3.4.5.1.1.2 Sending a KeepAlive-GET-Response with Status code 400
If the protocol version does not equal the required KeepAlive version value (see section 2.2.3.1.1.2), the server SHOULD<32> sends a KeepAlive-GET-Response message with a Response-Status-Line (see section 2.2.2.3.1) that contains a status code of 400 and phrase of "Bad Request".
The KeepAlive-GET-Response message with Status code of 400 and phrase of "Bad Request" can also be sent on protocol errors.
The KeepAlive-GET-Response MUST be sent on the GET session. The KeepAlive virtual connection MUST be closed (see section 3.3.4.2).
The server sets ServerOKtoSend to FALSE.