | Tipp

Bedenken Sie, dass JSON nur `str` als Schlüssel unterstützt.

Aber Pydantic hat automatische Datenkonvertierung.

Das bedeutet, dass Ihre API-Clients nur Strings senden können, aber solange diese Strings nur Zahlen enthalten, wird Pydantic sie konvertieren und validieren.

Und das `dict`, welches Sie als `weights` erhalten, wird `int`-Schlüssel und `float`-Werte haben.

	biggerBufMax = maxBufferSize

	// If there is a queue, merge up to this many messages.
	maxMergeMessages = 50

	// clientPingInterval will ping the remote handler every 15 seconds.
	// Clients disconnect when we exceed 2 intervals.
	clientPingInterval = 15 * time.Second

	// Deadline for single (non-streaming) requests to complete.
	// Used if no deadline is provided on context.

        .Builder()
        .addTrustedCertificate(clientCa.certificate)
        .heldCertificate(serverCertificate)
        .build()
    server.useHttps(serverHandshakeCertificates.sslSocketFactory(), false)
    server.enqueue(MockResponse().setBody("abc"))
    server.requestClientAuth()
    val clientCertificate =
      HeldCertificate
        .Builder()
        .signedBy(clientCa)
        .build()