SOME/IP報文格式-Message Type
Message Type [8 Bit]
The Message Type ?eld is used to differentiate different types of messages and shall contain the following values：
Message Type用來區別不同類型的message，且應當包含如下的值：
| Number | Value | Description |
| 0x00 | REQUEST | A request expecting a response (even void) |
| 0x01 | REQUEST_NO_RETURN | A ?re&forget request |
| 0x02 | NOTIFICATION | A request of a noti?cation/event callback expecting no response |
| 0x40 | REQUEST_ACK | Acknowledgment for REQUEST (optional) |
| 0x41 | REQUEST_NO_RETURN_ACK | Acknowledgment for REQUEST_NO_RETURN (informational) |
| 0x42 | NOTIFICATION_ACK | Acknowledgment for NOTIFICATION (informational) |
| 0x80 | RESPONSE | The response message |
| 0x81 | ERROR | The response containing an error |
| 0xC0 | RESPONSE_ACK | The Acknowledgment for RESPONSE (informational) |
| 0xC1 | ERROR_ACK | Acknowledgment for ERROR (informational) |
?Regular request (message type 0x00) will be answered by a response (message type 0x80), when no error occurred. If errors occur an error message (message type 0x81) will be sent. It is also possible to send a request that does not have a response message(message type 0x01). For updating values through noti?cation a callback interface exists (message type 0x02). 常規request （消息類型0x00）將在未發生錯誤時由response （消息類型0x80）應答。 如果發生錯誤，則會發送error消息（消息類型0x81）。 也可以發送不需要響應消息的請求（消息類型0x01）。 為了通過noti?cation更新值，存在一個callback接口（消息類型0x02）。 ?For all messages an optional acknowledgment (ACK) exists. These care is de?ned for transport protocols (i.e. UDP) that do not acknowledge a received message. ACKs are only transported when the interface speci?cation requires it. Only the usage of the REQUEST_ACK is currently speci?ed in this document. All other ACKs are currently informational and do not need to be implemented. 對于所有消息，存在可選的acknowledgment 報文（ACK）。 這是為那些并不告知收到消息的某些傳輸層協議（如UDP）而定義的。 ACK只在interface speci?cation要求時才被傳輸。 本文檔中僅規定了REQUEST_ACK的用法。 所有其他ACK現在都是信息性的，不需要實施。