事件：'unknownProtocol'

¥Event: 'unknownProtocol'

• socket <stream.Duplex>

当连接的客户端无法协商允许的协议（即 HTTP/2 或 HTTP/1.1）时，则会触发 'unknownProtocol' 事件。事件句柄接收套接字进行处理。如果没有为该事件注册监听器，则连接将终止。可以使用传给 http2.createSecureServer() 的 'unknownProtocolTimeout' 选项指定超时。参见 兼容性接口。

¥The 'unknownProtocol' event is emitted when a connecting client fails to negotiate an allowed protocol (i.e. HTTP/2 or HTTP/1.1). The event handler receives the socket for handling. If no listener is registered for this event, the connection is terminated. A timeout may be specified using the 'unknownProtocolTimeout' option passed to http2.createSecureServer(). See the Compatibility API.