```

/// note | Technical Details

You could also use `from starlette.requests import Request` and `from starlette.responses import JSONResponse`.

**FastAPI** provides the same `starlette.responses` as `fastapi.responses` just as a convenience for you, the developer. But most of the available responses come directly from Starlette. The same with `Request`.

///

    enforce strict null checks.

 *  New: The response message is now non-null. This is the "Not Found" in the
    status line "HTTP 404 Not Found". If you are building responses
    programmatically (with `new Response.Builder()`) you must now always supply
    a message. An empty string `""` is permitted. This value was never null on
    responses returned by OkHttp itself, and it was an old mistake to permit

     */
    void setInitParameterMap(Map<String, Object> params);

    /**
     * Executes a request and returns the response data.
     *
     * @param data the request data to be executed
     * @return the response data from the executed request
     */
    ResponseData execute(RequestData data);

    /**
     * Closes the crawler client and releases any resources associated with it.

        } else if (compound && this.nextCommand == 0 && this.readSize > 0) {
            // Apply compound response handling as per MS-SMB2 3.2.5.1.9 - correct for both compound and single responses
            // 3.2.5.1.9 Handling Compounded Responses
            // The final response in the compounded response chain will have NextCommand equal to 0,

<img src="/img/tutorial/websockets/image01.png">

Puedes escribir mensajes en el cuadro de entrada y enviarlos:

<img src="/img/tutorial/websockets/image02.png">

Y tu aplicación **FastAPI** con WebSockets responderá de vuelta:

<img src="/img/tutorial/websockets/image03.png">

Puedes enviar (y recibir) muchos mensajes:

<img src="/img/tutorial/websockets/image04.png">

Y todos usarán la misma conexión WebSocket.

Notice that the *path operations* define the models they use for request payload and response payload, using the models `Item` and `ResponseMessage`.

### API Docs { #api-docs }

If you go to `/docs`, you will see that it has the **schemas** for the data to be sent in requests and received in responses:

<img src="/img/tutorial/generate-clients/image01.png">

En este caso, podrías querer documentar cómo esa API externa *debería* verse. Qué *path operation* debería tener, qué cuerpo debería esperar, qué response debería devolver, etc.

## Una aplicación con callbacks

Veamos todo esto con un ejemplo.

    Note over client,operation: Response is already sent, can't change it anymore
    opt Tasks
        operation -->> tasks: Send background tasks
    end
    opt Raise other exception
        tasks -->> tasks: Handle exceptions in the background task code
    end
```

/// info

Only **one response** will be sent to the client. It might be one of the error responses or it will be the response from the *path operation*.

        if (this.ptype == 2 || this.ptype == 3) { /* Response or Fault */
            this.alloc_hint = buf.dec_ndr_long();
            buf.dec_ndr_short(); /* context id */
            buf.dec_ndr_short(); /* cancel count */
        }
        if (this.ptype == 3 || this.ptype == 13) { /* Fault */
            this.result = buf.dec_ndr_long();
        } else { /* Bind_ack or Response */
            decode_out(buf);
        }
    }

        });
        return asJson(new ApiResponse().status(Status.OK).result());
    }

    /**
     * Creates an edit body from a job log entity for API responses.
     *
     * @param entity the job log entity to convert
     * @return edit body containing the entity data
     */
    protected EditBody createEditBody(final JobLog entity) {