keep-alive

基本解釋

In order to maintain presence, the chat application can send keep-alive messages on the websocket to prevent it being closed due to an idle timeout.
為了保持存在的狀態(tài)，聊天應用要發(fā)送“連接保持（Keep Alive）”的消息給WebSocket，來避免該連接因為閑置超時而關閉。
Since clients do not wish to be forcefully disconnected, they will automatically send a keep-alive message if the connection is inactive for the number of seconds specified by this parameter.
由于客戶機不希望強制斷開連接，因此，當連接閑置的時間為此參數(shù)指定的秒數(shù)時，客戶機將自動發(fā)送 keep-alive 消息。
Persistent connections specify that an outgoing HTTP response should use a persistent (keep-alive) connection instead of a connection that closes after one request or response exchange occurs.
持久連接指定傳出的 HTTP 響應應該使用持久（保持活動狀態(tài)）連接，而不是在請求或響應交換后關閉的連接。

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