# WebSockets { #websockets }

您可以在 **FastAPI** 中使用 [WebSockets](https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API)。

## 安装 `websockets` { #install-websockets }

请确保您创建一个[虚拟环境](../virtual-environments.md)、激活它，并安装 `websockets`（一个让使用“WebSocket”协议更容易的 Python 库）：

<div class="termy">

```console
$ pip install websockets

---> 100%
```

</div>

## WebSockets 客户端 { #websockets-client }

<?xml version="1.0" encoding="UTF-8" ?>

<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
  version="2.0">
    
  <description>JSTL 1.1 functions library</description>
  <display-name>JSTL functions</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>fe</short-name>

   * may be sent after response headers or body bytes have been received.
   *
   * Though any call may be initiated as a duplex call, only web servers that are specially
   * designed for this nonstandard interaction will use it. As of 2019-01, the only widely-used
   * implementation of this pattern is [gRPC][grpc].
   *

 * loader and prevent it from being garbage collected. This poses a problem for environments where
 * you want to throw away the class loader. For example, dynamically reloading a web application or
 * unloading an OSGi bundle.
 *
 * <p>{@code com.google.common.base.FinalizableReferenceQueue} loads this class in its own class

						</la:link></li>
				</ul>
			</div>
		</nav>
	</header>
	<c:if test="${!chatPage}">
	<div id="searchOptions" class="collapse">
		<div class="container">
			<jsp:include page="/WEB-INF/view/searchOptions.jsp" />
			<div>
				<button type="button" class="btn btn-light" id="searchOptionsClearButton">
					<la:message key="labels.search_options_clear" />
				</button>

						</la:link></li>
				</ul>
			</div>
		</nav>
	</header>
	<c:if test="${!chatPage}">
	<div id="searchOptions" class="collapse">
		<div class="container">
			<jsp:include page="/WEB-INF/view/searchOptions.jsp" />
			<div>
				<button type="button" class="btn btn-light" id="searchOptionsClearButton">
					<la:message key="labels.search_options_clear" />
				</button>

		HTTPStatusCode: http.StatusBadRequest,
	},
	ErrSTSWebIdentityExpiredToken: {
		Code:           "ExpiredToken",
		Description:    "The web identity token that was passed is expired or is not valid. Get a new identity token from the identity provider and then retry the request.",
		HTTPStatusCode: http.StatusBadRequest,
	},
	ErrSTSClientGrantsExpiredToken: {

/// note | 技术细节

这些代理相关的请求头包括：

* [X-Forwarded-For](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-For)
* [X-Forwarded-Proto](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Proto)
* [X-Forwarded-Host](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Host)

///

### 启用代理转发的请求头 { #enable-proxy-forwarded-headers }

   * thread keeps an indirect strong reference to the queue in ReferenceMap, which keeps the
   * Finalizer running, and as a result, the application class loader can never be reclaimed.
   *
   * This means that dynamically loaded web applications and OSGi bundles can't be unloaded.
   *
   * If the library is loaded in an application class loader, we try to break the cycle by loading
   * Finalizer in its own independent class loader:
   *

# Server-Sent Events（SSE） { #server-sent-events-sse }

你可以使用 Server-Sent Events（SSE）把資料串流傳送給用戶端。

這與[串流 JSON Lines](stream-json-lines.md)類似，但使用瀏覽器原生支援、透過 [`EventSource` API](https://developer.mozilla.org/en-US/docs/Web/API/EventSource) 的 `text/event-stream` 格式。

/// info

在 FastAPI 0.135.0 新增。

///

## 什麼是 Server-Sent Events？ { #what-are-server-sent-events }

SSE 是一種透過 HTTP 從伺服器向用戶端串流傳送資料的標準。