en	Control Frames
zh-hans	控制帧

en	Control frames are small (less than 128 bytes) messages entirely contained in an individual WebSocket frame. They may be sent at any time by either peer on an established connection, and can appear in between continuation frames for a message. There are three types of control frames: ping, pong, and close.
zh-hans	控制帧是小型消息（小于 128 字节），完全包含在单个 WebSocket 帧中。已建立连接的任意一端可以在任何时间发送控制帧，并且控制帧可以出现在消息的连续帧之间。控制帧分为三种类型：ping、pong 和 close。

en	A sent ping indicates a request that the sender wants to receive a pong. A pong is a response to a ping. Pongs may be sent unsolicited, at any time. One use for an unsolicited pong is to inform the remote peer that the session is still active after a long period of inactivity. A close frame indicates that the remote peer wishes to close the WebSocket connection. The connection is considered gracefully closed when each side has sent and received a close frame.
zh-hans	发送 ping 表示发送方希望收到 pong 响应。pong 是对 ping 的回复，也可以在任何时候主动发送。主动发送 pong 的一个用途是，在长时间没有数据传输时，告知远端对端连接仍然活跃。close 帧表示对端请求关闭 WebSocket 连接。当双方都完成发送并接收到 close 帧后，连接视为已正常关闭。

en	During read operations, Beast automatically reads and processes control frames. If a control callback is registered, the callback is notified of the incoming control frame. The implementation will respond to pings automatically. The receipt of a close frame initiates the WebSocket close procedure, eventually resulting in the error code [link beast.ref.boost__beast__websocket__error `error::closed`] being delivered to the caller in a subsequent read operation, assuming no other error takes place.
zh-hans	在执行读取操作期间，Beast 会自动读取并处理控制帧。如果注册了控制回调函数，该回调会收到传入控制帧的通知。实现会自动响应 ping。当收到 close 帧时，会触发 WebSocket 关闭流程，最终在后续的读取操作中（假设没有发生其他错误）向调用方传递错误码 [link beast.ref.boost__beast__websocket__error error::closed]。

en	A consequence of this automatic behavior is that caller-initiated read operations can cause socket writes. However, these writes will not compete with caller-initiated write operations. For the purposes of correctness with respect to the stream invariants, caller-initiated read operations still only count as a read. This means that callers can have a simultaneously active read, write, and ping/pong operation in progress, while the implementation also automatically handles control frames.
zh-hans	这种自动行为会导致一个后果：调用方发起的读操作，可能触发套接字写入。但这类写入不会与调用方主动发起的写操作产生竞争。从流不变性的正确性来看，调用方发起的读操作仍只视为读取。这意味着调用方可同时进行读、写和 ping/pong 操作，同时实现也会在后台自动处理控制帧。

en	Control Callback
zh-hans	控制回调

en	Ping, pong, and close messages are control frames which may be sent at any time by either peer on an established WebSocket connection. They are sent using the functions [link beast.ref.boost__beast__websocket__stream.ping `ping`], [link beast.ref.boost__beast__websocket__stream.pong `pong`]. and [link beast.ref.boost__beast__websocket__stream.close `close`]. To be notified of control frames, callers may register a ['control callback] using [link beast.ref.boost__beast__websocket__stream.control_callback `control_callback`]. The object provided with this option should be callable with the following signature:
zh-hans	ping、pong 和 close 消息属于控制帧，在已建立的 WebSocket 连接上，任何一端都可以随时发送。它们分别通过 [link beast.ref.boost__beast__websocket__stream.ping `ping`]、[link beast.ref.boost__beast__websocket__stream.pong `pong`] 和 [link beast.ref.boost__beast__websocket__stream.close `close`] 函数发送。若要接收控制帧的通知，调用方可通过 [link beast.ref.boost__beast__websocket__stream.control_callback `control_callback`] 注册一个控制回调。该选项提供的对象应满足以下签名要求：

en	When a control callback is registered, it will be invoked for all pings, pongs, and close frames received through either synchronous read functions or asynchronous read functions. The type of frame and payload text are passed as parameters to the control callback. If the frame is a close frame, the close reason may be obtained by calling [link beast.ref.boost__beast__websocket__stream.reason `reason`].
zh-hans	当注册控制回调后，无论是通过同步读函数还是异步读函数接收到的所有 ping、pong 和 close 帧，都会触发该回调。帧类型和有效载荷文本会作为参数传递给控制回调。如果帧为 close 帧，可通过调用 [link beast.ref.boost__beast__websocket__stream.reason `reason`] 获取关闭原因。

en	Unlike regular completion handlers used in calls to asynchronous initiation functions, the control callback only needs to be set once. The callback is not reset after being called. The same callback is used for both synchronous and asynchronous reads. The callback is passive; in order to be called, a stream read operation must be active.
zh-hans	与异步发起函数调用中使用的普通完成处理器不同，控制回调只需设置一次，调用后不会被重置。该回调同时用于同步和异步读取。回调是“被动”的——必须有一个流读取操作处于活动状态，回调才会被触发。

en	When an asynchronous read function receives a control frame, the
zh-hans	当异步读函数收到控制帧时，

en	Close Frames
zh-hans	关闭帧

en	The WebSocket protocol defines a procedure and control message for initiating a close of the session. In this procedure, a host requests the close by sending a [@https://tools.ietf.org/html/rfc6455#section-5.5.1 ['close frame]]. To request a close use a close function such as [link beast.ref.boost__beast__websocket__stream.close.overload2 `close`] or [link beast.ref.boost__beast__websocket__stream.async_close `async_close`]:
zh-hans	WebSocket 协议定义了启动会话关闭的过程和控制消息。在该过程中，主机通过发送 [@https://tools.ietf.org/html/rfc6455#section-5.5.1 关闭帧] 来请求关闭。若要请求关闭，可使用 `close` 或 `async_close` 等关闭函数：

en	The close function will send a close frame, read and discard incoming message data until receiving a close frame, and then shut down the underlying connection before returning.
zh-hans	关闭函数会发送关闭帧，然后读取并丢弃所有传入的消息数据，直到收到关闭帧为止，最后在返回之前关闭底层连接。

en	When a close frame is received by during a read operation, the implementation will automatically respond with a close frame and then shut down the underlying connection before returning. In this case, the read operation will complete with the code [link beast.ref.boost__beast__websocket__error `error::closed`]. This indicates to the caller that the connection has been closed cleanly.
zh-hans	当读操作期间收到关闭帧时，实现会自动回复一个关闭帧，然后在返回之前关闭底层连接。在这种情况下，读操作会以错误码 [link beast.ref.boost__beast__websocket__error `error::closed`] 完成，这表示连接已被正常关闭。

en	To receive the
zh-hans	要接受

en	Auto-fragment
zh-hans	自动分帧

en	To ensure timely delivery of control frames, large outgoing messages can be broken up into smaller sized frames. The automatic fragment option turns on this feature, and the write buffer size option determines the maximum size of the fragments:
zh-hans	为确保控制帧的及时传递，可以将较大的出站消息拆分为较小的帧。自动分片选项用于开启此功能，而写入缓冲区大小选项则决定分片的最大大小：