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Version: 4.x

常见问题

以下是有关 Socket.IO 的常见问题列表：

¥Here is a list of common questions about Socket.IO:

有些东西不能正常工作，请帮忙？​

¥Something does not work properly, please help?

请检查 故障排除指南。

¥Please check the Troubleshooting guide.

它在幕后是如何工作的？​

¥How does it work under the hood?

Socket.IO 连接可以通过不同的底层传输建立：

¥The Socket.IO connection can be established with different low-level transports:

Socket.IO 将自动选择最佳可用选项，具体取决于：

¥Socket.IO will automatically pick the best available option, depending on:

  • 浏览器的功能（参见 此处 和 此处）

    ¥the capabilities of the browser (see here and here)

  • 网络（某些网络阻止 WebSocket 和/或 WebTransport 连接）

    ¥the network (some networks block WebSocket and/or WebTransport connections)

你可以在 "工作原理" 节 中找到更多详细信息。

¥You can find more detail about that in the "How it works" section.

Socket.IO 相对于普通 WebSocket 提供了哪些功能？​

¥What are the features provided by Socket.IO over plain WebSocket?

WebSocket 太棒了！不完全是。它们提供了一种在客户端和服务器之间传输数据的有效方法。优点包括：

¥WebSockets are awesome! No, really. They provide an efficient way for transferring data between a client and a server. Among the advantages:

  • 你不需要依赖定期轮询从服务器获取数据

    ¥you don't need to rely on periodic polling to fetch data from the server

  • 向服务器发送数据时无需重复发送所有 HTTP 标头

    ¥you don't need to repeatedly send all the HTTP headers when sending data to the server

这使得它们非常适合低延迟和数据密集型应用，例如游戏、聊天、协作解决方案......

¥Which make them perfect for low-latency and data-intensive applications like games, chats, collaborative solutions...

话虽这么说，WebSocket 也是相当底层的，使用 WebSocket 开发实时应用通常需要在它们之上添加一个附加层：

¥That being said, WebSockets are also pretty low-level and developing a realtime applications with WebSockets often requires an additional layer over them:

  • 回退到 HTTP 长轮询，以防无法建立 WebSocket 连接

    ¥fallback to HTTP long-polling, in case the WebSocket connection can't be established

  • 自动重新连接，以防 WebSocket 连接关闭

    ¥automatic reconnection, in case the WebSocket connection gets closed

  • 确认，发送一些数据并期待对方的响应

    ¥acknowledgements, to send some data and expect a response from the other side

  • 向所有或部分连接的客户端广播

    ¥broadcast to all or to a subset of connected clients

  • 扩展到服务器的多个实例

    ¥scale up to multiple instances of the server

  • 连接恢复，用于短时间的断开连接

    ¥connection recovery, for short periods of disconnection

正如你可能已经猜到的，这个附加层是由 Socket.IO 库实现的。

¥As you might have guessed, this additional layer is implemented by the Socket.IO library.

什么是 WebTransport？​

¥What is WebTransport?

简而言之，WebTransport 是 WebSocket 的替代方案，它修复了困扰 队头阻塞 等 WebSocket 的几个性能问题。

¥In short, WebTransport is an alternative to WebSocket which fixes several performance issues that plague WebSockets like head-of-line blocking.

如果你想了解有关此新 Web API（于 2022 年 1 月包含在 Chrome 中，并于 2023 年 6 月包含在 Firefox 中）的更多信息，请检查以下链接：

¥If you want more information about this new web API (which was included in Chrome in January 2022 and in Firefox in June 2023), please check those links:

note

默认情况下，Socket.IO 中未启用对 WebTransport 的支持，因为它需要安全上下文 (HTTPS)。如果你想使用 WebTransport，请检查 专用教程。

¥Support for WebTransport is not enabled by default in Socket.IO, as it requires a secure context (HTTPS). Please check the dedicated tutorial if you want to play with WebTransport.

Socket.IO 是否存储消息？​

¥Does Socket.IO store the messages?

Socket.IO 服务器不存储任何消息。

¥The Socket.IO server does not store any message.

你的应用有责任为当前未连接的客户端保留这些消息。

¥It is the duty of your application to persist those messages somewhere for the clients that are not currently connected.

tip

话虽这么说，如果你启用 连接状态恢复功能，Socket.IO 会将消息存储一小段时间。

¥That being said, Socket.IO will store the messages for a brief period of time if you enable the Connection state recovery feature.

Socket.IO 的交付保证是什么？​

¥What are the delivery guarantees of Socket.IO?

Socket.IO 确实保证消息排序，无论使用哪种底层传输（即使在两种传输之间切换时）。

¥Socket.IO does guarantee message ordering, no matter which low-level transport is used (even when switching between two transports).

此外，默认情况下，Socket.IO 提供最多一次传送保证（也称为 "即发即忘"），这意味着在某些情况下消息可能会丢失并且不会尝试重试。

¥Moreover, by default Socket.IO provides an at most once guarantee of delivery (also known as "fire and forget"), which means that under certain circumstances a message might get lost and no retry will be attempted.

有关此 此处 的更多信息。

¥More information about this here.

如何识别给定用户？​

¥How to identify a given user?

Socket.IO 中没有用户的概念。

¥There is no concept of user in Socket.IO.

你的应用有责任将给定的 Socket.IO 连接链接到用户账户。

¥It is the duty of your application to link a given Socket.IO connection to a user account.

对于 Node.js 应用，你可以：

¥For Node.js applications, you can for example:

我在哪里可以找到变更日志？​

¥Where can I find the changelog?

请参阅 此处。

¥Please see here.