.Builder()
        .webSocketUpgrade(serverListener)
        .build(),
    )
    val webSocket: WebSocket = newWebSocket()
    clientListener.assertOpen()
    val server = serverListener.assertOpen()
    webSocket.send("Hello, WebSockets!")
    serverListener.assertTextMessage("Hello, WebSockets!")
    closeWebSockets(webSocket, server)
  }

  @Test
  fun binaryMessage() {
    webServer.enqueue(

# WebSockets { #websockets }

**FastAPI**で[WebSockets](https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API)が使用できます。

## `websockets`のインストール { #install-websockets }

[仮想環境](../virtual-environments.md)を作成し、それを有効化してから、「WebSocket」プロトコルを簡単に使えるようにするPythonライブラリの`websockets`をインストールしてください。

<div class="termy">

```console
$ pip install websockets

---> 100%
```

</div>

## WebSockets クライアント { #websockets-client }

    webSocket: WebSocket,
    code: Int,
    reason: String,
  ) {
    Platform.get().log("[WS $name] onClosed $code", Platform.INFO, null)
    val delegate = delegate
    if (delegate != null) {
      this.delegate = null
      delegate.onClosed(webSocket, code, reason)
    } else {
      events.add(Closed(code, reason))
    }
  }

  override fun onFailure(
    webSocket: WebSocket,
    t: Throwable,

app = FastAPI()


@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket, session: SessionDep):
    await websocket.accept()
    for item in session:
        await websocket.send_text(f"{item}")


@app.websocket("/ws-broken")
async def websocket_endpoint_broken(websocket: WebSocket, session: BrokenSessionDep):
    await websocket.accept()
    for item in session:

# WebSocket 테스트하기 { #testing-websockets }

같은 `TestClient`를 사용하여 WebSocket을 테스트할 수 있습니다.

이를 위해 `with` 문에서 `TestClient`를 사용하여 WebSocket에 연결합니다:

{* ../../docs_src/app_testing/tutorial002_py310.py hl[27:31] *}

/// note

자세한 내용은 Starlette의 [WebSocket 테스트](https://www.starlette.dev/testclient/#testing-websocket-sessions) 문서를 확인하세요.

]

app = FastAPI()


@app.websocket("/function-scope")
async def function_scope(websocket: WebSocket, session: SessionFuncDep) -> Any:
    await websocket.accept()
    await websocket.send_json({"is_open": session.open})


@app.websocket("/request-scope")
async def request_scope(websocket: WebSocket, session: SessionRequestDep) -> Any:
    await websocket.accept()
    await websocket.send_json({"is_open": session.open})

          text: String,
        ) {
          webSocket.send(text)
        }

        override fun onClosing(
          webSocket: WebSocket,
          code: Int,
          reason: String,
        ) {
          webSocket.close(1000, null)
          latch.countDown()
        }

        override fun onFailure(
          webSocket: WebSocket,
          t: Throwable,
          response: Response?,

  @Override public void onMessage(WebSocket webSocket, String text) {
    System.out.println("onMessage: " + text);
  }

  @Override public void onClosing(WebSocket webSocket, int code, String reason) {
    webSocket.close(1000, null);
    System.out.println("onClose (" + code + "): " + reason);
  }

  @Override public void onFailure(WebSocket webSocket, Throwable t, Response response) {

    client.dispatcher().executorService().shutdown();
  }

  @Override public void onOpen(WebSocket webSocket, Response response) {
    webSocket.send("Hello...");
    webSocket.send("...World!");
    webSocket.send(ByteString.decodeHex("deadbeef"));
    webSocket.close(1000, "Goodbye, World!");
  }

  @Override public void onMessage(WebSocket webSocket, String text) {
    System.out.println("MESSAGE: " + text);
  }

# WebSockets

When defining WebSockets, you normally declare a parameter of type `WebSocket` and with it you can read data from the client and send data to it.

Read more about it in the [FastAPI docs for WebSockets](https://fastapi.tiangolo.com/advanced/websockets/)

It is provided directly by Starlette, but you can import it from `fastapi`:

```python
from fastapi import WebSocket
```

/// tip